Merge git://git.kernel.org/pub/scm/gitk/gitk
[git/git.git] / Documentation / git-diff-index.txt
1 git-diff-index(1)
2 =================
3
4 NAME
5 ----
6 git-diff-index - Compares content and mode of blobs between the index and repository
7
8
9 SYNOPSIS
10 --------
11 'git-diff-index' [-m] [--cached] [<common diff options>] <tree-ish> [<path>...]
12
13 DESCRIPTION
14 -----------
15 Compares the content and mode of the blobs found via a tree
16 object with the content of the current index and, optionally
17 ignoring the stat state of the file on disk. When paths are
18 specified, compares only those named paths. Otherwise all
19 entries in the index are compared.
20
21 OPTIONS
22 -------
23 include::diff-options.txt[]
24
25 <tree-ish>::
26 The id of a tree object to diff against.
27
28 --cached::
29 do not consider the on-disk file at all
30
31 -m::
32 By default, files recorded in the index but not checked
33 out are reported as deleted. This flag makes
34 "git-diff-index" say that all non-checked-out files are up
35 to date.
36
37 Output format
38 -------------
39 include::diff-format.txt[]
40
41 Operating Modes
42 ---------------
43 You can choose whether you want to trust the index file entirely
44 (using the '--cached' flag) or ask the diff logic to show any files
45 that don't match the stat state as being "tentatively changed". Both
46 of these operations are very useful indeed.
47
48 Cached Mode
49 -----------
50 If '--cached' is specified, it allows you to ask:
51
52 show me the differences between HEAD and the current index
53 contents (the ones I'd write with a "git-write-tree")
54
55 For example, let's say that you have worked on your working directory, updated
56 some files in the index and are ready to commit. You want to see exactly
57 *what* you are going to commit is without having to write a new tree
58 object and compare it that way, and to do that, you just do
59
60 git-diff-index --cached HEAD
61
62 Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had
63 done an "git-update-index" to make that effective in the index file.
64 "git-diff-files" wouldn't show anything at all, since the index file
65 matches my working directory. But doing a "git-diff-index" does:
66
67 torvalds@ppc970:~/git> git-diff-index --cached HEAD
68 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c
69 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c
70
71 You can trivially see that the above is a rename.
72
73 In fact, "git-diff-index --cached" *should* always be entirely equivalent to
74 actually doing a "git-write-tree" and comparing that. Except this one is much
75 nicer for the case where you just want to check where you are.
76
77 So doing a "git-diff-index --cached" is basically very useful when you are
78 asking yourself "what have I already marked for being committed, and
79 what's the difference to a previous tree".
80
81 Non-cached Mode
82 ---------------
83 The "non-cached" mode takes a different approach, and is potentially
84 the more useful of the two in that what it does can't be emulated with
85 a "git-write-tree" + "git-diff-tree". Thus that's the default mode.
86 The non-cached version asks the question:
87
88 show me the differences between HEAD and the currently checked out
89 tree - index contents _and_ files that aren't up-to-date
90
91 which is obviously a very useful question too, since that tells you what
92 you *could* commit. Again, the output matches the "git-diff-tree -r"
93 output to a tee, but with a twist.
94
95 The twist is that if some file doesn't match the index, we don't have
96 a backing store thing for it, and we use the magic "all-zero" sha1 to
97 show that. So let's say that you have edited `kernel/sched.c`, but
98 have not actually done a "git-update-index" on it yet - there is no
99 "object" associated with the new state, and you get:
100
101 torvalds@ppc970:~/v2.6/linux> git-diff-index HEAD
102 *100644->100664 blob 7476bb......->000000...... kernel/sched.c
103
104 ie it shows that the tree has changed, and that `kernel/sched.c` has is
105 not up-to-date and may contain new stuff. The all-zero sha1 means that to
106 get the real diff, you need to look at the object in the working directory
107 directly rather than do an object-to-object diff.
108
109 NOTE: As with other commands of this type, "git-diff-index" does not
110 actually look at the contents of the file at all. So maybe
111 `kernel/sched.c` hasn't actually changed, and it's just that you
112 touched it. In either case, it's a note that you need to
113 "git-update-index" it to make the index be in sync.
114
115 NOTE: You can have a mixture of files show up as "has been updated"
116 and "is still dirty in the working directory" together. You can always
117 tell which file is in which state, since the "has been updated" ones
118 show a valid sha1, and the "not in sync with the index" ones will
119 always have the special all-zero sha1.
120
121
122 Author
123 ------
124 Written by Linus Torvalds <torvalds@osdl.org>
125
126 Documentation
127 --------------
128 Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
129
130 GIT
131 ---
132 Part of the gitlink:git[7] suite
133