reflog: fix 'show' subcommand's argv

cmd_reflog() invokes parse_options() with PARSE_OPT_KEEP_ARGV0, but it
doesn't account for the retained argv[0] before invoking
cmd_reflog_show() to handle the 'git reflog show' subcommand.
Consequently, cmd_reflog_show() always gets an 'argv' array starting
with elements argv[0]="reflog" and argv[1]="show".

Strip the name of the git command from the 'argv' array before passing
it to the function handling the 'show' subcommand.

There is no user-visible bug here, because cmd_reflog_show() doesn't
have any options or parameters of its own.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reflog.c

@@ -225,7 +225,7 @@ static int cmd_reflog_show(int argc, const char **argv, const char *prefix)
 		      PARSE_OPT_KEEP_DASHDASH | PARSE_OPT_KEEP_ARGV0 |
 		      PARSE_OPT_KEEP_UNKNOWN);
 
-	return cmd_log_reflog(argc - 1, argv + 1, prefix);
+	return cmd_log_reflog(argc, argv, prefix);
 }
 
 static int cmd_reflog_expire(int argc, const char **argv, const char *prefix)
@@ -425,7 +425,7 @@ int cmd_reflog(int argc, const char **argv, const char *prefix)
 		goto log_reflog;
 
 	if (!strcmp(argv[1], "show"))
-		return cmd_reflog_show(argc, argv, prefix);
+		return cmd_reflog_show(argc - 1, argv + 1, prefix);
 	else if (!strcmp(argv[1], "expire"))
 		return cmd_reflog_expire(argc - 1, argv + 1, prefix);
 	else if (!strcmp(argv[1], "delete"))