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] [-B] [-M] [-R] [-C] [-S<string>] [--pickaxe-all] [--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-B:: 39 Break complete rewrite changes into pairs of delete and create. 40 41-M:: 42 Detect renames. 43 44-C:: 45 Detect copies as well as renames. 46 47-S<string>:: 48 Look for differences that contains the change in <string>. 49 50--pickaxe-all:: 51 When -S finds a change, show all the changes in that 52 changeset, not just the files that contains the change 53 in <string>. 54 55-R:: 56 Output diff in reverse. 57 58--cached:: 59 do not consider the on-disk file at all 60 61-m:: 62 By default, files recorded in the index but not checked 63 out are reported as deleted. This flag makes 64 "git-diff-cache" say that all non-checked-out files are up 65 to date. 66 67Output format 68------------- 69include::diff-format.txt[] 70 71Operating Modes 72--------------- 73You can choose whether you want to trust the index file entirely 74(using the '--cached' flag) or ask the diff logic to show any files 75that don't match the stat state as being "tentatively changed". Both 76of these operations are very useful indeed. 77 78Cached Mode 79----------- 80If '--cached' is specified, it allows you to ask: 81 82 show me the differences between HEAD and the current index 83 contents (the ones I'd write with a "git-write-tree") 84 85For example, let's say that you have worked on your index file, and are 86ready to commit. You want to see eactly *what* you are going to commit is 87without having to write a new tree object and compare it that way, and to 88do that, you just do 89 90 git-diff-cache --cached $(cat .git/HEAD) 91 92Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 93done an "git-update-cache" to make that effective in the index file. 94"git-diff-files" wouldn't show anything at all, since the index file 95matches my working directory. But doing a "git-diff-cache" does: 96 97 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 98 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 99 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 100 101You can trivially see that the above is a rename. 102 103In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 104actually doing a "git-write-tree" and comparing that. Except this one is much 105nicer for the case where you just want to check where you are. 106 107So doing a "git-diff-cache --cached" is basically very useful when you are 108asking yourself "what have I already marked for being committed, and 109what's the difference to a previous tree". 110 111Non-cached Mode 112--------------- 113The "non-cached" mode takes a different approach, and is potentially 114the more useful of the two in that what it does can't be emulated with 115a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 116The non-cached version asks the question: 117 118 show me the differences between HEAD and the currently checked out 119 tree - index contents _and_ files that aren't up-to-date 120 121which is obviously a very useful question too, since that tells you what 122you *could* commit. Again, the output matches the "git-diff-tree -r" 123output to a tee, but with a twist. 124 125The twist is that if some file doesn't match the cache, we don't have 126a backing store thing for it, and we use the magic "all-zero" sha1 to 127show that. So let's say that you have edited `kernel/sched.c`, but 128have not actually done a "git-update-cache" on it yet - there is no 129"object" associated with the new state, and you get: 130 131 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 132 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 133 134ie it shows that the tree has changed, and that `kernel/sched.c` has is 135not up-to-date and may contain new stuff. The all-zero sha1 means that to 136get the real diff, you need to look at the object in the working directory 137directly rather than do an object-to-object diff. 138 139NOTE! As with other commands of this type, "git-diff-cache" does not 140actually look at the contents of the file at all. So maybe 141`kernel/sched.c` hasn't actually changed, and it's just that you 142touched it. In either case, it's a note that you need to 143"git-upate-cache" it to make the cache be in sync. 144 145NOTE 2! You can have a mixture of files show up as "has been updated" 146and "is still dirty in the working directory" together. You can always 147tell which file is in which state, since the "has been updated" ones 148show a valid sha1, and the "not in sync with the index" ones will 149always have the special all-zero sha1. 150 151 152Author 153------ 154Written by Linus Torvalds <torvalds@osdl.org> 155 156Documentation 157-------------- 158Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 159 160GIT 161--- 162Part of the link:git.html[git] suite 163