Make merge-recursive honor diff.renamelimit

It might be a sign of source code management gone bad, but when two branches
has diverged almost beyond recognition and time has come for the branches to
merge, the user is going to need all the help his tool can give him. Honoring
diff.renamelimit has great potential as a painkiller in such situations.

The painkiller effect could have been achieved by e.g. 'merge.renamelimit',
but the flexibility gained by a separate option is questionable: our user
would probably expect git to detect renames equally good when merging as
when diffing (I known I did).

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -96,6 +96,7 @@ static struct path_list current_directory_set = {NULL, 0, 0, 1};
 
 static int call_depth = 0;
 static int verbosity = 2;
+static int rename_limit = -1;
 static int buffer_output = 1;
 static struct output_buffer *output_list, *output_end;
 
@@ -372,6 +373,7 @@ static struct path_list *get_renames(struct tree *tree,
 	diff_setup(&opts);
 	opts.recursive = 1;
 	opts.detect_rename = DIFF_DETECT_RENAME;
+	opts.rename_limit = rename_limit;
 	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
 	if (diff_setup_done(&opts) < 0)
 		die("diff setup failed");
@@ -1693,6 +1695,10 @@ static int merge_config(const char *var, const char *value)
 		verbosity = git_config_int(var, value);
 		return 0;
 	}
+	if (!strcasecmp(var, "diff.renamelimit")) {
+		rename_limit = git_config_int(var, value);
+		return 0;
+	}
 	return git_default_config(var, value);
 }