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diff --git a/Documentation/diffcore.txt b/Documentation/diffcore.txt index 9d20a4f..cb4e562 100644 --- a/Documentation/diffcore.txt +++ b/Documentation/diffcore.txt @@ -6,13 +6,12 @@ June 2005 Introduction ------------ -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(1) output. The -manipulation is collectively called "diffcore transformation". -This short note describes what they are and how to use them to -produce diff outputs that are easier to understand than the -conventional kind. +The diff commands git-diff-index, git-diff-files, git-diff-tree, and +git-diff-stages can be told to manipulate differences they find in +unconventional ways before showing diff(1) output. The manipulation +is collectively called "diffcore transformation". This short note +describes what they are and how to use them to produce diff outputs +that are easier to understand than the conventional kind. The chain of operation @@ -29,7 +28,10 @@ files: - 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; + + - git-diff-stages compares contents of blobs at two stages in an + unmerged index file. In all of these cases, the commands themselves compare corresponding paths in the two sets of files. The result of @@ -65,14 +67,23 @@ format sections of the manual for git-diff-\* commands) or diff-patch format. -diffcore-pathspec ------------------ +diffcore-pathspec: For Ignoring Files Outside Our Consideration +--------------------------------------------------------------- The first transformation in the chain is diffcore-pathspec, and is controlled by giving the pathname parameters to the git-diff-* commands on the command line. The pathspec is used to limit the world diff operates in. It removes the filepairs -outside the specified set of pathnames. +outside the specified set of pathnames. E.g. If the input set +of filepairs included: + +------------------------------------------------ +:100644 100644 bcd1234... 0123456... M junkfile +------------------------------------------------ + +but the command invocation was "git-diff-files myfile", then the +junkfile entry would be removed from the list because only "myfile" +is under consideration. Implementation note. For performance reasons, git-diff-tree uses the pathname parameters on the command line to cull set of @@ -80,8 +91,8 @@ filepairs it feeds the diffcore mechanism itself, and does not use diffcore-pathspec, but the end result is the same. -diffcore-break --------------- +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-* commands. This is @@ -115,8 +126,8 @@ the original is used), and can be customized by giving a number after "-B" option (e.g. "-B75" to tell it to use 75%). -diffcore-rename ---------------- +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 @@ -136,16 +147,16 @@ merges these filepairs and creates: :100644 100644 0123456... 0123456... R100 fileX file0 ------------------------------------------------ -When the "-C" option is used, the original contents of modified -files and contents of unchanged files are considered as -candidates of the source files in rename/copy operation, in -addition to the deleted files. If the input were like these -filepairs, that talk about a modified file fileY and a newly +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 +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: ------------------------------------------------ :100644 100644 0123456... 1234567... M fileY -:000000 100644 0000000... 0123456... A file0 +:000000 100644 0000000... bcd3456... A file0 ------------------------------------------------ the original contents of fileY and the resulting contents of @@ -154,14 +165,14 @@ changed to: ------------------------------------------------ :100644 100644 0123456... 1234567... M fileY -:100644 100644 0123456... 0123456... C100 fileY file0 +:100644 100644 0123456... bcd3456... C100 fileY file0 ------------------------------------------------ In both rename and copy detection, the same "extent of changes" algorithm used in diffcore-break is used to determine if two files are "similar enough", and can be customized to use -similarity score different from the default 50% by giving a -number after "-M" or "-C" option (e.g. "-M8" to tell it to use +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` @@ -173,8 +184,8 @@ git-diff-\* commands can detect copies only if the file that was copied happened to have been modified in the same changeset. -diffcore-merge-broken ---------------------- +diffcore-merge-broken: For Putting "Complete Rewrites" Back Together +-------------------------------------------------------------------- This transformation is used to merge filepairs broken by diffcore-break, and not transformed into rename/copy by @@ -215,8 +226,8 @@ prefixed with '-', followed by the entire contents of new version prefixed with '+'. -diffcore-pickaxe ----------------- +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 @@ -230,7 +241,7 @@ 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 touches the specified string in its +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 @@ -238,19 +249,19 @@ make reviewing of the changes in the context of the whole changeset easier. -diffcore-order --------------- +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-* commands. -This takes a text file each of whose line is a shell glob +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, typical orderfile for the core GIT probably +As an example, a typical orderfile for the core git probably would look like this: ------------------------------------------------ |