shortlog: extract `shortlog_finish_setup()`

Extract a function which finishes setting up the shortlog struct for
use. The caller in `make_cover_letter()` does not care about trailer
sorting, so it isn't strictly necessary to add a call there in this
patch.

But the next patch will add additional functionality to the new
`shortlog_finish_setup()` function, which the caller in
`make_cover_letter()` will care about.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/log.c

@@ -1334,6 +1334,7 @@ static void make_cover_letter(struct rev_info *rev, int use_separate_file,
 	log.in2 = 4;
 	log.file = rev->diffopt.file;
 	log.groups = SHORTLOG_GROUP_AUTHOR;
+	shortlog_finish_setup(&log);
 	for (i = 0; i < nr; i++)
 		shortlog_add_commit(&log, list[i]);
 

builtin/shortlog.c

@@ -381,6 +381,11 @@ void shortlog_init(struct shortlog *log)
 	log->format.strdup_strings = 1;
 }
 
+void shortlog_finish_setup(struct shortlog *log)
+{
+	string_list_sort(&log->trailers);
+}
+
 int cmd_shortlog(int argc, const char **argv, const char *prefix)
 {
 	struct shortlog log = { STRING_LIST_INIT_NODUP };
@@ -450,7 +455,7 @@ parse_done:
 
 	if (!log.groups)
 		log.groups = SHORTLOG_GROUP_AUTHOR;
-	string_list_sort(&log.trailers);
+	shortlog_finish_setup(&log);
 
 	/* assume HEAD if from a tty */
 	if (!nongit && !rev.pending.nr && isatty(0))

shortlog.h

@@ -33,6 +33,7 @@ struct shortlog {
 };
 
 void shortlog_init(struct shortlog *log);
+void shortlog_finish_setup(struct shortlog *log);
 
 void shortlog_add_commit(struct shortlog *log, struct commit *commit);