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