Documentation: HTTP needs update-server-info.
[git/git.git] / Documentation / tutorial.txt
CommitLineData
8c7fa247
LT
1A short git tutorial
2====================
8c7fa247
LT
3
4Introduction
5------------
6
7This is trying to be a short tutorial on setting up and using a git
2a29da7c 8repository, mainly because being hands-on and using explicit examples is
8c7fa247
LT
9often the best way of explaining what is going on.
10
11In normal life, most people wouldn't use the "core" git programs
12directly, but rather script around them to make them more palatable.
13Understanding the core git stuff may help some people get those scripts
14done, though, and it may also be instructive in helping people
15understand what it is that the higher-level helper scripts are actually
16doing.
17
18The core git is often called "plumbing", with the prettier user
2a29da7c 19interfaces on top of it called "porcelain". You may not want to use the
f35ca9ed 20plumbing directly very often, but it can be good to know what the
9755afbd
JH
21plumbing does for when the porcelain isn't flushing.
22
23The material presented here often goes deep describing how things
24work internally. If you are mostly interested in using git as a
25SCM, you can skip them during your first pass.
26
27[NOTE]
28And those "too deep" descriptions are often marked as Note.
8c7fa247 29
8431c4eb
JH
30[NOTE]
31If you are already familiar with another version control system,
32like CVS, you may want to take a look at
33link:everyday.html[Everyday GIT in 20 commands or so] first
34before reading this.
35
8c7fa247 36
2a29da7c
JH
37Creating a git repository
38-------------------------
8c7fa247 39
2a29da7c 40Creating a new git repository couldn't be easier: all git repositories start
8c7fa247
LT
41out empty, and the only thing you need to do is find yourself a
42subdirectory that you want to use as a working tree - either an empty
43one for a totally new project, or an existing working tree that you want
44to import into git.
45
2a29da7c 46For our first example, we're going to start a totally new repository from
8db9307c 47scratch, with no pre-existing files, and we'll call it `git-tutorial`.
8c7fa247 48To start up, create a subdirectory for it, change into that
8db9307c 49subdirectory, and initialize the git infrastructure with `git-init-db`:
8c7fa247 50
8db9307c 51------------------------------------------------
f2416c27
JL
52$ mkdir git-tutorial
53$ cd git-tutorial
54$ git-init-db
8db9307c 55------------------------------------------------
8c7fa247
LT
56
57to which git will reply
58
f2416c27
JL
59----------------
60defaulting to local storage area
61----------------
8c7fa247 62
837eedf4 63which is just git's way of saying that you haven't been doing anything
914328ac 64strange, and that it will have created a local `.git` directory setup for
8db9307c
JH
65your new project. You will now have a `.git` directory, and you can
66inspect that with `ls`. For your new empty project, it should show you
2a29da7c 67three entries, among other things:
8c7fa247 68
2ae6c706
JS
69 - a symlink called `HEAD`, pointing to `refs/heads/master` (if your
70 platform does not have native symlinks, it is a file containing the
71 line "ref: refs/heads/master")
8db9307c
JH
72+
73Don't worry about the fact that the file that the `HEAD` link points to
914328ac 74doesn't even exist yet -- you haven't created the commit that will
8db9307c 75start your `HEAD` development branch yet.
8c7fa247 76
8db9307c 77 - a subdirectory called `objects`, which will contain all the
8c7fa247
LT
78 objects of your project. You should never have any real reason to
79 look at the objects directly, but you might want to know that these
8db9307c
JH
80 objects are what contains all the real 'data' in your repository.
81
82 - a subdirectory called `refs`, which contains references to objects.
83
84In particular, the `refs` subdirectory will contain two other
85subdirectories, named `heads` and `tags` respectively. They do
86exactly what their names imply: they contain references to any number
87of different 'heads' of development (aka 'branches'), and to any
88'tags' that you have created to name specific versions in your
89repository.
90
91One note: the special `master` head is the default branch, which is
92why the `.git/HEAD` file was created as a symlink to it even if it
93doesn't yet exist. Basically, the `HEAD` link is supposed to always
94point to the branch you are working on right now, and you always
95start out expecting to work on the `master` branch.
96
97However, this is only a convention, and you can name your branches
98anything you want, and don't have to ever even 'have' a `master`
99branch. A number of the git tools will assume that `.git/HEAD` is
100valid, though.
101
102[NOTE]
914328ac 103An 'object' is identified by its 160-bit SHA1 hash, aka 'object name',
8db9307c 104and a reference to an object is always the 40-byte hex
914328ac 105representation of that SHA1 name. The files in the `refs`
8db9307c 106subdirectory are expected to contain these hex references
914328ac 107(usually with a final `\'\n\'` at the end), and you should thus
8db9307c 108expect to see a number of 41-byte files containing these
914328ac 109references in these `refs` subdirectories when you actually start
8db9307c 110populating your tree.
8c7fa247 111
a1d4aa74
JH
112[NOTE]
113An advanced user may want to take a look at the
114link:repository-layout.html[repository layout] document
115after finishing this tutorial.
116
2a29da7c 117You have now created your first git repository. Of course, since it's
8c7fa247
LT
118empty, that's not very useful, so let's start populating it with data.
119
120
2a29da7c
JH
121Populating a git repository
122---------------------------
8c7fa247
LT
123
124We'll keep this simple and stupid, so we'll start off with populating a
125few trivial files just to get a feel for it.
126
127Start off with just creating any random files that you want to maintain
2a29da7c 128in your git repository. We'll start off with a few bad examples, just to
8c7fa247
LT
129get a feel for how this works:
130
8db9307c 131------------------------------------------------
f2416c27
JL
132$ echo "Hello World" >hello
133$ echo "Silly example" >example
8db9307c 134------------------------------------------------
8c7fa247 135
914328ac 136you have now created two files in your working tree (aka 'working directory'), but to
8c7fa247
LT
137actually check in your hard work, you will have to go through two steps:
138
914328ac 139 - fill in the 'index' file (aka 'cache') with the information about your
2a29da7c 140 working tree state.
8c7fa247
LT
141
142 - commit that index file as an object.
143
144The first step is trivial: when you want to tell git about any changes
215a7ad1 145to your working tree, you use the `git-update-index` program. That
8c7fa247 146program normally just takes a list of filenames you want to update, but
5f3aa197 147to avoid trivial mistakes, it refuses to add new entries to the index
8c7fa247 148(or remove existing ones) unless you explicitly tell it that you're
914328ac
JH
149adding a new entry with the `\--add` flag (or removing an entry with the
150`\--remove`) flag.
8c7fa247
LT
151
152So to populate the index with the two files you just created, you can do
153
8db9307c 154------------------------------------------------
f2416c27 155$ git-update-index --add hello example
8db9307c 156------------------------------------------------
8c7fa247
LT
157
158and you have now told git to track those two files.
159
160In fact, as you did that, if you now look into your object directory,
837eedf4 161you'll notice that git will have added two new objects to the object
2a29da7c 162database. If you did exactly the steps above, you should now be able to do
8c7fa247 163
f2416c27
JL
164
165----------------
166$ ls .git/objects/??/*
167----------------
8c7fa247
LT
168
169and see two files:
170
f2416c27
JL
171----------------
172.git/objects/55/7db03de997c86a4a028e1ebd3a1ceb225be238
173.git/objects/f2/4c74a2e500f5ee1332c86b94199f52b1d1d962
174----------------
8c7fa247 175
2a29da7c 176which correspond with the objects with names of 557db... and f24c7..
8c7fa247
LT
177respectively.
178
914328ac 179If you want to, you can use `git-cat-file` to look at those objects, but
8c7fa247
LT
180you'll have to use the object name, not the filename of the object:
181
f2416c27
JL
182----------------
183$ git-cat-file -t 557db03de997c86a4a028e1ebd3a1ceb225be238
184----------------
8c7fa247 185
914328ac 186where the `-t` tells `git-cat-file` to tell you what the "type" of the
72e9340c 187object is. git will tell you that you have a "blob" object (ie just a
8c7fa247
LT
188regular file), and you can see the contents with
189
f2416c27
JL
190----------------
191$ git-cat-file "blob" 557db03
192----------------
8c7fa247 193
2a29da7c 194which will print out "Hello World". The object 557db03 is nothing
914328ac 195more than the contents of your file `hello`.
8c7fa247 196
8db9307c 197[NOTE]
914328ac
JH
198Don't confuse that object with the file `hello` itself. The
199object is literally just those specific *contents* of the file, and
200however much you later change the contents in file `hello`, the object
201we just looked at will never change. Objects are immutable.
2a29da7c 202
8db9307c
JH
203[NOTE]
204The second example demonstrates that you can
205abbreviate the object name to only the first several
206hexadecimal digits in most places.
8c7fa247
LT
207
208Anyway, as we mentioned previously, you normally never actually take a
2a29da7c
JH
209look at the objects themselves, and typing long 40-character hex
210names is not something you'd normally want to do. The above digression
215a7ad1 211was just to show that `git-update-index` did something magical, and
2a29da7c
JH
212actually saved away the contents of your files into the git object
213database.
8c7fa247 214
5f3aa197 215Updating the index did something else too: it created a `.git/index`
2a29da7c
JH
216file. This is the index that describes your current working tree, and
217something you should be very aware of. Again, you normally never worry
8c7fa247
LT
218about the index file itself, but you should be aware of the fact that
219you have not actually really "checked in" your files into git so far,
914328ac 220you've only *told* git about them.
8c7fa247 221
f35ca9ed 222However, since git knows about them, you can now start using some of the
8c7fa247
LT
223most basic git commands to manipulate the files or look at their status.
224
225In particular, let's not even check in the two files into git yet, we'll
914328ac 226start off by adding another line to `hello` first:
8c7fa247 227
8db9307c 228------------------------------------------------
f2416c27 229$ echo "It's a new day for git" >>hello
8db9307c 230------------------------------------------------
8c7fa247 231
914328ac 232and you can now, since you told git about the previous state of `hello`, ask
8c7fa247 233git what has changed in the tree compared to your old index, using the
914328ac 234`git-diff-files` command:
8c7fa247 235
914328ac 236------------
f2416c27 237$ git-diff-files
914328ac 238------------
8c7fa247 239
2a29da7c 240Oops. That wasn't very readable. It just spit out its own internal
914328ac 241version of a `diff`, but that internal version really just tells you
a05ed8cb 242that it has noticed that "hello" has been modified, and that the old object
8c7fa247
LT
243contents it had have been replaced with something else.
244
245To make it readable, we can tell git-diff-files to output the
914328ac 246differences as a patch, using the `-p` flag:
8c7fa247 247
914328ac 248------------
f2416c27 249$ git-diff-files -p
914328ac 250diff --git a/hello b/hello
2ae6c706 251index 557db03..263414f 100644
914328ac
JH
252--- a/hello
253+++ b/hello
254@@ -1 +1,2 @@
255 Hello World
256+It's a new day for git
257----
8c7fa247 258
914328ac 259i.e. the diff of the change we caused by adding another line to `hello`.
8c7fa247 260
914328ac 261In other words, `git-diff-files` always shows us the difference between
8c7fa247
LT
262what is recorded in the index, and what is currently in the working
263tree. That's very useful.
264
914328ac
JH
265A common shorthand for `git-diff-files -p` is to just write `git
266diff`, which will do the same thing.
ed616049 267
9755afbd
JH
268------------
269$ git diff
270diff --git a/hello b/hello
271index 557db03..263414f 100644
272--- a/hello
273+++ b/hello
274@@ -1 +1,2 @@
275 Hello World
276+It's a new day for git
277------------
278
8c7fa247 279
2a29da7c
JH
280Committing git state
281--------------------
8c7fa247
LT
282
283Now, we want to go to the next stage in git, which is to take the files
284that git knows about in the index, and commit them as a real tree. We do
914328ac
JH
285that in two phases: creating a 'tree' object, and committing that 'tree'
286object as a 'commit' object together with an explanation of what the
8c7fa247
LT
287tree was all about, along with information of how we came to that state.
288
914328ac 289Creating a tree object is trivial, and is done with `git-write-tree`.
8c7fa247
LT
290There are no options or other input: git-write-tree will take the
291current index state, and write an object that describes that whole
2a29da7c 292index. In other words, we're now tying together all the different
8c7fa247
LT
293filenames with their contents (and their permissions), and we're
294creating the equivalent of a git "directory" object:
295
8db9307c 296------------------------------------------------
f2416c27 297$ git-write-tree
8db9307c 298------------------------------------------------
8c7fa247
LT
299
300and this will just output the name of the resulting tree, in this case
ade75a59 301(if you have done exactly as I've described) it should be
8c7fa247 302
f2416c27
JL
303----------------
3048988da15d077d4829fc51d8544c097def6644dbb
305----------------
8c7fa247
LT
306
307which is another incomprehensible object name. Again, if you want to,
914328ac 308you can use `git-cat-file -t 8988d\...` to see that this time the object
8c7fa247 309is not a "blob" object, but a "tree" object (you can also use
914328ac 310`git-cat-file` to actually output the raw object contents, but you'll see
8c7fa247
LT
311mainly a binary mess, so that's less interesting).
312
914328ac 313However -- normally you'd never use `git-write-tree` on its own, because
8c7fa247 314normally you always commit a tree into a commit object using the
914328ac
JH
315`git-commit-tree` command. In fact, it's easier to not actually use
316`git-write-tree` on its own at all, but to just pass its result in as an
317argument to `git-commit-tree`.
8c7fa247 318
914328ac
JH
319`git-commit-tree` normally takes several arguments -- it wants to know
320what the 'parent' of a commit was, but since this is the first commit
2a29da7c 321ever in this new repository, and it has no parents, we only need to pass in
914328ac
JH
322the object name of the tree. However, `git-commit-tree`
323also wants to get a commit message
2a29da7c 324on its standard input, and it will write out the resulting object name for the
8c7fa247
LT
325commit to its standard output.
326
5990efb0
JH
327And this is where we create the `.git/refs/heads/master` file
328which is pointed at by `HEAD`. This file is supposed to contain
329the reference to the top-of-tree of the master branch, and since
330that's exactly what `git-commit-tree` spits out, we can do this
331all with a sequence of simple shell commands:
8c7fa247 332
8db9307c 333------------------------------------------------
f2416c27
JL
334$ tree=$(git-write-tree)
335$ commit=$(echo 'Initial commit' | git-commit-tree $tree)
336$ git-update-ref HEAD $commit
8db9307c 337------------------------------------------------
8c7fa247
LT
338
339which will say:
340
f2416c27
JL
341----------------
342Committing initial tree 8988da15d077d4829fc51d8544c097def6644dbb
343----------------
8c7fa247
LT
344
345just to warn you about the fact that it created a totally new commit
914328ac 346that is not related to anything else. Normally you do this only *once*
8c7fa247
LT
347for a project ever, and all later commits will be parented on top of an
348earlier commit, and you'll never see this "Committing initial tree"
349message ever again.
350
2a29da7c 351Again, normally you'd never actually do this by hand. There is a
914328ac
JH
352helpful script called `git commit` that will do all of this for you. So
353you could have just written `git commit`
ed616049
LT
354instead, and it would have done the above magic scripting for you.
355
8c7fa247 356
2a29da7c
JH
357Making a change
358---------------
8c7fa247 359
215a7ad1 360Remember how we did the `git-update-index` on file `hello` and then we
914328ac 361changed `hello` afterward, and could compare the new state of `hello` with the
8c7fa247
LT
362state we saved in the index file?
363
914328ac
JH
364Further, remember how I said that `git-write-tree` writes the contents
365of the *index* file to the tree, and thus what we just committed was in
366fact the *original* contents of the file `hello`, not the new ones. We did
8c7fa247 367that on purpose, to show the difference between the index state, and the
2a29da7c 368state in the working tree, and how they don't have to match, even
8c7fa247
LT
369when we commit things.
370
914328ac 371As before, if we do `git-diff-files -p` in our git-tutorial project,
8c7fa247 372we'll still see the same difference we saw last time: the index file
2a29da7c 373hasn't changed by the act of committing anything. However, now that we
8c7fa247 374have committed something, we can also learn to use a new command:
215a7ad1 375`git-diff-index`.
8c7fa247 376
914328ac 377Unlike `git-diff-files`, which showed the difference between the index
215a7ad1 378file and the working tree, `git-diff-index` shows the differences
914328ac 379between a committed *tree* and either the index file or the working
215a7ad1 380tree. In other words, `git-diff-index` wants a tree to be diffed
a7b20909
LT
381against, and before we did the commit, we couldn't do that, because we
382didn't have anything to diff against.
8c7fa247 383
914328ac 384But now we can do
8c7fa247 385
f2416c27
JL
386----------------
387$ git-diff-index -p HEAD
388----------------
8c7fa247 389
914328ac 390(where `-p` has the same meaning as it did in `git-diff-files`), and it
8c7fa247 391will show us the same difference, but for a totally different reason.
2a29da7c
JH
392Now we're comparing the working tree not against the index file,
393but against the tree we just wrote. It just so happens that those two
a7b20909
LT
394are obviously the same, so we get the same result.
395
ed616049
LT
396Again, because this is a common operation, you can also just shorthand
397it with
398
f2416c27
JL
399----------------
400$ git diff HEAD
401----------------
ed616049
LT
402
403which ends up doing the above for you.
404
215a7ad1 405In other words, `git-diff-index` normally compares a tree against the
914328ac 406working tree, but when given the `\--cached` flag, it is told to
a7b20909 407instead compare against just the index cache contents, and ignore the
2a29da7c 408current working tree state entirely. Since we just wrote the index
215a7ad1 409file to HEAD, doing `git-diff-index \--cached -p HEAD` should thus return
a7b20909
LT
410an empty set of differences, and that's exactly what it does.
411
8db9307c 412[NOTE]
914328ac 413================
215a7ad1 414`git-diff-index` really always uses the index for its
8db9307c
JH
415comparisons, and saying that it compares a tree against the working
416tree is thus not strictly accurate. In particular, the list of
914328ac
JH
417files to compare (the "meta-data") *always* comes from the index file,
418regardless of whether the `\--cached` flag is used or not. The `\--cached`
419flag really only determines whether the file *contents* to be compared
8db9307c 420come from the working tree or not.
914328ac 421
8db9307c
JH
422This is not hard to understand, as soon as you realize that git simply
423never knows (or cares) about files that it is not told about
72e9340c 424explicitly. git will never go *looking* for files to compare, it
8db9307c
JH
425expects you to tell it what the files are, and that's what the index
426is there for.
914328ac 427================
8c7fa247 428
914328ac 429However, our next step is to commit the *change* we did, and again, to
837eedf4 430understand what's going on, keep in mind the difference between "working
2a29da7c
JH
431tree contents", "index file" and "committed tree". We have changes
432in the working tree that we want to commit, and we always have to
8c7fa247
LT
433work through the index file, so the first thing we need to do is to
434update the index cache:
435
8db9307c 436------------------------------------------------
f2416c27 437$ git-update-index hello
8db9307c 438------------------------------------------------
8c7fa247 439
914328ac 440(note how we didn't need the `\--add` flag this time, since git knew
8c7fa247
LT
441about the file already).
442
914328ac
JH
443Note what happens to the different `git-diff-\*` versions here. After
444we've updated `hello` in the index, `git-diff-files -p` now shows no
215a7ad1 445differences, but `git-diff-index -p HEAD` still *does* show that the
2a29da7c 446current state is different from the state we committed. In fact, now
215a7ad1 447`git-diff-index` shows the same difference whether we use the `--cached`
2a29da7c 448flag or not, since now the index is coherent with the working tree.
8c7fa247 449
914328ac 450Now, since we've updated `hello` in the index, we can commit the new
2a29da7c 451version. We could do it by writing the tree by hand again, and
914328ac
JH
452committing the tree (this time we'd have to use the `-p HEAD` flag to
453tell commit that the HEAD was the *parent* of the new commit, and that
ed616049
LT
454this wasn't an initial commit any more), but you've done that once
455already, so let's just use the helpful script this time:
8c7fa247 456
8db9307c 457------------------------------------------------
f2416c27 458$ git commit
8db9307c 459------------------------------------------------
8c7fa247 460
ed616049 461which starts an editor for you to write the commit message and tells you
2a29da7c 462a bit about what you have done.
ed616049 463
8c7fa247
LT
464Write whatever message you want, and all the lines that start with '#'
465will be pruned out, and the rest will be used as the commit message for
466the change. If you decide you don't want to commit anything after all at
5f3aa197 467this point (you can continue to edit things and update the index), you
914328ac 468can just leave an empty message. Otherwise `git commit` will commit
8c7fa247
LT
469the change for you.
470
8c7fa247 471You've now made your first real git commit. And if you're interested in
914328ac 472looking at what `git commit` really does, feel free to investigate:
8c7fa247 473it's a few very simple shell scripts to generate the helpful (?) commit
914328ac 474message headers, and a few one-liners that actually do the
215a7ad1 475commit itself (`git-commit`).
8c7fa247
LT
476
477
d154dcc8
JL
478Inspecting Changes
479------------------
8c7fa247
LT
480
481While creating changes is useful, it's even more useful if you can tell
2a29da7c 482later what changed. The most useful command for this is another of the
914328ac 483`diff` family, namely `git-diff-tree`.
8c7fa247 484
914328ac 485`git-diff-tree` can be given two arbitrary trees, and it will tell you the
8c7fa247
LT
486differences between them. Perhaps even more commonly, though, you can
487give it just a single commit object, and it will figure out the parent
488of that commit itself, and show the difference directly. Thus, to get
489the same diff that we've already seen several times, we can now do
490
f2416c27
JL
491----------------
492$ git-diff-tree -p HEAD
493----------------
8c7fa247 494
914328ac
JH
495(again, `-p` means to show the difference as a human-readable patch),
496and it will show what the last commit (in `HEAD`) actually changed.
8c7fa247 497
36f05ef4
JH
498[NOTE]
499============
500Here is an ASCII art by Jon Loeliger that illustrates how
501various diff-\* commands compare things.
502
503 diff-tree
504 +----+
505 | |
506 | |
507 V V
508 +-----------+
509 | Object DB |
510 | Backing |
511 | Store |
512 +-----------+
513 ^ ^
514 | |
515 | | diff-index --cached
516 | |
517 diff-index | V
518 | +-----------+
519 | | Index |
520 | | "cache" |
521 | +-----------+
522 | ^
523 | |
524 | | diff-files
525 | |
526 V V
527 +-----------+
528 | Working |
529 | Directory |
530 +-----------+
531============
532
914328ac 533More interestingly, you can also give `git-diff-tree` the `-v` flag, which
8c7fa247
LT
534tells it to also show the commit message and author and date of the
535commit, and you can tell it to show a whole series of diffs.
536Alternatively, you can tell it to be "silent", and not show the diffs at
537all, but just show the actual commit message.
538
914328ac
JH
539In fact, together with the `git-rev-list` program (which generates a
540list of revisions), `git-diff-tree` ends up being a veritable fount of
541changes. A trivial (but very useful) script called `git-whatchanged` is
8c7fa247 542included with git which does exactly this, and shows a log of recent
2a29da7c 543activities.
8c7fa247 544
81bb573e 545To see the whole history of our pitiful little git-tutorial project, you
8c7fa247
LT
546can do
547
f2416c27
JL
548----------------
549$ git log
550----------------
81bb573e
LT
551
552which shows just the log messages, or if we want to see the log together
cc29f732 553with the associated patches use the more complex (and much more
81bb573e
LT
554powerful)
555
f2416c27
JL
556----------------
557$ git-whatchanged -p --root
558----------------
8c7fa247 559
81bb573e
LT
560and you will see exactly what has changed in the repository over its
561short history.
562
8db9307c 563[NOTE]
914328ac
JH
564The `\--root` flag is a flag to `git-diff-tree` to tell it to
565show the initial aka 'root' commit too. Normally you'd probably not
8db9307c
JH
566want to see the initial import diff, but since the tutorial project
567was started from scratch and is so small, we use it to make the result
568a bit more interesting.
8c7fa247 569
837eedf4 570With that, you should now be having some inkling of what git does, and
8c7fa247
LT
571can explore on your own.
572
8db9307c
JH
573[NOTE]
574Most likely, you are not directly using the core
575git Plumbing commands, but using Porcelain like Cogito on top
576of it. Cogito works a bit differently and you usually do not
215a7ad1 577have to run `git-update-index` yourself for changed files (you
8db9307c 578do tell underlying git about additions and removals via
914328ac
JH
579`cg-add` and `cg-rm` commands). Just before you make a commit
580with `cg-commit`, Cogito figures out which files you modified,
215a7ad1 581and runs `git-update-index` on them for you.
3eb5128a
JH
582
583
2a29da7c
JH
584Tagging a version
585-----------------
3eb5128a 586
2a29da7c 587In git, there are two kinds of tags, a "light" one, and an "annotated tag".
3eb5128a
JH
588
589A "light" tag is technically nothing more than a branch, except we put
914328ac 590it in the `.git/refs/tags/` subdirectory instead of calling it a `head`.
3eb5128a
JH
591So the simplest form of tag involves nothing more than
592
8db9307c 593------------------------------------------------
f2416c27 594$ git tag my-first-tag
8db9307c 595------------------------------------------------
3eb5128a 596
914328ac 597which just writes the current `HEAD` into the `.git/refs/tags/my-first-tag`
a7333f9e 598file, after which point you can then use this symbolic name for that
2a29da7c 599particular state. You can, for example, do
3eb5128a 600
f2416c27
JL
601----------------
602$ git diff my-first-tag
603----------------
3eb5128a
JH
604
605to diff your current state against that tag (which at this point will
606obviously be an empty diff, but if you continue to develop and commit
ade75a59 607stuff, you can use your tag as an "anchor-point" to see what has changed
3eb5128a
JH
608since you tagged it.
609
2a29da7c 610An "annotated tag" is actually a real git object, and contains not only a
3eb5128a 611pointer to the state you want to tag, but also a small tag name and
914328ac
JH
612message, along with optionally a PGP signature that says that yes,
613you really did
614that tag. You create these annotated tags with either the `-a` or
615`-s` flag to `git tag`:
3eb5128a 616
f2416c27
JL
617----------------
618$ git tag -s <tagname>
619----------------
3eb5128a 620
914328ac 621which will sign the current `HEAD` (but you can also give it another
3eb5128a 622argument that specifies the thing to tag, ie you could have tagged the
914328ac 623current `mybranch` point by using `git tag <tagname> mybranch`).
3eb5128a
JH
624
625You normally only do signed tags for major releases or things
626like that, while the light-weight tags are useful for any marking you
914328ac 627want to do -- any time you decide that you want to remember a certain
3eb5128a
JH
628point, just create a private tag for it, and you have a nice symbolic
629name for the state at that point.
630
631
2a29da7c
JH
632Copying repositories
633--------------------
f35ca9ed 634
f2416c27
JL
635git repositories are normally totally self-sufficient and relocatable
636Unlike CVS, for example, there is no separate notion of
914328ac
JH
637"repository" and "working tree". A git repository normally *is* the
638working tree, with the local git information hidden in the `.git`
2a29da7c 639subdirectory. There is nothing else. What you see is what you got.
f35ca9ed 640
8db9307c
JH
641[NOTE]
642You can tell git to split the git internal information from
643the directory that it tracks, but we'll ignore that for now: it's not
644how normal projects work, and it's really only meant for special uses.
645So the mental model of "the git information is always tied directly to
646the working tree that it describes" may not be technically 100%
647accurate, but it's a good model for all normal use.
f35ca9ed
LT
648
649This has two implications:
650
2a29da7c 651 - if you grow bored with the tutorial repository you created (or you've
f35ca9ed 652 made a mistake and want to start all over), you can just do simple
f2416c27
JL
653+
654----------------
655$ rm -rf git-tutorial
656----------------
8db9307c
JH
657+
658and it will be gone. There's no external repository, and there's no
659history outside the project you created.
f35ca9ed 660
2a29da7c 661 - if you want to move or duplicate a git repository, you can do so. There
914328ac 662 is `git clone` command, but if all you want to do is just to
2a29da7c 663 create a copy of your repository (with all the full history that
e7c1ca42 664 went along with it), you can do so with a regular
914328ac 665 `cp -a git-tutorial new-git-tutorial`.
8db9307c
JH
666+
667Note that when you've moved or copied a git repository, your git index
668file (which caches various information, notably some of the "stat"
669information for the files involved) will likely need to be refreshed.
914328ac 670So after you do a `cp -a` to create a new copy, you'll want to do
f2416c27
JL
671+
672----------------
673$ git-update-index --refresh
674----------------
8db9307c
JH
675+
676in the new repository to make sure that the index file is up-to-date.
f35ca9ed 677
2a29da7c 678Note that the second point is true even across machines. You can
914328ac
JH
679duplicate a remote git repository with *any* regular copy mechanism, be it
680`scp`, `rsync` or `wget`.
f35ca9ed
LT
681
682When copying a remote repository, you'll want to at a minimum update the
2a29da7c 683index cache when you do this, and especially with other peoples'
f35ca9ed 684repositories you often want to make sure that the index cache is in some
914328ac 685known state (you don't know *what* they've done and not yet checked in),
215a7ad1 686so usually you'll precede the `git-update-index` with a
f35ca9ed 687
f2416c27
JL
688----------------
689$ git-read-tree --reset HEAD
690$ git-update-index --refresh
691----------------
f35ca9ed 692
914328ac 693which will force a total index re-build from the tree pointed to by `HEAD`.
215a7ad1 694It resets the index contents to `HEAD`, and then the `git-update-index`
2a29da7c
JH
695makes sure to match up all index entries with the checked-out files.
696If the original repository had uncommitted changes in its
215a7ad1 697working tree, `git-update-index --refresh` notices them and
2a29da7c 698tells you they need to be updated.
f35ca9ed 699
ce30a4b6
LT
700The above can also be written as simply
701
f2416c27
JL
702----------------
703$ git reset
704----------------
ce30a4b6
LT
705
706and in fact a lot of the common git command combinations can be scripted
c87d41eb
JL
707with the `git xyz` interfaces. You can learn things by just looking
708at what the various git scripts do. For example, `git reset` is the
709above two lines implemented in `git-reset`, but some things like
710`git status` and `git commit` are slightly more complex scripts around
711the basic git commands.
ce30a4b6 712
2a29da7c 713Many (most?) public remote repositories will not contain any of
914328ac 714the checked out files or even an index file, and will *only* contain the
2a29da7c 715actual core git files. Such a repository usually doesn't even have the
8db9307c 716`.git` subdirectory, but has all the git files directly in the
ce30a4b6 717repository.
f35ca9ed
LT
718
719To create your own local live copy of such a "raw" git repository, you'd
cc29f732 720first create your own subdirectory for the project, and then copy the
914328ac 721raw repository contents into the `.git` directory. For example, to
f35ca9ed
LT
722create your own copy of the git repository, you'd do the following
723
f2416c27
JL
724----------------
725$ mkdir my-git
726$ cd my-git
727$ rsync -rL rsync://rsync.kernel.org/pub/scm/git/git.git/ .git
728----------------
f35ca9ed
LT
729
730followed by
731
f2416c27
JL
732----------------
733$ git-read-tree HEAD
734----------------
f35ca9ed
LT
735
736to populate the index. However, now you have populated the index, and
737you have all the git internal files, but you will notice that you don't
2a29da7c 738actually have any of the working tree files to work on. To get
f35ca9ed
LT
739those, you'd check them out with
740
f2416c27
JL
741----------------
742$ git-checkout-index -u -a
743----------------
f35ca9ed 744
914328ac 745where the `-u` flag means that you want the checkout to keep the index
cc29f732 746up-to-date (so that you don't have to refresh it afterward), and the
914328ac
JH
747`-a` flag means "check out all files" (if you have a stale copy or an
748older version of a checked out tree you may also need to add the `-f`
215a7ad1 749flag first, to tell git-checkout-index to *force* overwriting of any old
f35ca9ed
LT
750files).
751
ed616049
LT
752Again, this can all be simplified with
753
f2416c27
JL
754----------------
755$ git clone rsync://rsync.kernel.org/pub/scm/git/git.git/ my-git
756$ cd my-git
757$ git checkout
758----------------
ed616049
LT
759
760which will end up doing all of the above for you.
761
cc29f732 762You have now successfully copied somebody else's (mine) remote
f35ca9ed
LT
763repository, and checked it out.
764
ed616049 765
2a29da7c
JH
766Creating a new branch
767---------------------
ed616049
LT
768
769Branches in git are really nothing more than pointers into the git
914328ac
JH
770object database from within the `.git/refs/` subdirectory, and as we
771already discussed, the `HEAD` branch is nothing but a symlink to one of
ed616049
LT
772these object pointers.
773
774You can at any time create a new branch by just picking an arbitrary
775point in the project history, and just writing the SHA1 name of that
914328ac 776object into a file under `.git/refs/heads/`. You can use any filename you
ed616049 777want (and indeed, subdirectories), but the convention is that the
914328ac 778"normal" branch is called `master`. That's just a convention, though,
ed616049
LT
779and nothing enforces it.
780
2a29da7c 781To show that as an example, let's go back to the git-tutorial repository we
a7333f9e
LT
782used earlier, and create a branch in it. You do that by simply just
783saying that you want to check out a new branch:
ed616049 784
8db9307c 785------------
f2416c27 786$ git checkout -b mybranch
8db9307c 787------------
ed616049 788
914328ac 789will create a new branch based at the current `HEAD` position, and switch
a7333f9e 790to it.
ed616049 791
8db9307c
JH
792[NOTE]
793================================================
794If you make the decision to start your new branch at some
914328ac
JH
795other point in the history than the current `HEAD`, you can do so by
796just telling `git checkout` what the base of the checkout would be.
8db9307c 797In other words, if you have an earlier tag or branch, you'd just do
ed616049 798
2ae6c706 799------------
f2416c27 800$ git checkout -b mybranch earlier-commit
2ae6c706 801------------
ed616049 802
914328ac 803and it would create the new branch `mybranch` at the earlier commit,
8db9307c
JH
804and check out the state at that time.
805================================================
ed616049 806
914328ac 807You can always just jump back to your original `master` branch by doing
ed616049 808
2ae6c706 809------------
f2416c27 810$ git checkout master
2ae6c706 811------------
ed616049 812
a7333f9e
LT
813(or any other branch-name, for that matter) and if you forget which
814branch you happen to be on, a simple
ed616049 815
2ae6c706 816------------
f2416c27 817$ ls -l .git/HEAD
2ae6c706 818------------
ed616049 819
2ae6c706
JS
820will tell you where it's pointing (Note that on platforms with bad or no
821symlink support, you have to execute
ed616049 822
2ae6c706 823------------
f2416c27 824$ cat .git/HEAD
2ae6c706
JS
825------------
826
827instead). To get the list of branches you have, you can say
828
829------------
f2416c27 830$ git branch
2ae6c706 831------------
2a29da7c 832
8db9307c 833which is nothing more than a simple script around `ls .git/refs/heads`.
928f74de 834There will be asterisk in front of the branch you are currently on.
2a29da7c
JH
835
836Sometimes you may wish to create a new branch _without_ actually
a7333f9e
LT
837checking it out and switching to it. If so, just use the command
838
2ae6c706 839------------
f2416c27 840$ git branch <branchname> [startingpoint]
2ae6c706 841------------
a7333f9e
LT
842
843which will simply _create_ the branch, but will not do anything further.
914328ac
JH
844You can then later -- once you decide that you want to actually develop
845on that branch -- switch to that branch with a regular `git checkout`
a7333f9e
LT
846with the branchname as the argument.
847
ed616049 848
2a29da7c
JH
849Merging two branches
850--------------------
ed616049
LT
851
852One of the ideas of having a branch is that you do some (possibly
853experimental) work in it, and eventually merge it back to the main
914328ac
JH
854branch. So assuming you created the above `mybranch` that started out
855being the same as the original `master` branch, let's make sure we're in
ed616049
LT
856that branch, and do some work there.
857
914328ac 858------------------------------------------------
f2416c27
JL
859$ git checkout mybranch
860$ echo "Work, work, work" >>hello
861$ git commit -m 'Some work.' hello
914328ac 862------------------------------------------------
ed616049 863
914328ac 864Here, we just added another line to `hello`, and we used a shorthand for
96768e31 865doing both `git-update-index hello` and `git commit` by just giving the
914328ac 866filename directly to `git commit`. The `-m` flag is to give the
2a29da7c 867commit log message from the command line.
ed616049
LT
868
869Now, to make it a bit more interesting, let's assume that somebody else
870does some work in the original branch, and simulate that by going back
871to the master branch, and editing the same file differently there:
872
8db9307c 873------------
f2416c27 874$ git checkout master
8db9307c 875------------
ed616049 876
914328ac
JH
877Here, take a moment to look at the contents of `hello`, and notice how they
878don't contain the work we just did in `mybranch` -- because that work
879hasn't happened in the `master` branch at all. Then do
ed616049 880
8db9307c 881------------
f2416c27
JL
882$ echo "Play, play, play" >>hello
883$ echo "Lots of fun" >>example
884$ git commit -m 'Some fun.' hello example
8db9307c 885------------
ed616049
LT
886
887since the master branch is obviously in a much better mood.
888
889Now, you've got two branches, and you decide that you want to merge the
890work done. Before we do that, let's introduce a cool graphical tool that
891helps you view what's going on:
892
f2416c27
JL
893----------------
894$ gitk --all
895----------------
ed616049 896
914328ac
JH
897will show you graphically both of your branches (that's what the `\--all`
898means: normally it will just show you your current `HEAD`) and their
2a29da7c 899histories. You can also see exactly how they came to be from a common
ed616049
LT
900source.
901
914328ac
JH
902Anyway, let's exit `gitk` (`^Q` or the File menu), and decide that we want
903to merge the work we did on the `mybranch` branch into the `master`
904branch (which is currently our `HEAD` too). To do that, there's a nice
44760f1d 905script called `git merge`, which wants to know which branches you want
ed616049
LT
906to resolve and what the merge is all about:
907
8db9307c 908------------
f2416c27 909$ git merge "Merge work in mybranch" HEAD mybranch
8db9307c 910------------
ed616049 911
44760f1d 912where the first argument is going to be used as the commit message if
ed616049
LT
913the merge can be resolved automatically.
914
915Now, in this case we've intentionally created a situation where the
916merge will need to be fixed up by hand, though, so git will do as much
914328ac
JH
917of it as it can automatically (which in this case is just merge the `example`
918file, which had no differences in the `mybranch` branch), and say:
ed616049 919
f2416c27 920----------------
44760f1d
JH
921 Trying really trivial in-index merge...
922 fatal: Merge requires file-level merging
923 Nope.
924 ...
0501c240
JH
925 Auto-merging hello
926 CONFLICT (content): Merge conflict in hello
44760f1d 927 Automatic merge failed/prevented; fix up by hand
f2416c27 928----------------
ed616049
LT
929
930which is way too verbose, but it basically tells you that it failed the
931really trivial merge ("Simple merge") and did an "Automatic merge"
914328ac 932instead, but that too failed due to conflicts in `hello`.
ed616049 933
914328ac 934Not to worry. It left the (trivial) conflict in `hello` in the same form you
ed616049 935should already be well used to if you've ever used CVS, so let's just
914328ac
JH
936open `hello` in our editor (whatever that may be), and fix it up somehow.
937I'd suggest just making it so that `hello` contains all four lines:
ed616049 938
8db9307c
JH
939------------
940Hello World
941It's a new day for git
942Play, play, play
943Work, work, work
944------------
ed616049
LT
945
946and once you're happy with your manual merge, just do a
947
8db9307c 948------------
f2416c27 949$ git commit hello
8db9307c 950------------
ed616049
LT
951
952which will very loudly warn you that you're now committing a merge
953(which is correct, so never mind), and you can write a small merge
914328ac 954message about your adventures in git-merge-land.
ed616049 955
e1ccf53a 956After you're done, start up `gitk \--all` to see graphically what the
914328ac 957history looks like. Notice that `mybranch` still exists, and you can
2a29da7c 958switch to it, and continue to work with it if you want to. The
914328ac
JH
959`mybranch` branch will not contain the merge, but next time you merge it
960from the `master` branch, git will know how you merged it, so you'll not
ed616049
LT
961have to do _that_ merge again.
962
8db9307c 963Another useful tool, especially if you do not always work in X-Window
914328ac 964environment, is `git show-branch`.
2a29da7c
JH
965
966------------------------------------------------
967$ git show-branch master mybranch
0501c240 968* [master] Merge work in mybranch
2a29da7c
JH
969 ! [mybranch] Some work.
970--
0501c240 971+ [master] Merge work in mybranch
2a29da7c
JH
972++ [mybranch] Some work.
973------------------------------------------------
974
975The first two lines indicate that it is showing the two branches
976and the first line of the commit log message from their
914328ac
JH
977top-of-the-tree commits, you are currently on `master` branch
978(notice the asterisk `*` character), and the first column for
2a29da7c 979the later output lines is used to show commits contained in the
914328ac 980`master` branch, and the second column for the `mybranch`
2a29da7c 981branch. Three commits are shown along with their log messages.
914328ac
JH
982All of them have plus `+` characters in the first column, which
983means they are now part of the `master` branch. Only the "Some
984work" commit has the plus `+` character in the second column,
985because `mybranch` has not been merged to incorporate these
6f60300b
JH
986commits from the master branch. The string inside brackets
987before the commit log message is a short name you can use to
988name the commit. In the above example, 'master' and 'mybranch'
989are branch heads. 'master~1' is the first parent of 'master'
990branch head. Please see 'git-rev-parse' documentation if you
991see more complex cases.
2a29da7c
JH
992
993Now, let's pretend you are the one who did all the work in
914328ac
JH
994`mybranch`, and the fruit of your hard work has finally been merged
995to the `master` branch. Let's go back to `mybranch`, and run
2a29da7c
JH
996resolve to get the "upstream changes" back to your branch.
997
2ae6c706 998------------
f2416c27
JL
999$ git checkout mybranch
1000$ git merge "Merge upstream changes." HEAD master
2ae6c706 1001------------
2a29da7c
JH
1002
1003This outputs something like this (the actual commit object names
1004would be different)
1005
f2416c27
JL
1006----------------
1007Updating from ae3a2da... to a80b4aa....
1008 example | 1 +
1009 hello | 1 +
1010 2 files changed, 2 insertions(+), 0 deletions(-)
1011----------------
2a29da7c
JH
1012
1013Because your branch did not contain anything more than what are
914328ac 1014already merged into the `master` branch, the resolve operation did
2a29da7c 1015not actually do a merge. Instead, it just updated the top of
914328ac
JH
1016the tree of your branch to that of the `master` branch. This is
1017often called 'fast forward' merge.
ed616049 1018
e1ccf53a 1019You can run `gitk \--all` again to see how the commit ancestry
914328ac 1020looks like, or run `show-branch`, which tells you this.
2a29da7c
JH
1021
1022------------------------------------------------
1023$ git show-branch master mybranch
0501c240
JH
1024! [master] Merge work in mybranch
1025 * [mybranch] Merge work in mybranch
2a29da7c 1026--
0501c240 1027++ [master] Merge work in mybranch
2a29da7c
JH
1028------------------------------------------------
1029
1030
1031Merging external work
1032---------------------
ed616049
LT
1033
1034It's usually much more common that you merge with somebody else than
1035merging with your own branches, so it's worth pointing out that git
1036makes that very easy too, and in fact, it's not that different from
067744bd 1037doing a `git merge`. In fact, a remote merge ends up being nothing
ed616049 1038more than "fetch the work from a remote repository into a temporary tag"
067744bd 1039followed by a `git merge`.
ed616049 1040
914328ac
JH
1041Fetching from a remote repository is done by, unsurprisingly,
1042`git fetch`:
ed616049 1043
f2416c27
JL
1044----------------
1045$ git fetch <remote-repository>
1046----------------
ed616049 1047
914328ac
JH
1048One of the following transports can be used to name the
1049repository to download from:
ed616049 1050
914328ac
JH
1051Rsync::
1052 `rsync://remote.machine/path/to/repo.git/`
1053+
1054Rsync transport is usable for both uploading and downloading,
1055but is completely unaware of what git does, and can produce
1056unexpected results when you download from the public repository
1057while the repository owner is uploading into it via `rsync`
1058transport. Most notably, it could update the files under
1059`refs/` which holds the object name of the topmost commits
1060before uploading the files in `objects/` -- the downloader would
1061obtain head commit object name while that object itself is still
1062not available in the repository. For this reason, it is
1063considered deprecated.
1064
1065SSH::
1066 `remote.machine:/path/to/repo.git/` or
1067+
1068`ssh://remote.machine/path/to/repo.git/`
1069+
1070This transport can be used for both uploading and downloading,
1071and requires you to have a log-in privilege over `ssh` to the
1072remote machine. It finds out the set of objects the other side
1073lacks by exchanging the head commits both ends have and
1074transfers (close to) minimum set of objects. It is by far the
1075most efficient way to exchange git objects between repositories.
1076
1077Local directory::
1078 `/path/to/repo.git/`
1079+
1080This transport is the same as SSH transport but uses `sh` to run
1081both ends on the local machine instead of running other end on
1082the remote machine via `ssh`.
ed616049 1083
72e9340c 1084git Native::
914328ac
JH
1085 `git://remote.machine/path/to/repo.git/`
1086+
1087This transport was designed for anonymous downloading. Like SSH
1088transport, it finds out the set of objects the downstream side
1089lacks and transfers (close to) minimum set of objects.
ed616049 1090
f2416c27 1091HTTP(S)::
914328ac
JH
1092 `http://remote.machine/path/to/repo.git/`
1093+
80248b2e
JH
1094Downloader from http and https URL
1095first obtains the topmost commit object name from the remote site
1096by looking at the specified refname under `repo.git/refs/` directory,
1097and then tries to obtain the
914328ac
JH
1098commit object by downloading from `repo.git/objects/xx/xxx\...`
1099using the object name of that commit object. Then it reads the
1100commit object to find out its parent commits and the associate
1101tree object; it repeats this process until it gets all the
1102necessary objects. Because of this behaviour, they are
1103sometimes also called 'commit walkers'.
1104+
1105The 'commit walkers' are sometimes also called 'dumb
72e9340c
CM
1106transports', because they do not require any git aware smart
1107server like git Native transport does. Any stock HTTP server
80248b2e
JH
1108that does not even support directory index would suffice. But
1109you must prepare your repository with `git-update-server-info`
1110to help dumb transport downloaders.
914328ac 1111+
215a7ad1 1112There are (confusingly enough) `git-ssh-fetch` and `git-ssh-upload`
914328ac 1113programs, which are 'commit walkers'; they outlived their
72e9340c 1114usefulness when git Native and SSH transports were introduced,
914328ac 1115and not used by `git pull` or `git push` scripts.
ed616049 1116
914328ac
JH
1117Once you fetch from the remote repository, you `resolve` that
1118with your current branch.
ade75a59 1119
914328ac
JH
1120However -- it's such a common thing to `fetch` and then
1121immediately `resolve`, that it's called `git pull`, and you can
1122simply do
ed616049 1123
f2416c27
JL
1124----------------
1125$ git pull <remote-repository>
1126----------------
914328ac
JH
1127
1128and optionally give a branch-name for the remote end as a second
1129argument.
ed616049 1130
8db9307c
JH
1131[NOTE]
1132You could do without using any branches at all, by
1133keeping as many local repositories as you would like to have
914328ac 1134branches, and merging between them with `git pull`, just like
8db9307c 1135you merge between branches. The advantage of this approach is
914328ac 1136that it lets you keep set of files for each `branch` checked
8db9307c
JH
1137out and you may find it easier to switch back and forth if you
1138juggle multiple lines of development simultaneously. Of
1139course, you will pay the price of more disk usage to hold
1140multiple working trees, but disk space is cheap these days.
1141
1142[NOTE]
1143You could even pull from your own repository by
710c97db
JH
1144giving '.' as <remote-repository> parameter to `git pull`. This
1145is useful when you want to merge a local branch (or more, if you
1146are making an Octopus) into the current branch.
ed616049 1147
0c04094b 1148It is likely that you will be pulling from the same remote
2a29da7c 1149repository from time to time. As a short hand, you can store
c9517341 1150the remote repository URL in a file under .git/remotes/
0c04094b
JH
1151directory, like this:
1152
c9517341 1153------------------------------------------------
f2416c27
JL
1154$ mkdir -p .git/remotes/
1155$ cat >.git/remotes/linus <<\EOF
c9517341
JH
1156URL: http://www.kernel.org/pub/scm/git/git.git/
1157EOF
1158------------------------------------------------
0c04094b 1159
914328ac 1160and use the filename to `git pull` instead of the full URL.
c9517341 1161The URL specified in such file can even be a prefix
0c04094b
JH
1162of a full URL, like this:
1163
c9517341 1164------------------------------------------------
f2416c27 1165$ cat >.git/remotes/jgarzik <<\EOF
c9517341
JH
1166URL: http://www.kernel.org/pub/scm/linux/git/jgarzik/
1167EOF
1168------------------------------------------------
1169
0c04094b
JH
1170
1171Examples.
1172
914328ac
JH
1173. `git pull linus`
1174. `git pull linus tag v0.99.1`
1175. `git pull jgarzik/netdev-2.6.git/ e100`
0c04094b
JH
1176
1177the above are equivalent to:
1178
914328ac
JH
1179. `git pull http://www.kernel.org/pub/scm/git/git.git/ HEAD`
1180. `git pull http://www.kernel.org/pub/scm/git/git.git/ tag v0.99.1`
1181. `git pull http://www.kernel.org/pub/.../jgarzik/netdev-2.6.git e100`
0c04094b 1182
e7c1ca42 1183
44760f1d
JH
1184How does the merge work?
1185------------------------
1186
1187We said this tutorial shows what plumbing does to help you cope
1188with the porcelain that isn't flushing, but we so far did not
1189talk about how the merge really works. If you are following
1190this tutorial the first time, I'd suggest to skip to "Publishing
1191your work" section and come back here later.
1192
1193OK, still with me? To give us an example to look at, let's go
1194back to the earlier repository with "hello" and "example" file,
1195and bring ourselves back to the pre-merge state:
1196
1197------------
1198$ git show-branch --more=3 master mybranch
1199! [master] Merge work in mybranch
1200 * [mybranch] Merge work in mybranch
1201--
1202++ [master] Merge work in mybranch
1203++ [master^2] Some work.
1204++ [master^] Some fun.
1205------------
1206
1207Remember, before running `git merge`, our `master` head was at
1208"Some fun." commit, while our `mybranch` head was at "Some
1209work." commit.
1210
1211------------
1212$ git checkout mybranch
1213$ git reset --hard master^2
1214$ git checkout master
1215$ git reset --hard master^
1216------------
1217
1218After rewinding, the commit structure should look like this:
1219
1220------------
1221$ git show-branch
1222* [master] Some fun.
1223 ! [mybranch] Some work.
1224--
1225 + [mybranch] Some work.
1226+ [master] Some fun.
1227++ [mybranch^] New day.
1228------------
1229
1230Now we are ready to experiment with the merge by hand.
1231
1232`git merge` command, when merging two branches, uses 3-way merge
1233algorithm. First, it finds the common ancestor between them.
1234The command it uses is `git-merge-base`:
1235
1236------------
1237$ mb=$(git-merge-base HEAD mybranch)
1238------------
1239
1240The command writes the commit object name of the common ancestor
1241to the standard output, so we captured its output to a variable,
1242because we will be using it in the next step. BTW, the common
1243ancestor commit is the "New day." commit in this case. You can
1244tell it by:
1245
1246------------
1247$ git-name-rev $mb
1248my-first-tag
1249------------
1250
1251After finding out a common ancestor commit, the second step is
1252this:
1253
1254------------
1255$ git-read-tree -m -u $mb HEAD mybranch
1256------------
1257
1258This is the same `git-read-tree` command we have already seen,
1259but it takes three trees, unlike previous examples. This reads
1260the contents of each tree into different 'stage' in the index
1261file (the first tree goes to stage 1, the second stage 2,
1262etc.). After reading three trees into three stages, the paths
1263that are the same in all three stages are 'collapsed' into stage
12640. Also paths that are the same in two of three stages are
1265collapsed into stage 0, taking the SHA1 from either stage 2 or
1266stage 3, whichever is different from stage 1 (i.e. only one side
1267changed from the common ancestor).
1268
1269After 'collapsing' operation, paths that are different in three
1270trees are left in non-zero stages. At this point, you can
1271inspect the index file with this command:
1272
1273------------
1274$ git-ls-files --stage
1275100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example
1276100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello
1277100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello
1278100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello
1279------------
1280
1281In our example of only two files, we did not have unchanged
1282files so only 'example' resulted in collapsing, but in real-life
1283large projects, only small number of files change in one commit,
1284and this 'collapsing' tends to trivially merge most of the paths
067744bd
JH
1285fairly quickly, leaving only a handful the real changes in non-zero
1286stages.
44760f1d
JH
1287
1288To look at only non-zero stages, use `\--unmerged` flag:
1289
1290------------
1291$ git-ls-files --unmerged
1292100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello
1293100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello
1294100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello
1295------------
1296
1297The next step of merging is to merge these three versions of the
1298file, using 3-way merge. This is done by giving
1299`git-merge-one-file` command as one of the arguments to
1300`git-merge-index` command:
1301
1302------------
1303$ git-merge-index git-merge-one-file hello
1304Auto-merging hello.
1305merge: warning: conflicts during merge
1306ERROR: Merge conflict in hello.
1307fatal: merge program failed
1308------------
1309
1310`git-merge-one-file` script is called with parameters to
1311describe those three versions, and is responsible to leave the
361c06d8
JH
1312merge results in the working tree.
1313It is a fairly straightforward shell script, and
1314eventually calls `merge` program from RCS suite to perform a
44760f1d
JH
1315file-level 3-way merge. In this case, `merge` detects
1316conflicts, and the merge result with conflict marks is left in
361c06d8 1317the working tree.. This can be seen if you run `ls-files
44760f1d
JH
1318--stage` again at this point:
1319
1320------------
1321$ git-ls-files --stage
1322100644 7f8b141b65fdcee47321e399a2598a235a032422 0 example
361c06d8
JH
1323100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello
1324100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello
1325100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello
44760f1d
JH
1326------------
1327
44760f1d
JH
1328This is the state of the index file and the working file after
1329`git merge` returns control back to you, leaving the conflicting
361c06d8
JH
1330merge for you to resolve. Notice that the path `hello` is still
1331unmerged, and what you see with `git diff` at this point is
1332differences since stage 2 (i.e. your version).
44760f1d
JH
1333
1334
2a29da7c
JH
1335Publishing your work
1336--------------------
e7c1ca42 1337
3eb5128a 1338So we can use somebody else's work from a remote repository; but
914328ac 1339how can *you* prepare a repository to let other people pull from
3eb5128a 1340it?
e7c1ca42 1341
2a29da7c 1342Your do your real work in your working tree that has your
914328ac
JH
1343primary repository hanging under it as its `.git` subdirectory.
1344You *could* make that repository accessible remotely and ask
3eb5128a 1345people to pull from it, but in practice that is not the way
2a29da7c 1346things are usually done. A recommended way is to have a public
3eb5128a 1347repository, make it reachable by other people, and when the
2a29da7c
JH
1348changes you made in your primary working tree are in good shape,
1349update the public repository from it. This is often called
914328ac 1350'pushing'.
e7c1ca42 1351
8db9307c 1352[NOTE]
914328ac
JH
1353This public repository could further be mirrored, and that is
1354how git repositories at `kernel.org` are managed.
e7c1ca42 1355
3eb5128a
JH
1356Publishing the changes from your local (private) repository to
1357your remote (public) repository requires a write privilege on
2a29da7c 1358the remote machine. You need to have an SSH account there to
914328ac 1359run a single command, `git-receive-pack`.
e7c1ca42 1360
3eb5128a 1361First, you need to create an empty repository on the remote
2a29da7c 1362machine that will house your public repository. This empty
3eb5128a 1363repository will be populated and be kept up-to-date by pushing
2a29da7c 1364into it later. Obviously, this repository creation needs to be
e7c1ca42
JH
1365done only once.
1366
8db9307c 1367[NOTE]
914328ac
JH
1368`git push` uses a pair of programs,
1369`git-send-pack` on your local machine, and `git-receive-pack`
8db9307c
JH
1370on the remote machine. The communication between the two over
1371the network internally uses an SSH connection.
3eb5128a 1372
72e9340c 1373Your private repository's git directory is usually `.git`, but
3eb5128a 1374your public repository is often named after the project name,
914328ac
JH
1375i.e. `<project>.git`. Let's create such a public repository for
1376project `my-git`. After logging into the remote machine, create
3eb5128a 1377an empty directory:
e7c1ca42 1378
2ae6c706 1379------------
f2416c27 1380$ mkdir my-git.git
2ae6c706 1381------------
e7c1ca42 1382
72e9340c 1383Then, make that directory into a git repository by running
914328ac
JH
1384`git init-db`, but this time, since its name is not the usual
1385`.git`, we do things slightly differently:
e7c1ca42 1386
2ae6c706 1387------------
f2416c27 1388$ GIT_DIR=my-git.git git-init-db
2ae6c706 1389------------
e7c1ca42
JH
1390
1391Make sure this directory is available for others you want your
2a29da7c 1392changes to be pulled by via the transport of your choice. Also
914328ac
JH
1393you need to make sure that you have the `git-receive-pack`
1394program on the `$PATH`.
3eb5128a 1395
8db9307c 1396[NOTE]
914328ac
JH
1397Many installations of sshd do not invoke your shell as the login
1398shell when you directly run programs; what this means is that if
1399your login shell is `bash`, only `.bashrc` is read and not
1400`.bash_profile`. As a workaround, make sure `.bashrc` sets up
1401`$PATH` so that you can run `git-receive-pack` program.
3eb5128a 1402
953e5842
JH
1403[NOTE]
1404If you plan to publish this repository to be accessed over http,
1405you should do `chmod +x my-git.git/hooks/post-update` at this
1406point. This makes sure that every time you push into this
1407repository, `git-update-server-info` is run.
1408
3eb5128a 1409Your "public repository" is now ready to accept your changes.
2a29da7c 1410Come back to the machine you have your private repository. From
e7c1ca42
JH
1411there, run this command:
1412
2ae6c706 1413------------
f2416c27 1414$ git push <public-host>:/path/to/my-git.git master
2ae6c706 1415------------
e7c1ca42
JH
1416
1417This synchronizes your public repository to match the named
914328ac 1418branch head (i.e. `master` in this case) and objects reachable
3eb5128a 1419from them in your current repository.
e7c1ca42
JH
1420
1421As a real example, this is how I update my public git
2a29da7c 1422repository. Kernel.org mirror network takes care of the
3eb5128a 1423propagation to other publicly visible machines:
e7c1ca42 1424
2ae6c706 1425------------
f2416c27 1426$ git push master.kernel.org:/pub/scm/git/git.git/
2ae6c706 1427------------
e7c1ca42
JH
1428
1429
2a29da7c
JH
1430Packing your repository
1431-----------------------
3eb5128a 1432
914328ac 1433Earlier, we saw that one file under `.git/objects/??/` directory
2a29da7c 1434is stored for each git object you create. This representation
914328ac 1435is efficient to create atomically and safely, but
2a29da7c 1436not so convenient to transport over the network. Since git objects are
3eb5128a 1437immutable once they are created, there is a way to optimize the
2a29da7c 1438storage by "packing them together". The command
3eb5128a 1439
2ae6c706 1440------------
f2416c27 1441$ git repack
2ae6c706 1442------------
3eb5128a 1443
2a29da7c 1444will do it for you. If you followed the tutorial examples, you
914328ac
JH
1445would have accumulated about 17 objects in `.git/objects/??/`
1446directories by now. `git repack` tells you how many objects it
1447packed, and stores the packed file in `.git/objects/pack`
3eb5128a
JH
1448directory.
1449
8db9307c 1450[NOTE]
914328ac
JH
1451You will see two files, `pack-\*.pack` and `pack-\*.idx`,
1452in `.git/objects/pack` directory. They are closely related to
8db9307c
JH
1453each other, and if you ever copy them by hand to a different
1454repository for whatever reason, you should make sure you copy
1455them together. The former holds all the data from the objects
1456in the pack, and the latter holds the index for random
1457access.
3eb5128a 1458
914328ac 1459If you are paranoid, running `git-verify-pack` command would
3eb5128a
JH
1460detect if you have a corrupt pack, but do not worry too much.
1461Our programs are always perfect ;-).
1462
1463Once you have packed objects, you do not need to leave the
1464unpacked objects that are contained in the pack file anymore.
1465
2ae6c706 1466------------
f2416c27 1467$ git prune-packed
2ae6c706 1468------------
3eb5128a
JH
1469
1470would remove them for you.
1471
914328ac
JH
1472You can try running `find .git/objects -type f` before and after
1473you run `git prune-packed` if you are curious. Also `git
1474count-objects` would tell you how many unpacked objects are in
1475your repository and how much space they are consuming.
3eb5128a 1476
8db9307c 1477[NOTE]
914328ac
JH
1478`git pull` is slightly cumbersome for HTTP transport, as a
1479packed repository may contain relatively few objects in a
8db9307c
JH
1480relatively large pack. If you expect many HTTP pulls from your
1481public repository you might want to repack & prune often, or
1482never.
3eb5128a 1483
914328ac 1484If you run `git repack` again at this point, it will say
2a29da7c 1485"Nothing to pack". Once you continue your development and
914328ac 1486accumulate the changes, running `git repack` again will create a
3eb5128a 1487new pack, that contains objects created since you packed your
2a29da7c 1488repository the last time. We recommend that you pack your project
3eb5128a 1489soon after the initial import (unless you are starting your
914328ac 1490project from scratch), and then run `git repack` every once in a
3eb5128a
JH
1491while, depending on how active your project is.
1492
914328ac 1493When a repository is synchronized via `git push` and `git pull`
ade75a59 1494objects packed in the source repository are usually stored
3eb5128a 1495unpacked in the destination, unless rsync transport is used.
914328ac
JH
1496While this allows you to use different packing strategies on
1497both ends, it also means you may need to repack both
1498repositories every once in a while.
3eb5128a
JH
1499
1500
2a29da7c
JH
1501Working with Others
1502-------------------
3eb5128a 1503
a232a132
JH
1504Although git is a truly distributed system, it is often
1505convenient to organize your project with an informal hierarchy
2a29da7c 1506of developers. Linux kernel development is run this way. There
a232a132 1507is a nice illustration (page 17, "Merges to Mainline") in Randy
914328ac 1508Dunlap's presentation (`http://tinyurl.com/a2jdg`).
a232a132 1509
914328ac 1510It should be stressed that this hierarchy is purely *informal*.
a232a132 1511There is nothing fundamental in git that enforces the "chain of
2a29da7c 1512patch flow" this hierarchy implies. You do not have to pull
a232a132
JH
1513from only one remote repository.
1514
a232a132 1515A recommended workflow for a "project lead" goes like this:
3eb5128a 1516
8db9307c
JH
15171. Prepare your primary repository on your local machine. Your
1518 work is done there.
3eb5128a 1519
8db9307c 15202. Prepare a public repository accessible to others.
914328ac
JH
1521+
1522If other people are pulling from your repository over dumb
80248b2e
JH
1523transport protocols (HTTP), you need to keep this repository
1524'dumb transport friendly'. After `git init-db`,
914328ac
JH
1525`$GIT_DIR/hooks/post-update` copied from the standard templates
1526would contain a call to `git-update-server-info` but the
1527`post-update` hook itself is disabled by default -- enable it
80248b2e
JH
1528with `chmod +x post-update`. This makes sure `git-update-server-info`
1529keeps the necessary files up-to-date.
3eb5128a 1530
8db9307c
JH
15313. Push into the public repository from your primary
1532 repository.
3eb5128a 1533
914328ac 15344. `git repack` the public repository. This establishes a big
8db9307c 1535 pack that contains the initial set of objects as the
914328ac 1536 baseline, and possibly `git prune` if the transport
8db9307c
JH
1537 used for pulling from your repository supports packed
1538 repositories.
3eb5128a 1539
8db9307c
JH
15405. Keep working in your primary repository. Your changes
1541 include modifications of your own, patches you receive via
1542 e-mails, and merges resulting from pulling the "public"
1543 repositories of your "subsystem maintainers".
1544+
1545You can repack this private repository whenever you feel like.
3eb5128a 1546
8db9307c
JH
15476. Push your changes to the public repository, and announce it
1548 to the public.
3eb5128a 1549
8db9307c
JH
15507. Every once in a while, "git repack" the public repository.
1551 Go back to step 5. and continue working.
3eb5128a 1552
a232a132 1553
ade75a59
JS
1554A recommended work cycle for a "subsystem maintainer" who works
1555on that project and has an own "public repository" goes like this:
3eb5128a 1556
914328ac 15571. Prepare your work repository, by `git clone` the public
8db9307c 1558 repository of the "project lead". The URL used for the
914328ac 1559 initial cloning is stored in `.git/remotes/origin`.
3eb5128a 1560
914328ac
JH
15612. Prepare a public repository accessible to others, just like
1562 the "project lead" person does.
3eb5128a 1563
8db9307c 15643. Copy over the packed files from "project lead" public
aa7f412a
JH
1565 repository to your public repository, unless the "project
1566 lead" repository lives on the same machine as yours. In the
1567 latter case, you can use `objects/info/alternates` file to
1568 point at the repository you are borrowing from.
3eb5128a 1569
8db9307c 15704. Push into the public repository from your primary
914328ac
JH
1571 repository. Run `git repack`, and possibly `git prune` if the
1572 transport used for pulling from your repository supports
1573 packed repositories.
3eb5128a 1574
8db9307c
JH
15755. Keep working in your primary repository. Your changes
1576 include modifications of your own, patches you receive via
1577 e-mails, and merges resulting from pulling the "public"
1578 repositories of your "project lead" and possibly your
1579 "sub-subsystem maintainers".
1580+
1581You can repack this private repository whenever you feel
1582like.
3eb5128a 1583
8db9307c
JH
15846. Push your changes to your public repository, and ask your
1585 "project lead" and possibly your "sub-subsystem
1586 maintainers" to pull from it.
a232a132 1587
914328ac 15887. Every once in a while, `git repack` the public repository.
8db9307c 1589 Go back to step 5. and continue working.
3eb5128a 1590
a232a132 1591
3eb5128a 1592A recommended work cycle for an "individual developer" who does
2a29da7c 1593not have a "public" repository is somewhat different. It goes
3eb5128a
JH
1594like this:
1595
914328ac 15961. Prepare your work repository, by `git clone` the public
8db9307c
JH
1597 repository of the "project lead" (or a "subsystem
1598 maintainer", if you work on a subsystem). The URL used for
914328ac 1599 the initial cloning is stored in `.git/remotes/origin`.
3eb5128a 1600
914328ac 16012. Do your work in your repository on 'master' branch.
3eb5128a 1602
914328ac 16033. Run `git fetch origin` from the public repository of your
8db9307c 1604 upstream every once in a while. This does only the first
914328ac
JH
1605 half of `git pull` but does not merge. The head of the
1606 public repository is stored in `.git/refs/heads/origin`.
3eb5128a 1607
914328ac
JH
16084. Use `git cherry origin` to see which ones of your patches
1609 were accepted, and/or use `git rebase origin` to port your
8db9307c 1610 unmerged changes forward to the updated upstream.
3eb5128a 1611
914328ac 16125. Use `git format-patch origin` to prepare patches for e-mail
8db9307c 1613 submission to your upstream and send it out. Go back to
914328ac 1614 step 2. and continue.
3eb5128a
JH
1615
1616
2a29da7c
JH
1617Working with Others, Shared Repository Style
1618--------------------------------------------
1619
1620If you are coming from CVS background, the style of cooperation
1621suggested in the previous section may be new to you. You do not
1622have to worry. git supports "shared public repository" style of
c9517341
JH
1623cooperation you are probably more familiar with as well.
1624
1625For this, set up a public repository on a machine that is
1626reachable via SSH by people with "commit privileges". Put the
1627committers in the same user group and make the repository
1628writable by that group.
1629
914328ac 1630You, as an individual committer, then:
c9517341 1631
914328ac 1632- First clone the shared repository to a local repository:
c9517341
JH
1633------------------------------------------------
1634$ git clone repo.shared.xz:/pub/scm/project.git/ my-project
1635$ cd my-project
1636$ hack away
1637------------------------------------------------
1638
914328ac
JH
1639- Merge the work others might have done while you were hacking
1640 away:
c9517341
JH
1641------------------------------------------------
1642$ git pull origin
1643$ test the merge result
1644------------------------------------------------
914328ac
JH
1645[NOTE]
1646================================
1647The first `git clone` would have placed the following in
1648`my-project/.git/remotes/origin` file, and that's why this and
1649the next step work.
1650------------
1651URL: repo.shared.xz:/pub/scm/project.git/ my-project
1652Pull: master:origin
1653------------
1654================================
c9517341 1655
914328ac
JH
1656- push your work as the new head of the shared
1657 repository.
c9517341
JH
1658------------------------------------------------
1659$ git push origin master
1660------------------------------------------------
c9517341 1661If somebody else pushed into the same shared repository while
914328ac
JH
1662you were working locally, `git push` in the last step would
1663complain, telling you that the remote `master` head does not
c9517341
JH
1664fast forward. You need to pull and merge those other changes
1665back before you push your work when it happens.
2a29da7c
JH
1666
1667
dc5f9239
JH
1668Advanced Shared Repository Management
1669-------------------------------------
1670
1671Being able to push into a shared repository means being able to
1672write into it. If your developers are coming over the network,
1673this means you, as the repository administrator, need to give
1674each of them an SSH access to the shared repository machine.
1675
1676In some cases, though, you may not want to give a normal shell
1677account to them, but want to restrict them to be able to only
1678do `git push` into the repository and nothing else.
1679
1680You can achieve this by setting the login shell of your
1681developers on the shared repository host to `git-shell` program.
1682
1683[NOTE]
1684Most likely you would also need to list `git-shell` program in
1685`/etc/shells` file.
1686
1687This restricts the set of commands that can be run from incoming
1688SSH connection for these users to only `receive-pack` and
1689`upload-pack`, so the only thing they can do are `git fetch` and
1690`git push`.
1691
1692You still need to create UNIX user accounts for each developer,
1693and put them in the same group. Make sure that the repository
1694shared among these developers is writable by that group.
1695
1696You can implement finer grained branch policies using update
1697hooks. There is a document ("control access to branches") in
1698Documentation/howto by Carl Baldwin and JC outlining how to (1)
1699limit access to branch per user, (2) forbid overwriting existing
1700tags.
1701
1702
6f60300b
JH
1703Bundling your work together
1704---------------------------
1705
1706It is likely that you will be working on more than one thing at
361c06d8 1707a time. It is easy to manage those more-or-less independent tasks
6f60300b
JH
1708using branches with git.
1709
361c06d8 1710We have already seen how branches work previously,
6f60300b
JH
1711with "fun and work" example using two branches. The idea is the
1712same if there are more than two branches. Let's say you started
1713out from "master" head, and have some new code in the "master"
1714branch, and two independent fixes in the "commit-fix" and
1715"diff-fix" branches:
1716
1717------------
1718$ git show-branch
1719! [commit-fix] Fix commit message normalization.
1720 ! [diff-fix] Fix rename detection.
1721 * [master] Release candidate #1
1722---
1723 + [diff-fix] Fix rename detection.
1724 + [diff-fix~1] Better common substring algorithm.
1725+ [commit-fix] Fix commit message normalization.
1726 + [master] Release candidate #1
1727+++ [diff-fix~2] Pretty-print messages.
1728------------
1729
1730Both fixes are tested well, and at this point, you want to merge
1731in both of them. You could merge in 'diff-fix' first and then
1732'commit-fix' next, like this:
1733
1734------------
067744bd
JH
1735$ git merge 'Merge fix in diff-fix' master diff-fix
1736$ git merge 'Merge fix in commit-fix' master commit-fix
6f60300b
JH
1737------------
1738
1739Which would result in:
1740
1741------------
1742$ git show-branch
1743! [commit-fix] Fix commit message normalization.
1744 ! [diff-fix] Fix rename detection.
1745 * [master] Merge fix in commit-fix
1746---
1747 + [master] Merge fix in commit-fix
1748+ + [commit-fix] Fix commit message normalization.
1749 + [master~1] Merge fix in diff-fix
1750 ++ [diff-fix] Fix rename detection.
1751 ++ [diff-fix~1] Better common substring algorithm.
1752 + [master~2] Release candidate #1
1753+++ [master~3] Pretty-print messages.
1754------------
1755
1756However, there is no particular reason to merge in one branch
1757first and the other next, when what you have are a set of truly
1758independent changes (if the order mattered, then they are not
1759independent by definition). You could instead merge those two
1760branches into the current branch at once. First let's undo what
1761we just did and start over. We would want to get the master
1762branch before these two merges by resetting it to 'master~2':
1763
1764------------
1765$ git reset --hard master~2
1766------------
1767
1768You can make sure 'git show-branch' matches the state before
067744bd
JH
1769those two 'git merge' you just did. Then, instead of running
1770two 'git merge' commands in a row, you would pull these two
6f60300b
JH
1771branch heads (this is known as 'making an Octopus'):
1772
1773------------
1774$ git pull . commit-fix diff-fix
1775$ git show-branch
1776! [commit-fix] Fix commit message normalization.
1777 ! [diff-fix] Fix rename detection.
1778 * [master] Octopus merge of branches 'diff-fix' and 'commit-fix'
1779---
1780 + [master] Octopus merge of branches 'diff-fix' and 'commit-fix'
1781+ + [commit-fix] Fix commit message normalization.
1782 ++ [diff-fix] Fix rename detection.
1783 ++ [diff-fix~1] Better common substring algorithm.
1784 + [master~1] Release candidate #1
1785+++ [master~2] Pretty-print messages.
1786------------
1787
1788Note that you should not do Octopus because you can. An octopus
1789is a valid thing to do and often makes it easier to view the
1790commit history if you are pulling more than two independent
1791changes at the same time. However, if you have merge conflicts
1792with any of the branches you are merging in and need to hand
1793resolve, that is an indication that the development happened in
1794those branches were not independent after all, and you should
1795merge two at a time, documenting how you resolved the conflicts,
1796and the reason why you preferred changes made in one side over
1797the other. Otherwise it would make the project history harder
1798to follow, not easier.
1799
3eb5128a 1800[ to be continued.. cvsimports ]