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