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] [-R] [--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-R:: 40 Output diff in reverse. 41 42--cached:: 43 do not consider the on-disk file at all 44 45-m:: 46 By default, files recorded in the index but not checked 47 out are reported as deleted. This flag makes 48 "git-diff-cache" say that all non-checked-out files are up 49 to date. 50 51Output format 52------------- 53include::diff-format.txt[] 54 55Operating Modes 56--------------- 57You can choose whether you want to trust the index file entirely 58(using the '--cached' flag) or ask the diff logic to show any files 59that don't match the stat state as being "tentatively changed". Both 60of these operations are very useful indeed. 61 62Cached Mode 63----------- 64If '--cached' is specified, it allows you to ask: 65 66 show me the differences between HEAD and the current index 67 contents (the ones I'd write with a "git-write-tree") 68 69For example, let's say that you have worked on your index file, and are 70ready to commit. You want to see eactly *what* you are going to commit is 71without having to write a new tree object and compare it that way, and to 72do that, you just do 73 74 git-diff-cache --cached $(cat .git/HEAD) 75 76Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 77done an "git-update-cache" to make that effective in the index file. 78"git-diff-files" wouldn't show anything at all, since the index file 79matches my working directory. But doing a "git-diff-cache" does: 80 81 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 82 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 83 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 84 85You can trivially see that the above is a rename. 86 87In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 88actually doing a "git-write-tree" and comparing that. Except this one is much 89nicer for the case where you just want to check where you are. 90 91So doing a "git-diff-cache --cached" is basically very useful when you are 92asking yourself "what have I already marked for being committed, and 93what's the difference to a previous tree". 94 95Non-cached Mode 96--------------- 97The "non-cached" mode takes a different approach, and is potentially 98the more useful of the two in that what it does can't be emulated with 99a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 100The non-cached version asks the question: 101 102 show me the differences between HEAD and the currently checked out 103 tree - index contents _and_ files that aren't up-to-date 104 105which is obviously a very useful question too, since that tells you what 106you *could* commit. Again, the output matches the "git-diff-tree -r" 107output to a tee, but with a twist. 108 109The twist is that if some file doesn't match the cache, we don't have 110a backing store thing for it, and we use the magic "all-zero" sha1 to 111show that. So let's say that you have edited `kernel/sched.c`, but 112have not actually done a "git-update-cache" on it yet - there is no 113"object" associated with the new state, and you get: 114 115 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 116 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 117 118ie it shows that the tree has changed, and that `kernel/sched.c` has is 119not up-to-date and may contain new stuff. The all-zero sha1 means that to 120get the real diff, you need to look at the object in the working directory 121directly rather than do an object-to-object diff. 122 123NOTE! As with other commands of this type, "git-diff-cache" does not 124actually look at the contents of the file at all. So maybe 125`kernel/sched.c` hasn't actually changed, and it's just that you 126touched it. In either case, it's a note that you need to 127"git-upate-cache" it to make the cache be in sync. 128 129NOTE 2! You can have a mixture of files show up as "has been updated" 130and "is still dirty in the working directory" together. You can always 131tell which file is in which state, since the "has been updated" ones 132show a valid sha1, and the "not in sync with the index" ones will 133always have the special all-zero sha1. 134 135 136Author 137------ 138Written by Linus Torvalds <torvalds@osdl.org> 139 140Documentation 141-------------- 142Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 143 144GIT 145--- 146Part of the link:git.html[git] suite 147