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