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] [-C] [-S<string>] [--cached] <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------- 24<tree-ish>:: 25 The id of a tree object to diff against. 26 27-p:: 28 Generate patch (see section on generating patches) 29 30-r:: 31 This flag does not mean anything. It is there only to match 32 "git-diff-tree". Unlike "git-diff-tree", "git-diff-cache" 33 always looks at all the subdirectories. 34 35-z:: 36 \0 line termination on output 37 38-M:: 39 Detect renames. 40 41-C:: 42 Detect copies as well as renames. 43 44-S<string>:: 45 Look for differences that contains the change in <string>. 46 47 48-R:: 49 Output diff in reverse. 50 51--cached:: 52 do not consider the on-disk file at all 53 54-m:: 55 By default, files recorded in the index but not checked 56 out are reported as deleted. This flag makes 57 "git-diff-cache" say that all non-checked-out files are up 58 to date. 59 60Output format 61------------- 62include::diff-format.txt[] 63 64Operating Modes 65--------------- 66You can choose whether you want to trust the index file entirely 67(using the '--cached' flag) or ask the diff logic to show any files 68that don't match the stat state as being "tentatively changed". Both 69of these operations are very useful indeed. 70 71Cached Mode 72----------- 73If '--cached' is specified, it allows you to ask: 74 75 show me the differences between HEAD and the current index 76 contents (the ones I'd write with a "git-write-tree") 77 78For example, let's say that you have worked on your index file, and are 79ready to commit. You want to see eactly *what* you are going to commit is 80without having to write a new tree object and compare it that way, and to 81do that, you just do 82 83 git-diff-cache --cached $(cat .git/HEAD) 84 85Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 86done an "git-update-cache" to make that effective in the index file. 87"git-diff-files" wouldn't show anything at all, since the index file 88matches my working directory. But doing a "git-diff-cache" does: 89 90 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 91 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 92 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 93 94You can trivially see that the above is a rename. 95 96In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 97actually doing a "git-write-tree" and comparing that. Except this one is much 98nicer for the case where you just want to check where you are. 99 100So doing a "git-diff-cache --cached" is basically very useful when you are 101asking yourself "what have I already marked for being committed, and 102what's the difference to a previous tree". 103 104Non-cached Mode 105--------------- 106The "non-cached" mode takes a different approach, and is potentially 107the more useful of the two in that what it does can't be emulated with 108a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 109The non-cached version asks the question: 110 111 show me the differences between HEAD and the currently checked out 112 tree - index contents _and_ files that aren't up-to-date 113 114which is obviously a very useful question too, since that tells you what 115you *could* commit. Again, the output matches the "git-diff-tree -r" 116output to a tee, but with a twist. 117 118The twist is that if some file doesn't match the cache, we don't have 119a backing store thing for it, and we use the magic "all-zero" sha1 to 120show that. So let's say that you have edited `kernel/sched.c`, but 121have not actually done a "git-update-cache" on it yet - there is no 122"object" associated with the new state, and you get: 123 124 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 125 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 126 127ie it shows that the tree has changed, and that `kernel/sched.c` has is 128not up-to-date and may contain new stuff. The all-zero sha1 means that to 129get the real diff, you need to look at the object in the working directory 130directly rather than do an object-to-object diff. 131 132NOTE! As with other commands of this type, "git-diff-cache" does not 133actually look at the contents of the file at all. So maybe 134`kernel/sched.c` hasn't actually changed, and it's just that you 135touched it. In either case, it's a note that you need to 136"git-upate-cache" it to make the cache be in sync. 137 138NOTE 2! You can have a mixture of files show up as "has been updated" 139and "is still dirty in the working directory" together. You can always 140tell which file is in which state, since the "has been updated" ones 141show a valid sha1, and the "not in sync with the index" ones will 142always have the special all-zero sha1. 143 144 145Author 146------ 147Written by Linus Torvalds <torvalds@osdl.org> 148 149Documentation 150-------------- 151Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 152 153GIT 154--- 155Part of the link:git.html[git] suite 156