Merge master.kernel.org:/pub/scm/gitk/gitk
[git/git.git] / Documentation / git-diff-cache.txt
1 git-diff-cache(1)
2 =================
3 v0.1, May 2005
4
5 NAME
6 ----
7 git-diff-cache - Compares content and mode of blobs between the cache and repository
8
9
10 SYNOPSIS
11 --------
12 'git-diff-cache' [-p] [-r] [-z] [-m] [--cached] [-R] [-B] [-M] [-C] [--find-copies-harder] [-O<orderfile>] [-S<string>] [--pickaxe-all] <tree-ish> [<path>...]
13
14 DESCRIPTION
15 -----------
16 Compares the content and mode of the blobs found via a tree
17 object with the content of the current cache and, optionally
18 ignoring the stat state of the file on disk. When paths are
19 specified, compares only those named paths. Otherwise all
20 entries in the cache are compared.
21
22 OPTIONS
23 -------
24 <tree-ish>::
25 The id of a tree object to diff against.
26
27 -p::
28 Generate patch (see section on generating patches)
29
30 -r::
31 This flag does not mean anything. It is there only to match
32 "git-diff-tree". Unlike "git-diff-tree", "git-diff-cache"
33 always looks at all the subdirectories.
34
35 -z::
36 \0 line termination on output
37
38 -B::
39 Break complete rewrite changes into pairs of delete and create.
40
41 -M::
42 Detect renames.
43
44 -C::
45 Detect copies as well as renames.
46
47 --find-copies-harder::
48 By default, -C option finds copies only if the original
49 file of the copy was modified in the same changeset for
50 performance reasons. This flag makes the command
51 inspect unmodified files as candidates for the source of
52 copy. This is a very expensive operation for large
53 projects, so use it with caution.
54
55 -S<string>::
56 Look for differences that contains the change in <string>.
57
58 --pickaxe-all::
59 When -S finds a change, show all the changes in that
60 changeset, not just the files that contains the change
61 in <string>.
62
63 -O<orderfile>::
64 Output the patch in the order specified in the
65 <orderfile>, which has one shell glob pattern per line.
66
67 -R::
68 Swap two inputs; that is, show differences from cache or
69 on-disk file to tree contents.
70
71 --cached::
72 do not consider the on-disk file at all
73
74 -m::
75 By default, files recorded in the index but not checked
76 out are reported as deleted. This flag makes
77 "git-diff-cache" say that all non-checked-out files are up
78 to date.
79
80 Output format
81 -------------
82 include::diff-format.txt[]
83
84 Operating Modes
85 ---------------
86 You can choose whether you want to trust the index file entirely
87 (using the '--cached' flag) or ask the diff logic to show any files
88 that don't match the stat state as being "tentatively changed". Both
89 of these operations are very useful indeed.
90
91 Cached Mode
92 -----------
93 If '--cached' is specified, it allows you to ask:
94
95 show me the differences between HEAD and the current index
96 contents (the ones I'd write with a "git-write-tree")
97
98 For example, let's say that you have worked on your index file, and are
99 ready to commit. You want to see eactly *what* you are going to commit is
100 without having to write a new tree object and compare it that way, and to
101 do that, you just do
102
103 git-diff-cache --cached $(cat .git/HEAD)
104
105 Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had
106 done an "git-update-cache" to make that effective in the index file.
107 "git-diff-files" wouldn't show anything at all, since the index file
108 matches my working directory. But doing a "git-diff-cache" does:
109
110 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD)
111 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c
112 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c
113
114 You can trivially see that the above is a rename.
115
116 In fact, "git-diff-cache --cached" *should* always be entirely equivalent to
117 actually doing a "git-write-tree" and comparing that. Except this one is much
118 nicer for the case where you just want to check where you are.
119
120 So doing a "git-diff-cache --cached" is basically very useful when you are
121 asking yourself "what have I already marked for being committed, and
122 what's the difference to a previous tree".
123
124 Non-cached Mode
125 ---------------
126 The "non-cached" mode takes a different approach, and is potentially
127 the more useful of the two in that what it does can't be emulated with
128 a "git-write-tree" + "git-diff-tree". Thus that's the default mode.
129 The non-cached version asks the question:
130
131 show me the differences between HEAD and the currently checked out
132 tree - index contents _and_ files that aren't up-to-date
133
134 which is obviously a very useful question too, since that tells you what
135 you *could* commit. Again, the output matches the "git-diff-tree -r"
136 output to a tee, but with a twist.
137
138 The twist is that if some file doesn't match the cache, we don't have
139 a backing store thing for it, and we use the magic "all-zero" sha1 to
140 show that. So let's say that you have edited `kernel/sched.c`, but
141 have not actually done a "git-update-cache" on it yet - there is no
142 "object" associated with the new state, and you get:
143
144 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD )
145 *100644->100664 blob 7476bb......->000000...... kernel/sched.c
146
147 ie it shows that the tree has changed, and that `kernel/sched.c` has is
148 not up-to-date and may contain new stuff. The all-zero sha1 means that to
149 get the real diff, you need to look at the object in the working directory
150 directly rather than do an object-to-object diff.
151
152 NOTE! As with other commands of this type, "git-diff-cache" does not
153 actually look at the contents of the file at all. So maybe
154 `kernel/sched.c` hasn't actually changed, and it's just that you
155 touched it. In either case, it's a note that you need to
156 "git-upate-cache" it to make the cache be in sync.
157
158 NOTE 2! You can have a mixture of files show up as "has been updated"
159 and "is still dirty in the working directory" together. You can always
160 tell which file is in which state, since the "has been updated" ones
161 show a valid sha1, and the "not in sync with the index" ones will
162 always have the special all-zero sha1.
163
164
165 Author
166 ------
167 Written by Linus Torvalds <torvalds@osdl.org>
168
169 Documentation
170 --------------
171 Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
172
173 GIT
174 ---
175 Part of the link:git.html[git] suite
176