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] [-O<orderfile>] [-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-O<orderfile>:: 56 Output the patch in the order specified in the 57 <orderfile>, which has one shell glob pattern per line. 58 59-R:: 60 Output diff in reverse. 61 62--cached:: 63 do not consider the on-disk file at all 64 65-m:: 66 By default, files recorded in the index but not checked 67 out are reported as deleted. This flag makes 68 "git-diff-cache" say that all non-checked-out files are up 69 to date. 70 71Output format 72------------- 73include::diff-format.txt[] 74 75Operating Modes 76--------------- 77You can choose whether you want to trust the index file entirely 78(using the '--cached' flag) or ask the diff logic to show any files 79that don't match the stat state as being "tentatively changed". Both 80of these operations are very useful indeed. 81 82Cached Mode 83----------- 84If '--cached' is specified, it allows you to ask: 85 86 show me the differences between HEAD and the current index 87 contents (the ones I'd write with a "git-write-tree") 88 89For example, let's say that you have worked on your index file, and are 90ready to commit. You want to see eactly *what* you are going to commit is 91without having to write a new tree object and compare it that way, and to 92do that, you just do 93 94 git-diff-cache --cached $(cat .git/HEAD) 95 96Example: let's say I had renamed `commit.c` to `git-commit.c`, and I had 97done an "git-update-cache" to make that effective in the index file. 98"git-diff-files" wouldn't show anything at all, since the index file 99matches my working directory. But doing a "git-diff-cache" does: 100 101 torvalds@ppc970:~/git> git-diff-cache --cached $(cat .git/HEAD) 102 -100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 commit.c 103 +100644 blob 4161aecc6700a2eb579e842af0b7f22b98443f74 git-commit.c 104 105You can trivially see that the above is a rename. 106 107In fact, "git-diff-cache --cached" *should* always be entirely equivalent to 108actually doing a "git-write-tree" and comparing that. Except this one is much 109nicer for the case where you just want to check where you are. 110 111So doing a "git-diff-cache --cached" is basically very useful when you are 112asking yourself "what have I already marked for being committed, and 113what's the difference to a previous tree". 114 115Non-cached Mode 116--------------- 117The "non-cached" mode takes a different approach, and is potentially 118the more useful of the two in that what it does can't be emulated with 119a "git-write-tree" + "git-diff-tree". Thus that's the default mode. 120The non-cached version asks the question: 121 122 show me the differences between HEAD and the currently checked out 123 tree - index contents _and_ files that aren't up-to-date 124 125which is obviously a very useful question too, since that tells you what 126you *could* commit. Again, the output matches the "git-diff-tree -r" 127output to a tee, but with a twist. 128 129The twist is that if some file doesn't match the cache, we don't have 130a backing store thing for it, and we use the magic "all-zero" sha1 to 131show that. So let's say that you have edited `kernel/sched.c`, but 132have not actually done a "git-update-cache" on it yet - there is no 133"object" associated with the new state, and you get: 134 135 torvalds@ppc970:~/v2.6/linux> git-diff-cache $(cat .git/HEAD ) 136 *100644->100664 blob 7476bb......->000000...... kernel/sched.c 137 138ie it shows that the tree has changed, and that `kernel/sched.c` has is 139not up-to-date and may contain new stuff. The all-zero sha1 means that to 140get the real diff, you need to look at the object in the working directory 141directly rather than do an object-to-object diff. 142 143NOTE! As with other commands of this type, "git-diff-cache" does not 144actually look at the contents of the file at all. So maybe 145`kernel/sched.c` hasn't actually changed, and it's just that you 146touched it. In either case, it's a note that you need to 147"git-upate-cache" it to make the cache be in sync. 148 149NOTE 2! You can have a mixture of files show up as "has been updated" 150and "is still dirty in the working directory" together. You can always 151tell which file is in which state, since the "has been updated" ones 152show a valid sha1, and the "not in sync with the index" ones will 153always have the special all-zero sha1. 154 155 156Author 157------ 158Written by Linus Torvalds <torvalds@osdl.org> 159 160Documentation 161-------------- 162Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. 163 164GIT 165--- 166Part of the link:git.html[git] suite 167