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