blame: pay attention to --no-follow

If you know your history did not have renames, or if you care only
about the history after a large rename that happened some time ago,
"git blame --no-follow $path" is a way to tell the command not to
bother about renames.

When you use -C, the lines that came from the renamed file will
still be found without the whole-file rename detection, so it is not
all that interesting either way, though.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/blame.c

@@ -42,6 +42,7 @@ static int blank_boundary;
 static int incremental;
 static int xdl_opts;
 static int abbrev = -1;
+static int no_whole_file_rename;
 
 static enum date_mode blame_date_mode = DATE_ISO8601;
 static size_t blame_date_width;
@@ -1226,7 +1227,7 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
 	 * The first pass looks for unrenamed path to optimize for
 	 * common cases, then we look for renames in the second pass.
 	 */
-	for (pass = 0; pass < 2; pass++) {
+	for (pass = 0; pass < 2 - no_whole_file_rename; pass++) {
 		struct origin *(*find)(struct scoreboard *,
 				       struct commit *, struct origin *);
 		find = pass ? find_rename : find_origin;
@@ -2344,6 +2345,7 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 	init_revisions(&revs, NULL);
 	revs.date_mode = blame_date_mode;
 	DIFF_OPT_SET(&revs.diffopt, ALLOW_TEXTCONV);
+	DIFF_OPT_SET(&revs.diffopt, FOLLOW_RENAMES);
 
 	save_commit_buffer = 0;
 	dashdash_pos = 0;
@@ -2367,6 +2369,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 		parse_revision_opt(&revs, &ctx, options, blame_opt_usage);
 	}
 parse_done:
+	no_whole_file_rename = !DIFF_OPT_TST(&revs.diffopt, FOLLOW_RENAMES);
+	DIFF_OPT_CLR(&revs.diffopt, FOLLOW_RENAMES);
 	argc = parse_options_end(&ctx);
 
 	if (0 < abbrev)