Merge branch 'pw/rebase-x-sanity-check'

"git rebase -x $cmd" did not reject multi-line command, even though
the command is incapable of handling such a command.  It now is
rejected upfront.

* pw/rebase-x-sanity-check:
  rebase -x: sanity check command

builtin/rebase.c

@@ -1005,6 +1005,19 @@ static void set_reflog_action(struct rebase_options *options)
 	strbuf_release(&buf);
 }
+static int check_exec_cmd(const char *cmd)
+{
+	if (strchr(cmd, '\n'))
+		return error(_("exec commands cannot contain newlines"));
+
+	/* Does the command consist purely of whitespace? */
+	if (!cmd[strspn(cmd, " \t\r\f\v")])
+		return error(_("empty exec command"));
+
+	return 0;
+}
+
+
 int cmd_rebase(int argc, const char **argv, const char *prefix)
 {
 	struct rebase_options options = {
@@ -1348,6 +1361,10 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		}
 	}
+	for (i = 0; i < exec.nr; i++)
+		if (check_exec_cmd(exec.items[i].string))
+			exit(1);
+
 	if (!(options.flags & REBASE_NO_QUIET))
 		argv_array_push(&options.git_am_opts, "-q");

t/t3404-rebase-interactive.sh

@@ -147,6 +147,25 @@ test_expect_success 'rebase -i with the exec command checks tree cleanness' '
 	git rebase --continue
 '
+test_expect_success 'rebase -x with empty command fails' '
+	test_when_finished "git rebase --abort ||:" &&
+	test_must_fail git rebase -x "" @ 2>actual &&
+	test_write_lines "error: empty exec command" >expected &&
+	test_i18ncmp expected actual &&
+	test_must_fail git rebase -x " " @ 2>actual &&
+	test_i18ncmp expected actual
+'
+
+LF='
+'
+test_expect_success 'rebase -x with newline in command fails' '
+	test_when_finished "git rebase --abort ||:" &&
+	test_must_fail git rebase -x "a${LF}b" @ 2>actual &&
+	test_write_lines "error: exec commands cannot contain newlines" \
+			 >expected &&
+	test_i18ncmp expected actual
+'
+
 test_expect_success 'rebase -i with exec of inexistent command' '
 	git checkout master &&
 	test_when_finished "git rebase --abort" &&