git-svn: support -C<num> passing to git-diff-tree

[git.git] / Documentation / diffcore.txt

diff --git a/Documentation/diffcore.txt b/Documentation/diffcore.txt
index 6c474d1..cb4e562 100644 (file)
--- a/Documentation/diffcore.txt
+++ b/Documentation/diffcore.txt
@@ -6,13 +6,12 @@ June 2005
 Introduction
 ------------
 
 Introduction
 ------------
 

-The diff commands git-diff-cache, 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
 
 
 The chain of operation


@@ -21,15 +20,18 @@ The chain of operation
 The git-diff-* family works by first comparing two sets of
 files:
 
 The git-diff-* family works by first comparing two sets of
 files:
 

- - git-diff-cache 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
    working directory;
 
    used);
 
  - 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
 
 In all of these cases, the commands themselves compare
 corresponding paths in the two sets of files.  The result of


@@ -37,40 +39,51 @@ comparison is passed from these commands to what is internally
 called "diffcore", in a format similar to what is output when
 the -p option is not used.  E.g.
 
 called "diffcore", in a format similar to what is output when
 the -p option is not used.  E.g.
 

-    in-place edit  :100644 100644 bcd1234... 0123456... M file0
-    create         :000000 100644 0000000... 1234567... N file4
-    delete         :100644 000000 1234567... 0000000... D file5
-    unmerged       :000000 000000 0000000... 0000000... U file6
+------------------------------------------------
+in-place edit  :100644 100644 bcd1234... 0123456... M file0
+create         :000000 100644 0000000... 1234567... A file4
+delete         :100644 000000 1234567... 0000000... D file5
+unmerged       :000000 000000 0000000... 0000000... U file6
+------------------------------------------------

 
 The diffcore mechanism is fed a list of such comparison results
 (each of which is called "filepair", although at this point each
 of them talks about a single file), and transforms such a list
 into another list.  There are currently 6 such transformations:
 
 
 The diffcore mechanism is fed a list of such comparison results
 (each of which is called "filepair", although at this point each
 of them talks about a single file), and transforms such a list
 into another list.  There are currently 6 such transformations:
 

- - diffcore-pathspec
- - diffcore-break
- - diffcore-rename
- - diffcore-merge-broken
- - diffcore-pickaxe
- - diffcore-order
+- diffcore-pathspec
+- diffcore-break
+- diffcore-rename
+- diffcore-merge-broken
+- diffcore-pickaxe
+- diffcore-order

 
 

-These are applied in sequence.  The set of filepairs git-diff-*
+These are applied in sequence.  The set of filepairs git-diff-\*

 commands find are used as the input to diffcore-pathspec, and
 the output from diffcore-pathspec 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
 commands find are used as the input to diffcore-pathspec, and
 the output from diffcore-pathspec 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-* commands) or
+format sections of the manual for git-diff-\* commands) or

 diff-patch format.
 
 
 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
 
 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
 
 Implementation note.  For performance reasons, git-diff-tree
 uses the pathname parameters on the command line to cull set of


@@ -78,8 +91,8 @@ filepairs it feeds the diffcore mechanism itself, and does not
 use diffcore-pathspec, but the end result is the same.
 
 
 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
 
 The second transformation in the chain is diffcore-break, and is
 controlled by the -B option to the git-diff-* commands.  This is


@@ -87,13 +100,17 @@ 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:
 
 break such filepair into two filepairs that represent delete and
 create.  E.g.  If the input contained this filepair:
 

-    :100644 100644 bcd1234... 0123456... M file0
+------------------------------------------------
+:100644 100644 bcd1234... 0123456... M file0
+------------------------------------------------

 
 and if it detects that the file "file0" is completely rewritten,
 it changes it to:
 
 
 and if it detects that the file "file0" is completely rewritten,
 it changes it to:
 

-    :100644 000000 bcd1234... 0000000... D file0
-    :000000 100644 0000000... 0123456... N file0
+------------------------------------------------
+:100644 000000 bcd1234... 0000000... D file0
+:000000 100644 0000000... 0123456... A file0
+------------------------------------------------

 
 For the purpose of breaking a filepair, diffcore-break examines
 the extent of changes between the contents of the files before
 
 For the purpose of breaking a filepair, diffcore-break examines
 the extent of changes between the contents of the files before


@@ -109,61 +126,69 @@ the original is used), and can be customized by giving a number
 after "-B" option (e.g. "-B75" to tell it to use 75%).
 
 
 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
 (to detect copies as well) to the git-diff-* commands.  If the
 input contained these filepairs:
 
 
 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-* commands.  If the
 input contained these filepairs:
 

-    :100644 000000 0123456... 0000000... D fileX
-    :000000 100644 0000000... 0123456... N file0
+------------------------------------------------
+:100644 000000 0123456... 0000000... D fileX
+:000000 100644 0000000... 0123456... A file0
+------------------------------------------------

 
 and the contents of the deleted file fileX is similar enough to
 the contents of the created file file0, then rename detection
 merges these filepairs and creates:
 
 
 and the contents of the deleted file fileX is similar enough to
 the contents of the created file file0, then rename detection
 merges these filepairs and creates:
 

-    :100644 100644 0123456... 0123456... R100 fileX file0
+------------------------------------------------
+: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:
 
 created file file0:
 

-    :100644 100644 0123456... 1234567... M fileY
-    :000000 100644 0000000... 0123456... N file0
+------------------------------------------------
+:100644 100644 0123456... 1234567... M fileY
+:000000 100644 0000000... bcd3456... A file0
+------------------------------------------------

 
 the original contents of fileY and the resulting contents of
 file0 are compared, and if they are similar enough, they are
 changed to:
 
 
 the original contents of fileY and the resulting contents of
 file0 are compared, and if they are similar enough, they are
 changed to:
 

-    :100644 100644 0123456... 1234567... M fileY
-    :100644 100644 0123456... 0123456... C100 fileY file0
+------------------------------------------------
+:100644 100644 0123456... 1234567... M fileY
+: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
 
 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%).
 
 8/10 = 80%).
 

-Note.  When the "-C" option is used with --find-copies-harder
-option, git-diff-* commands feed unmodified filepairs to
+Note.  When the "-C" option is used with `\--find-copies-harder`
+option, git-diff-\* 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
 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-* commands can detect copies only if the file that was
+the expense of making it slower.  Without `\--find-copies-harder`,
+git-diff-\* commands can detect copies only if the file that was

 copied happened to have been modified in the same changeset.
 
 
 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
 
 This transformation is used to merge filepairs broken by

-diffcore-break, and were not transformed into rename/copy by
+diffcore-break, and not transformed into rename/copy by

 diffcore-rename, back into a single modification.  This always
 runs when diffcore-break is used.
 
 diffcore-rename, back into a single modification.  This always
 runs when diffcore-break is used.
 


@@ -186,27 +211,27 @@ material is deleted, the broken pairs are merged back into a
 single modification) by giving a second number to -B option,
 like these:
 
 single modification) by giving a second number to -B option,
 like these:
 

-       -B50/60 (give 50% "break score" to diffcore-break, use
-                 60% for diffcore-merge-broken).
-       -B/60   (the same as above, since diffcore-break defautls to
-                50%).
+* -B50/60 (give 50% "break score" to diffcore-break, use 60%
+  for diffcore-merge-broken).
+
+* -B/60 (the same as above, since diffcore-break defaults to 50%).

 
 Note that earlier implementation left a broken pair as a separate
 
 Note that earlier implementation left a broken pair as a separate

-creation and deletion patches.  This was unnecessary hack and
+creation and deletion patches.  This was an unnecessary hack and

 the latest implementation always merges all the broken pairs
 back into modifications, but the resulting patch output is
 the latest implementation always merges all the broken pairs
 back into modifications, but the resulting patch output is

-formatted differently to still let the reviewing easier for such
+formatted differently for easier review in case of such

 a complete rewrite by showing the entire contents of old version
 prefixed with '-', followed by the entire contents of new
 version prefixed with '+'.
 
 
 a complete rewrite by showing the entire contents of old version
 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
 
 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-*
+-S option and the `\--pickaxe-all` option to the git-diff-*

 commands.
 
 When diffcore-pickaxe is in use, it checks if there are
 commands.
 
 When diffcore-pickaxe is in use, it checks if there are


@@ -215,34 +240,36 @@ 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.
 
 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
-output.  When --pickaxe-all is used, diffcore-pickaxe leaves all
+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
 changeset easier.
 
 
 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
 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 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.
 
 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
-should look like this:
-
-    README
-    Makefile
-    Documentation
-    *.h
-    *.c
-    t
+As an example, a typical orderfile for the core git probably
+would look like this:
+
+------------------------------------------------
+README
+Makefile
+Documentation
+*.h
+*.c
+t
+------------------------------------------------