7 git-diff-cache - Compares content and mode of blobs between the cache and repository
12 'git-diff-cache' [-p] [-r] [-z] [-m] [-M] [--cached] <tree-ish>
16 Compares the content and mode of the blobs found via a tree object
17 with the content of the current cache and, optionally ignoring the
18 stat state of the file on disk.
23 The id of a tree object to diff against.
26 Generate patch (see section on generating patches)
29 This flag does not mean anything. It is there only to match
30 "git-diff-tree". Unlike "git-diff-tree", "git-diff-cache"
31 always looks at all the subdirectories.
34 \0 line termination on output
37 Detect renames; implies -p.
40 do not consider the on-disk file at all
43 By default, files recorded in the index but not checked
44 out are reported as deleted. This flag makes
45 "git-diff-cache" say that all non-checked-out files are up
50 include::diff-format.txt[]
54 You can choose whether you want to trust the index file entirely
55 (using the '--cached' flag) or ask the diff logic to show any files
56 that don't match the stat state as being "tentatively changed". Both
57 of these operations are very useful indeed.
61 If '--cached' is specified, it allows you to ask:
63 show me the differences between HEAD and the current index
64 contents (the ones I'd write with a "git-write-tree")
66 For example, let's say that you have worked on your index file, and are
67 ready to commit. You want to see eactly *what* you are going to commit is
68 without having to write a new tree object and compare it that way, and to
71 git-diff-cache --cached $(cat .git/HEAD)
73 Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had
74 done an "git-update-cache" to make that effective in the index file.
75 "git-diff-files" wouldn't show anything at all, since the index file
76 matches my working directory. But doing a "git-diff-cache" does:
78 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD)
79 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c
80 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c
82 You can trivially see that the above is a rename.
84 In fact, "git-diff-cache --cached" *should* always be entirely equivalent to
85 actually doing a "git-write-tree" and comparing that. Except this one is much
86 nicer for the case where you just want to check where you are.
88 So doing a "git-diff-cache --cached" is basically very useful when you are
89 asking yourself "what have I already marked for being committed, and
90 what's the difference to a previous tree".
94 The "non-cached" mode takes a different approach, and is potentially
95 the more useful of the two in that what it does can't be emulated with
96 a "git-write-tree" + "git-diff-tree". Thus that's the default mode.
97 The non-cached version asks the question:
99 show me the differences between HEAD and the currently checked out
100 tree - index contents _and_ files that aren't up-to-date
102 which is obviously a very useful question too, since that tells you what
103 you *could* commit. Again, the output matches the "git-diff-tree -r"
104 output to a tee, but with a twist.
106 The twist is that if some file doesn't match the cache, we don't have
107 a backing store thing for it, and we use the magic "all-zero" sha1 to
108 show that. So let's say that you have edited `kernel/sched.c`, but
109 have not actually done a "git-update-cache" on it yet - there is no
110 "object" associated with the new state, and you get:
112 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD )
113 *100644->100664 blob 7476bb......->000000...... kernel/sched.c
115 ie it shows that the tree has changed, and that `kernel/sched.c` has is
116 not up-to-date and may contain new stuff. The all-zero sha1 means that to
117 get the real diff, you need to look at the object in the working directory
118 directly rather than do an object-to-object diff.
120 NOTE! As with other commands of this type, "git-diff-cache" does not
121 actually look at the contents of the file at all. So maybe
122 `kernel/sched.c` hasn't actually changed, and it's just that you
123 touched it. In either case, it's a note that you need to
124 "git-upate-cache" it to make the cache be in sync.
126 NOTE 2! You can have a mixture of files show up as "has been updated"
127 and "is still dirty in the working directory" together. You can always
128 tell which file is in which state, since the "has been updated" ones
129 show a valid sha1, and the "not in sync with the index" ones will
130 always have the special all-zero sha1.
135 Written by Linus Torvalds <torvalds@osdl.org>
139 Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
143 Part of the link:git.html[git] suite