Minor clarifications in diffcore documentation
Signed-off-by: Chris Shoemaker <c.shoemaker at cox.net> Signed-off-by: Junio C Hamano <junkio@cox.net>
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c.shoemaker@cox.net
Junio C Hamano
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@ -6,13 +6,12 @@ June 2005
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Introduction
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------------
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The diff commands git-diff-index, git-diff-files, and
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git-diff-tree can be told to manipulate differences they find
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in unconventional ways before showing diff(1) output. The
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manipulation is collectively called "diffcore transformation".
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This short note describes what they are and how to use them to
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produce diff outputs that are easier to understand than the
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conventional kind.
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The diff commands git-diff-index, git-diff-files, git-diff-tree, and
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git-diff-stages can be told to manipulate differences they find in
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unconventional ways before showing diff(1) output. The manipulation
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is collectively called "diffcore transformation". This short note
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describes what they are and how to use them to produce diff outputs
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that are easier to understand than the conventional kind.
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The chain of operation
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@ -29,7 +28,10 @@ files:
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- git-diff-files compares contents of the index file and the
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working directory;
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- git-diff-tree compares contents of two "tree" objects.
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- git-diff-tree compares contents of two "tree" objects;
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- git-diff-stages compares contents of blobs at two stages in an
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unmerged index file.
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In all of these cases, the commands themselves compare
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corresponding paths in the two sets of files. The result of
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@ -65,14 +67,23 @@ format sections of the manual for git-diff-\* commands) or
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diff-patch format.
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diffcore-pathspec
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diffcore-pathspec: For Ignoring Files Outside Our Consideration
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-----------------
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The first transformation in the chain is diffcore-pathspec, and
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is controlled by giving the pathname parameters to the
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git-diff-* commands on the command line. The pathspec is used
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to limit the world diff operates in. It removes the filepairs
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outside the specified set of pathnames.
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outside the specified set of pathnames. E.g. If the input set
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of filepairs included:
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------------------------------------------------
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:100644 100644 bcd1234... 0123456... M junkfile
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------------------------------------------------
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but the command invocation was "git-diff-files myfile", then the
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junkfile entry would be removed from the list because only "myfile"
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is under consideration.
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Implementation note. For performance reasons, git-diff-tree
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uses the pathname parameters on the command line to cull set of
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@ -80,7 +91,7 @@ filepairs it feeds the diffcore mechanism itself, and does not
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use diffcore-pathspec, but the end result is the same.
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diffcore-break
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diffcore-break: For Splitting Up "Complete Rewrites"
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--------------
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The second transformation in the chain is diffcore-break, and is
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@ -115,7 +126,7 @@ the original is used), and can be customized by giving a number
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after "-B" option (e.g. "-B75" to tell it to use 75%).
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diffcore-rename
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diffcore-rename: For Detection Renames and Copies
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---------------
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This transformation is used to detect renames and copies, and is
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@ -136,16 +147,16 @@ merges these filepairs and creates:
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:100644 100644 0123456... 0123456... R100 fileX file0
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------------------------------------------------
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When the "-C" option is used, the original contents of modified
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files and contents of unchanged files are considered as
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candidates of the source files in rename/copy operation, in
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addition to the deleted files. If the input were like these
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filepairs, that talk about a modified file fileY and a newly
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When the "-C" option is used, the original contents of modified files,
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and deleted files (and also unmodified files, if the
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"\--find-copies-harder" option is used) are considered as candidates
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of the source files in rename/copy operation. If the input were like
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these filepairs, that talk about a modified file fileY and a newly
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created file file0:
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------------------------------------------------
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:100644 100644 0123456... 1234567... M fileY
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:000000 100644 0000000... 0123456... A file0
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:000000 100644 0000000... bcd3456... A file0
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------------------------------------------------
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the original contents of fileY and the resulting contents of
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@ -154,14 +165,14 @@ changed to:
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------------------------------------------------
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:100644 100644 0123456... 1234567... M fileY
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:100644 100644 0123456... 0123456... C100 fileY file0
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:100644 100644 0123456... bcd3456... C100 fileY file0
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------------------------------------------------
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In both rename and copy detection, the same "extent of changes"
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algorithm used in diffcore-break is used to determine if two
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files are "similar enough", and can be customized to use
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similarity score different from the default 50% by giving a
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number after "-M" or "-C" option (e.g. "-M8" to tell it to use
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a similarity score different from the default of 50% by giving a
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number after the "-M" or "-C" option (e.g. "-M8" to tell it to use
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8/10 = 80%).
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Note. When the "-C" option is used with `\--find-copies-harder`
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@ -173,7 +184,7 @@ git-diff-\* commands can detect copies only if the file that was
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copied happened to have been modified in the same changeset.
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diffcore-merge-broken
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diffcore-merge-broken: For Putting "Complete Rewrites" Back Together
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---------------------
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This transformation is used to merge filepairs broken by
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@ -215,7 +226,7 @@ prefixed with '-', followed by the entire contents of new
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version prefixed with '+'.
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diffcore-pickaxe
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diffcore-pickaxe: For Detecting Addition/Deletion of Specified String
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----------------
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This transformation is used to find filepairs that represent
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@ -230,7 +241,7 @@ string appeared in this changeset". It also checks for the
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opposite case that loses the specified string.
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When `\--pickaxe-all` is not in effect, diffcore-pickaxe leaves
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only such filepairs that touches the specified string in its
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only such filepairs that touch the specified string in its
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output. When `\--pickaxe-all` is used, diffcore-pickaxe leaves all
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filepairs intact if there is such a filepair, or makes the
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output empty otherwise. The latter behaviour is designed to
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@ -238,19 +249,19 @@ make reviewing of the changes in the context of the whole
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changeset easier.
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diffcore-order
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diffcore-order: For Sorting the Output Based on Filenames
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--------------
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This is used to reorder the filepairs according to the user's
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(or project's) taste, and is controlled by the -O option to the
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git-diff-* commands.
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This takes a text file each of whose line is a shell glob
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This takes a text file each of whose lines is a shell glob
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pattern. Filepairs that match a glob pattern on an earlier line
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in the file are output before ones that match a later line, and
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filepairs that do not match any glob pattern are output last.
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As an example, typical orderfile for the core git probably
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As an example, a typical orderfile for the core git probably
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would look like this:
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------------------------------------------------
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