[PATCH] Add -B flag to diff-* brothers.

A new diffcore transformation, diffcore-break.c, is introduced.

When the -B flag is given, a patch that represents a complete
rewrite is broken into a deletion followed by a creation.  This
makes it easier to review such a complete rewrite patch.

The -B flag takes the same syntax as the -M and -C flags to
specify the minimum amount of non-source material the resulting
file needs to have to be considered a complete rewrite, and
defaults to 99% if not specified.

As the new test t4008-diff-break-rewrite.sh demonstrates, if a
file is a complete rewrite, it is broken into a delete/create
pair, which can further be subjected to the usual rename
detection if -M or -C is used.  For example, if file0 gets
completely rewritten to make it as if it were rather based on
file1 which itself disappeared, the following happens:

    The original change looks like this:

	file0     --> file0' (quite different from file0)
	file1     --> /dev/null

    After diffcore-break runs, it would become this:

	file0     --> /dev/null
	/dev/null --> file0'
	file1     --> /dev/null

    Then diffcore-rename matches them up:

	file1     --> file0'

The internal score values are finer grained now.  Earlier
maximum of 10000 has been raised to 60000; there is no user
visible changes but there is no reason to waste available bits.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/diff.h b/diff.h
index 00e46b544d..ef0dfe287a 100644
--- a/diff.h
+++ b/diff.h
@@ -43,9 +43,12 @@ extern void diffcore_pickaxe(const char *needle, int opts);
 
 extern void diffcore_pathspec(const char **pathspec);
 
+extern void diffcore_break(int);
+
 extern void diffcore_std(const char **paths,
 			 int detect_rename, int rename_score,
-			 const char *pickaxe, int pickaxe_opts);
+			 const char *pickaxe, int pickaxe_opts,
+			 int break_opt);
 
 extern int diff_queue_is_empty(void);