git-diff-index(1) ================= NAME ---- git-diff-index - Compares content and mode of blobs between the cache and repository SYNOPSIS -------- 'git-diff-index' [-m] [--cached] [] [...] DESCRIPTION ----------- Compares the content and mode of the blobs found via a tree object with the content of the current cache and, optionally ignoring the stat state of the file on disk. When paths are specified, compares only those named paths. Otherwise all entries in the cache are compared. OPTIONS ------- include::diff-options.txt[] :: The id of a tree object to diff against. --cached:: do not consider the on-disk file at all -m:: By default, files recorded in the index but not checked out are reported as deleted. This flag makes "git-diff-index" say that all non-checked-out files are up to date. Output format ------------- include::diff-format.txt[] Operating Modes --------------- You can choose whether you want to trust the index file entirely (using the '--cached' flag) or ask the diff logic to show any files that don't match the stat state as being "tentatively changed". Both of these operations are very useful indeed. Cached Mode ----------- If '--cached' is specified, it allows you to ask: show me the differences between HEAD and the current cache contents (the ones I'd write with a "git-write-tree") For example, let's say that you have worked on your working directory, updated some files in the cache and are ready to commit. You want to see eactly *what* you are going to commit is without having to write a new tree object and compare it that way, and to do that, you just do git-diff-index --cached $(cat .git/HEAD) Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had done an "git-update-index" to make that effective in the index file. "git-diff-files" wouldn't show anything at all, since the index file matches my working directory. But doing a "git-diff-index" does: torvalds@ppc970:~/git> git-diff-index --cached $(cat .git/HEAD) -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c You can trivially see that the above is a rename. In fact, "git-diff-index --cached" *should* always be entirely equivalent to actually doing a "git-write-tree" and comparing that. Except this one is much nicer for the case where you just want to check where you are. So doing a "git-diff-index --cached" is basically very useful when you are asking yourself "what have I already marked for being committed, and what's the difference to a previous tree". Non-cached Mode --------------- The "non-cached" mode takes a different approach, and is potentially the more useful of the two in that what it does can't be emulated with a "git-write-tree" + "git-diff-tree". Thus that's the default mode. The non-cached version asks the question: show me the differences between HEAD and the currently checked out tree - index contents _and_ files that aren't up-to-date which is obviously a very useful question too, since that tells you what you *could* commit. Again, the output matches the "git-diff-tree -r" output to a tee, but with a twist. The twist is that if some file doesn't match the cache, we don't have a backing store thing for it, and we use the magic "all-zero" sha1 to show that. So let's say that you have edited `kernel/sched.c`, but have not actually done a "git-update-index" on it yet - there is no "object" associated with the new state, and you get: torvalds@ppc970:~/v2.6/linux> git-diff-index $(cat .git/HEAD ) *100644->100664 blob 7476bb......->000000...... kernel/sched.c ie it shows that the tree has changed, and that `kernel/sched.c` has is not up-to-date and may contain new stuff. The all-zero sha1 means that to get the real diff, you need to look at the object in the working directory directly rather than do an object-to-object diff. NOTE: As with other commands of this type, "git-diff-index" does not actually look at the contents of the file at all. So maybe `kernel/sched.c` hasn't actually changed, and it's just that you touched it. In either case, it's a note that you need to "git-upate-cache" it to make the cache be in sync. NOTE: You can have a mixture of files show up as "has been updated" and "is still dirty in the working directory" together. You can always tell which file is in which state, since the "has been updated" ones show a valid sha1, and the "not in sync with the index" ones will always have the special all-zero sha1. Author ------ Written by Linus Torvalds Documentation -------------- Documentation by David Greaves, Junio C Hamano and the git-list . GIT --- Part of the gitlink:git[7] suite