shortlog: respect the --output=<file> setting

Thanks to the diff option parsing, we already know about this option.
We just have to make use of it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/shortlog.c

@@ -229,7 +229,6 @@ void shortlog_init(struct shortlog *log)
 	log->wrap = DEFAULT_WRAPLEN;
 	log->in1 = DEFAULT_INDENT1;
 	log->in2 = DEFAULT_INDENT2;
-	log->file = stdout;
 }
 
 int cmd_shortlog(int argc, const char **argv, const char *prefix)
@@ -277,6 +276,7 @@ parse_done:
 
 	log.user_format = rev.commit_format == CMIT_FMT_USERFORMAT;
 	log.abbrev = rev.abbrev;
+	log.file = rev.diffopt.file;
 
 	/* assume HEAD if from a tty */
 	if (!nongit && !rev.pending.nr && isatty(0))
@@ -290,6 +290,8 @@ parse_done:
 		get_from_rev(&rev, &log);
 
 	shortlog_output(&log);
+	if (log.file != stdout)
+		fclose(log.file);
 	return 0;
 }
 

t/t4201-shortlog.sh

@@ -184,4 +184,10 @@ test_expect_success 'shortlog with revision pseudo options' '
 	git shortlog --exclude=refs/heads/m* --all
 '
 
+test_expect_success 'shortlog with --output=<file>' '
+	git shortlog --output=shortlog master >output &&
+	test ! -s output &&
+	test_line_count = 7 shortlog
+'
+
 test_done