blame: -C -C -C

When you do this, existing "blame -C -C" would not find that the
latter half of the file2 came from the existing file1:

	... both file1 and file2 are tracked ...
	$ cat file1 >>file2
	$ git add file1 file2
	$ git commit

This is because we avoid the expensive find-copies-harder code
that makes unchanged file (in this case, file1) as a candidate
for copy & paste source when annotating an existing file
(file2).  The third -C now allows it.  However, this obviously
makes the process very expensive.  We've actually seen this
patch before, but I dismissed it because it covers such a narrow
(and arguably stupid) corner case.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/builtin-blame.c b/builtin-blame.c
index f8843e6340acca5cb46d533135df440166b14293..65d029a773691f994711478bc2475681093e0088 100644 (file)
--- a/builtin-blame.c
+++ b/builtin-blame.c
@@ -55,6 +55,7 @@ static int num_commits;
 #define PICKAXE_BLAME_MOVE             01
 #define PICKAXE_BLAME_COPY             02
 #define PICKAXE_BLAME_COPY_HARDER      04
+#define PICKAXE_BLAME_COPY_HARDEST     010
 
 /*
  * blame for a blame_entry with score lower than these thresholds
@@ -1079,8 +1080,9 @@ static int find_copy_in_parent(struct scoreboard *sb,
         * and this code needs to be after diff_setup_done(), which
         * usually makes find-copies-harder imply copy detection.
         */
-       if ((opt & PICKAXE_BLAME_COPY_HARDER) &&
-           (!porigin || strcmp(target->path, porigin->path)))
+       if ((opt & PICKAXE_BLAME_COPY_HARDEST)
+           || ((opt & PICKAXE_BLAME_COPY_HARDER)
+               && (!porigin || strcmp(target->path, porigin->path))))
                diff_opts.find_copies_harder = 1;
 
        if (is_null_sha1(target->commit->object.sha1))
@@ -2127,6 +2129,15 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                        blame_move_score = parse_score(arg+2);
                }
                else if (!prefixcmp(arg, "-C")) {
+                       /*
+                        * -C enables copy from removed files;
+                        * -C -C enables copy from existing files, but only
+                        *       when blaming a new file;
+                        * -C -C -C enables copy from existing files for
+                        *          everybody
+                        */
+                       if (opt & PICKAXE_BLAME_COPY_HARDER)
+                               opt |= PICKAXE_BLAME_COPY_HARDEST;
                        if (opt & PICKAXE_BLAME_COPY)
                                opt |= PICKAXE_BLAME_COPY_HARDER;
                        opt |= PICKAXE_BLAME_COPY | PICKAXE_BLAME_MOVE;