merge-recursive: option to specify rename threshold

The recursive merge strategy turns on rename detection but leaves the
rename threshold at the default. Add a strategy option to allow the user
to specify a rename threshold to use.

Signed-off-by: Kevin Ballard <kevin@sb.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/merge-strategies.txt

@@ -74,6 +74,10 @@ no-renormalize;;
 	Disables the `renormalize` option.  This overrides the
 	`merge.renormalize` configuration variable.
 
+rename-threshold=<n>;;
+	Controls the similarity threshold used for rename detection.
+	See also linkgit:git-diff[1] `-M`.
+
 subtree[=path];;
 	This option is a more advanced form of 'subtree' strategy, where
 	the strategy makes a guess on how two trees must be shifted to

diff.c

@@ -3219,7 +3219,7 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	return 1;
 }
 
-static int parse_num(const char **cp_p)
+int parse_rename_score(const char **cp_p)
 {
 	unsigned long num, scale;
 	int ch, dot;
@@ -3265,7 +3265,7 @@ static int diff_scoreopt_parse(const char *opt)
 	if (cmd != 'M' && cmd != 'C' && cmd != 'B')
 		return -1; /* that is not a -M, -C nor -B option */
 
-	opt1 = parse_num(&opt);
+	opt1 = parse_rename_score(&opt);
 	if (cmd != 'B')
 		opt2 = 0;
 	else {
@@ -3275,7 +3275,7 @@ static int diff_scoreopt_parse(const char *opt)
 			return -1; /* we expect -B80/99 or -B80 */
 		else {
 			opt++;
-			opt2 = parse_num(&opt);
+			opt2 = parse_rename_score(&opt);
 		}
 	}
 	if (*opt != 0)

diff.h

@@ -301,4 +301,6 @@ extern size_t fill_textconv(struct userdiff_driver *driver,
 
 extern struct userdiff_driver *get_textconv(struct diff_filespec *one);
 
+extern int parse_rename_score(const char **cp_p);
+
 #endif /* DIFF_H */

merge-recursive.c

@@ -339,6 +339,7 @@ static struct string_list *get_renames(struct merge_options *o,
 	opts.rename_limit = o->merge_rename_limit >= 0 ? o->merge_rename_limit :
 			    o->diff_rename_limit >= 0 ? o->diff_rename_limit :
 			    500;
+	opts.rename_score = o->rename_score;
 	opts.warn_on_too_large_rename = 1;
 	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
 	if (diff_setup_done(&opts) < 0)
@@ -1525,6 +1526,11 @@ int parse_merge_opt(struct merge_options *o, const char *s)
 		o->renormalize = 1;
 	else if (!strcmp(s, "no-renormalize"))
 		o->renormalize = 0;
+	else if (!prefixcmp(s, "rename-threshold=")) {
+		const char *score = s + strlen("rename-threshold=");
+		if ((o->rename_score = parse_rename_score(&score)) == -1 || *score != 0)
+			return -1;
+	}
 	else
 		return -1;
 	return 0;

merge-recursive.h

@@ -19,6 +19,7 @@ struct merge_options {
 	int verbosity;
 	int diff_rename_limit;
 	int merge_rename_limit;
+	int rename_score;
 	int call_depth;
 	struct strbuf obuf;
 	struct string_list current_file_set;