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Diffstat (limited to 'Documentation/gitdiffcore.txt')
| -rw-r--r-- | Documentation/gitdiffcore.txt | 86 |
1 files changed, 48 insertions, 38 deletions
diff --git a/Documentation/gitdiffcore.txt b/Documentation/gitdiffcore.txt index e8041bc08f..c579593e55 100644 --- a/Documentation/gitdiffcore.txt +++ b/Documentation/gitdiffcore.txt @@ -3,16 +3,17 @@ gitdiffcore(7) NAME ---- -gitdiffcore - Tweaking diff output (June 2005) +gitdiffcore - Tweaking diff output SYNOPSIS -------- +[verse] 'git diff' * DESCRIPTION ----------- -The diff commands 'git-diff-index', 'git-diff-files', and 'git-diff-tree' +The diff commands 'git diff-index', 'git diff-files', and 'git diff-tree' can be told to manipulate differences they find in unconventional ways before showing 'diff' output. The manipulation is collectively called "diffcore transformation". This short note @@ -23,18 +24,18 @@ that is easier to understand than the conventional kind. The chain of operation ---------------------- -The 'git-diff-{asterisk}' family works by first comparing two sets of +The 'git diff-{asterisk}' family works by first comparing two sets of files: - - 'git-diff-index' compares contents of a "tree" object and the - working directory (when '\--cached' flag is not used) or a - "tree" object and the index file (when '\--cached' flag is + - 'git diff-index' compares contents of a "tree" object and the + working directory (when '--cached' flag is not used) or a + "tree" object and the index file (when '--cached' flag is used); - - 'git-diff-files' compares contents of the index file and the + - 'git diff-files' compares contents of the index file and the working directory; - - 'git-diff-tree' compares contents of two "tree" objects; + - 'git diff-tree' compares contents of two "tree" objects; In all of these cases, the commands themselves first optionally limit the two sets of files by any pathspecs given on their command-lines, @@ -74,12 +75,12 @@ into another list. There are currently 5 such transformations: - diffcore-pickaxe - diffcore-order -These are applied in sequence. The set of filepairs 'git-diff-{asterisk}' +These are applied in sequence. The set of filepairs 'git diff-{asterisk}' commands find are used as the input to diffcore-break, and the output from diffcore-break is used as the input to the next transformation. The final result is then passed to the output routine and generates either diff-raw format (see Output -format sections of the manual for 'git-diff-{asterisk}' commands) or +format sections of the manual for 'git diff-{asterisk}' commands) or diff-patch format. @@ -87,7 +88,7 @@ diffcore-break: For Splitting Up "Complete Rewrites" ---------------------------------------------------- The second transformation in the chain is diffcore-break, and is -controlled by the -B option to the 'git-diff-{asterisk}' commands. This is +controlled by the -B option to the 'git diff-{asterisk}' commands. This is used to detect a filepair that represents "complete rewrite" and break such filepair into two filepairs that represent delete and create. E.g. If the input contained this filepair: @@ -107,7 +108,7 @@ it changes it to: For the purpose of breaking a filepair, diffcore-break examines the extent of changes between the contents of the files before and after modification (i.e. the contents that have "bcd1234..." -and "0123456..." as their SHA1 content ID, in the above +and "0123456..." as their SHA-1 content ID, in the above example). The amount of deletion of original contents and insertion of new material are added together, and if it exceeds the "break score", the filepair is broken into two. The break @@ -123,7 +124,7 @@ diffcore-rename: For Detection Renames and Copies This transformation is used to detect renames and copies, and is controlled by the -M option (to detect renames) and the -C option -(to detect copies as well) to the 'git-diff-{asterisk}' commands. If the +(to detect copies as well) to the 'git diff-{asterisk}' commands. If the input contained these filepairs: ------------------------------------------------ @@ -141,7 +142,7 @@ merges these filepairs and creates: When the "-C" option is used, the original contents of modified files, and deleted files (and also unmodified files, if the -"\--find-copies-harder" option is used) are considered as candidates +"--find-copies-harder" option is used) are considered as candidates of the source files in rename/copy operation. If the input were like these filepairs, that talk about a modified file fileY and a newly created file file0: @@ -167,12 +168,12 @@ a similarity score different from the default of 50% by giving a number after the "-M" or "-C" option (e.g. "-M8" to tell it to use 8/10 = 80%). -Note. When the "-C" option is used with `\--find-copies-harder` -option, 'git-diff-{asterisk}' commands feed unmodified filepairs to +Note. When the "-C" option is used with `--find-copies-harder` +option, 'git diff-{asterisk}' commands feed unmodified filepairs to diffcore mechanism as well as modified ones. This lets the copy detector consider unmodified files as copy source candidates at -the expense of making it slower. Without `\--find-copies-harder`, -'git-diff-{asterisk}' commands can detect copies only if the file that was +the expense of making it slower. Without `--find-copies-harder`, +'git diff-{asterisk}' commands can detect copies only if the file that was copied happened to have been modified in the same changeset. @@ -221,39 +222,48 @@ version prefixed with '+'. diffcore-pickaxe: For Detecting Addition/Deletion of Specified String --------------------------------------------------------------------- -This transformation is used to find filepairs that represent -changes that touch a specified string, and is controlled by the --S option and the `\--pickaxe-all` option to the 'git-diff-{asterisk}' -commands. - -When diffcore-pickaxe is in use, it checks if there are -filepairs whose "original" side has the specified string and -whose "result" side does not. Such a filepair represents "the -string appeared in this changeset". It also checks for the -opposite case that loses the specified string. - -When `\--pickaxe-all` is not in effect, diffcore-pickaxe leaves -only such filepairs that touch the specified string in its -output. When `\--pickaxe-all` is used, diffcore-pickaxe leaves all -filepairs intact if there is such a filepair, or makes the -output empty otherwise. The latter behaviour is designed to -make reviewing of the changes in the context of the whole +This transformation limits the set of filepairs to those that change +specified strings between the preimage and the postimage in a certain +way. -S<block of text> and -G<regular expression> options are used to +specify different ways these strings are sought. + +"-S<block of text>" detects filepairs whose preimage and postimage +have different number of occurrences of the specified block of text. +By definition, it will not detect in-file moves. Also, when a +changeset moves a file wholesale without affecting the interesting +string, diffcore-rename kicks in as usual, and `-S` omits the filepair +(since the number of occurrences of that string didn't change in that +rename-detected filepair). When used with `--pickaxe-regex`, treat +the <block of text> as an extended POSIX regular expression to match, +instead of a literal string. + +"-G<regular expression>" (mnemonic: grep) detects filepairs whose +textual diff has an added or a deleted line that matches the given +regular expression. This means that it will detect in-file (or what +rename-detection considers the same file) moves, which is noise. The +implementation runs diff twice and greps, and this can be quite +expensive. + +When `-S` or `-G` are used without `--pickaxe-all`, only filepairs +that match their respective criterion are kept in the output. When +`--pickaxe-all` is used, if even one filepair matches their respective +criterion in a changeset, the entire changeset is kept. This behavior +is designed to make reviewing changes in the context of the whole changeset easier. - diffcore-order: For Sorting the Output Based on Filenames --------------------------------------------------------- This is used to reorder the filepairs according to the user's (or project's) taste, and is controlled by the -O option to the -'git-diff-{asterisk}' commands. +'git diff-{asterisk}' commands. This takes a text file each of whose lines is a shell glob pattern. Filepairs that match a glob pattern on an earlier line in the file are output before ones that match a later line, and filepairs that do not match any glob pattern are output last. -As an example, a typical orderfile for the core git probably +As an example, a typical orderfile for the core Git probably would look like this: ------------------------------------------------ |