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' [-p] [-r] [-z] [-m] [-M] [--cached] <tree-ish> 13 14DESCRIPTION 15----------- 16Compares the content and mode of the blobs found via a tree object 17with the content of the current cache and, optionally ignoring the 18stat state of the file on disk. 19 20OPTIONS 21------- 22<tree-ish>:: 23 The id of a tree object to diff against. 24 25-p:: 26 Generate patch (see section on generating patches) 27 28-r:: 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. 32 33-z:: 34 \0 line termination on output 35 36-M:: 37 Detect renames; implies -p. 38 39--cached:: 40 do not consider the on-disk file at all 41 42-m:: 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 46 to date. 47 48Output format 49------------- 50include::diff-format.txt[] 51 52Operating Modes 53--------------- 54You 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 56that don't match the stat state as being "tentatively changed". Both 57of these operations are very useful indeed. 58 59Cached Mode 60----------- 61If '--cached' is specified, it allows you to ask: 62 63 show me the differences between HEAD and the current index 64 contents (the ones I'd write with a "git-write-tree") 65 66For example, let's say that you have worked on your index file, and are 67ready to commit. You want to see eactly *what* you are going to commit is 68without having to write a new tree object and compare it that way, and to 69do that, you just do 70 71 git-diff-cache --cached $(cat .git/HEAD) 72 73Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 74done 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 76matches my working directory. But doing a "git-diff-cache" does: 77 78 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 79 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 80 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 81 82You can trivially see that the above is a rename. 83 84In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 85actually doing a "git-write-tree" and comparing that. Except this one is much 86nicer for the case where you just want to check where you are. 87 88So doing a "git-diff-cache --cached" is basically very useful when you are 89asking yourself "what have I already marked for being committed, and 90what's the difference to a previous tree". 91 92Non-cached Mode 93--------------- 94The "non-cached" mode takes a different approach, and is potentially 95the more useful of the two in that what it does can't be emulated with 96a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 97The non-cached version asks the question: 98 99 show me the differences between HEAD and the currently checked out 100 tree - index contents _and_ files that aren't up-to-date 101 102which is obviously a very useful question too, since that tells you what 103you *could* commit. Again, the output matches the "git-diff-tree -r" 104output to a tee, but with a twist. 105 106The twist is that if some file doesn't match the cache, we don't have 107a backing store thing for it, and we use the magic "all-zero" sha1 to 108show that. So let's say that you have edited `kernel/sched.c`, but 109have not actually done a "git-update-cache" on it yet - there is no 110"object" associated with the new state, and you get: 111 112 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 113 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 114 115ie it shows that the tree has changed, and that `kernel/sched.c` has is 116not up-to-date and may contain new stuff. The all-zero sha1 means that to 117get the real diff, you need to look at the object in the working directory 118directly rather than do an object-to-object diff. 119 120NOTE! As with other commands of this type, "git-diff-cache" does not 121actually 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 123touched it. In either case, it's a note that you need to 124"git-upate-cache" it to make the cache be in sync. 125 126NOTE 2! You can have a mixture of files show up as "has been updated" 127and "is still dirty in the working directory" together. You can always 128tell which file is in which state, since the "has been updated" ones 129show a valid sha1, and the "not in sync with the index" ones will 130always have the special all-zero sha1. 131 132 133Author 134------ 135Written by Linus Torvalds <torvalds@osdl.org> 136 137Documentation 138-------------- 139Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 140 141GIT 142--- 143Part of the link:git.html[git] suite 144