1git-diff-cache(1) 2================= 3v0.1, May 2005 4 5NAME 6---- 7git-diff-cache - Compares content and mode of blobs between the cache and repository 8 9 10SYNOPSIS 11-------- 12'git-diff-cache' [-m] [--cached] [<common diff options>] <tree-ish> [<path>...] 13 14DESCRIPTION 15----------- 16Compares the content and mode of the blobs found via a tree 17object with the content of the current cache and, optionally 18ignoring the stat state of the file on disk. When paths are 19specified, compares only those named paths. Otherwise all 20entries in the cache are compared. 21 22OPTIONS 23------- 24include::diff-options.txt[] 25 26<tree-ish>:: 27 The id of a tree object to diff against. 28 29--cached:: 30 do not consider the on-disk file at all 31 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-cache" say that all non-checked-out files are up 36 to date. 37 38Output format 39------------- 40include::diff-format.txt[] 41 42Operating Modes 43--------------- 44You can choose whether you want to trust the index file entirely 45(using the '--cached' flag) or ask the diff logic to show any files 46that don't match the stat state as being "tentatively changed". Both 47of these operations are very useful indeed. 48 49Cached Mode 50----------- 51If '--cached' is specified, it allows you to ask: 52 53 show me the differences between HEAD and the current index 54 contents (the ones I'd write with a "git-write-tree") 55 56For example, let's say that you have worked on your index file, and are 57ready to commit. You want to see eactly *what* you are going to commit is 58without having to write a new tree object and compare it that way, and to 59do that, you just do 60 61 git-diff-cache --cached $(cat .git/HEAD) 62 63Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 64done an "git-update-cache" to make that effective in the index file. 65"git-diff-files" wouldn't show anything at all, since the index file 66matches my working directory. But doing a "git-diff-cache" does: 67 68 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 69 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 70 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 71 72You can trivially see that the above is a rename. 73 74In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 75actually doing a "git-write-tree" and comparing that. Except this one is much 76nicer for the case where you just want to check where you are. 77 78So doing a "git-diff-cache --cached" is basically very useful when you are 79asking yourself "what have I already marked for being committed, and 80what's the difference to a previous tree". 81 82Non-cached Mode 83--------------- 84The "non-cached" mode takes a different approach, and is potentially 85the more useful of the two in that what it does can't be emulated with 86a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 87The non-cached version asks the question: 88 89 show me the differences between HEAD and the currently checked out 90 tree - index contents _and_ files that aren't up-to-date 91 92which is obviously a very useful question too, since that tells you what 93you *could* commit. Again, the output matches the "git-diff-tree -r" 94output to a tee, but with a twist. 95 96The twist is that if some file doesn't match the cache, we don't have 97a backing store thing for it, and we use the magic "all-zero" sha1 to 98show that. So let's say that you have edited `kernel/sched.c`, but 99have not actually done a "git-update-cache" on it yet - there is no 100"object" associated with the new state, and you get: 101 102 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 103 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 104 105ie it shows that the tree has changed, and that `kernel/sched.c` has is 106not up-to-date and may contain new stuff. The all-zero sha1 means that to 107get the real diff, you need to look at the object in the working directory 108directly rather than do an object-to-object diff. 109 110NOTE! As with other commands of this type, "git-diff-cache" does not 111actually look at the contents of the file at all. So maybe 112`kernel/sched.c` hasn't actually changed, and it's just that you 113touched it. In either case, it's a note that you need to 114"git-upate-cache" it to make the cache be in sync. 115 116NOTE 2! You can have a mixture of files show up as "has been updated" 117and "is still dirty in the working directory" together. You can always 118tell which file is in which state, since the "has been updated" ones 119show a valid sha1, and the "not in sync with the index" ones will 120always have the special all-zero sha1. 121 122 123Author 124------ 125Written by Linus Torvalds <torvalds@osdl.org> 126 127Documentation 128-------------- 129Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 130 131GIT 132--- 133Part of the link:git.html[git] suite 134