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] [--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--cached:: 37 do not consider the on-disk file at all 38 39-m:: 40 By default, files recorded in the index but not checked 41 out are reported as deleted. This flag makes 42 "git-diff-cache" say that all non-checked-out files are up 43 to date. 44 45Output format 46------------- 47include::diff-format.txt[] 48 49Operating Modes 50--------------- 51You can choose whether you want to trust the index file entirely 52(using the '--cached' flag) or ask the diff logic to show any files 53that don't match the stat state as being "tentatively changed". Both 54of these operations are very useful indeed. 55 56Cached Mode 57----------- 58If '--cached' is specified, it allows you to ask: 59 60 show me the differences between HEAD and the current index 61 contents (the ones I'd write with a "git-write-tree") 62 63For example, let's say that you have worked on your index file, and are 64ready to commit. You want to see eactly *what* you are going to commit is 65without having to write a new tree object and compare it that way, and to 66do that, you just do 67 68 git-diff-cache --cached $(cat .git/HEAD) 69 70Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 71done an "git-update-cache" to make that effective in the index file. 72"git-diff-files" wouldn't show anything at all, since the index file 73matches my working directory. But doing a "git-diff-cache" does: 74 75 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 76 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 77 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 78 79You can trivially see that the above is a rename. 80 81In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 82actually doing a "git-write-tree" and comparing that. Except this one is much 83nicer for the case where you just want to check where you are. 84 85So doing a "git-diff-cache --cached" is basically very useful when you are 86asking yourself "what have I already marked for being committed, and 87what's the difference to a previous tree". 88 89Non-cached Mode 90--------------- 91The "non-cached" mode takes a different approach, and is potentially 92the more useful of the two in that what it does can't be emulated with 93a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 94The non-cached version asks the question: 95 96 show me the differences between HEAD and the currently checked out 97 tree - index contents _and_ files that aren't up-to-date 98 99which is obviously a very useful question too, since that tells you what 100you *could* commit. Again, the output matches the "git-diff-tree -r" 101output to a tee, but with a twist. 102 103The twist is that if some file doesn't match the cache, we don't have 104a backing store thing for it, and we use the magic "all-zero" sha1 to 105show that. So let's say that you have edited `kernel/sched.c`, but 106have not actually done a "git-update-cache" on it yet - there is no 107"object" associated with the new state, and you get: 108 109 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 110 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 111 112ie it shows that the tree has changed, and that `kernel/sched.c` has is 113not up-to-date and may contain new stuff. The all-zero sha1 means that to 114get the real diff, you need to look at the object in the working directory 115directly rather than do an object-to-object diff. 116 117NOTE! As with other commands of this type, "git-diff-cache" does not 118actually look at the contents of the file at all. So maybe 119`kernel/sched.c` hasn't actually changed, and it's just that you 120touched it. In either case, it's a note that you need to 121"git-upate-cache" it to make the cache be in sync. 122 123NOTE 2! You can have a mixture of files show up as "has been updated" 124and "is still dirty in the working directory" together. You can always 125tell which file is in which state, since the "has been updated" ones 126show a valid sha1, and the "not in sync with the index" ones will 127always have the special all-zero sha1. 128 129 130Author 131------ 132Written by Linus Torvalds <torvalds@osdl.org> 133 134Documentation 135-------------- 136Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 137 138GIT 139--- 140Part of the link:git.html[git] suite 141