sha1-file: release strbuf after use

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/sha1-file.c b/sha1-file.c
index 84fd02f..487ea35 100644
--- a/sha1-file.c
+++ b/sha1-file.c
@@ -799,6 +799,7 @@
 
 	fclose(fh);
 	finish_command(&cmd);
+	strbuf_release(&line);
 }
 
 struct alternate_refs_data {