get_patch_filename(): simplify function signature

Most functions that emit to a strbuf take the strbuf as their first
parameter; make this function follow suit.

The serial number of the patch being emitted (nr) and suffix used
for patch filename (suffix) are both recorded in rev_info; drop
these separate parameters and pass the rev_info directly.

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

builtin/log.c

@@ -684,7 +684,7 @@ static int reopen_stdout(struct commit *commit, const char *subject,
 			strbuf_addch(&filename, '/');
 	}
 
-	get_patch_filename(commit, subject, rev->nr, rev->patch_suffix, &filename);
+	get_patch_filename(&filename, commit, subject, rev);
 
 	if (!quiet)
 		fprintf(realstdout, "%s\n", filename.buf + outdir_offset);