Re: [PATCH] rebase -x: sanity check command

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Phillip,

On Mon, 28 Jan 2019, Phillip Wood wrote:

> From: Phillip Wood <phillip.wood@dunelm.org.uk>
> 
> If the user gives an empty argument to --exec then the rebase starts to
> run before erroring out with
> 
>   error: missing arguments for exec
>   error: invalid line 2: exec
>   You can fix this with 'git rebase --edit-todo' and then run 'git rebase --continue'.
>   Or you can abort the rebase with 'git rebase --abort'.

And that's the same if you specify an incorrect command.

In both cases, I would probably heed the second line of the advice: git
rebase --abort.

> Instead check for empty commands before starting the rebase.
> 
> Also check that the command does not contain any newlines as the
> todo-list format is unable to cope with multiline commands. Note that
> this changes the behavior, before this change one could do
> 
> git rebase --exec='echo one
> exec echo two'
> 
> and it would insert two exec lines in the todo list, now it will error
> out.

This, however, makes a ton of sense to me.

> diff --git a/builtin/rebase.c b/builtin/rebase.c
> index 00de70365e..b6c54b03c1 100644
> --- a/builtin/rebase.c
> +++ b/builtin/rebase.c
> @@ -793,6 +793,24 @@ static void set_reflog_action(struct rebase_options *options)
>  	strbuf_release(&buf);
>  }
>  
> +static int check_exec_cmd(const char *cmd)
> +{
> +	int non_blank = 0;
> +
> +	while (*cmd) {
> +		if (*cmd == '\n')
> +			return error(_("exec commands cannot contain newlines"));
> +		if (!isspace(*cmd))
> +			non_blank = 1;
> +		cmd++;
> +	}
> +
> +	if (non_blank)
> +		return 0;

We are not in a performance critical path here, so I would prefer the
readability of this code:

	if (strchr(cmd, '\n'))
		return error(...);

And if you *really* must,

	/* Does the command consist purely of whitespace? */
	if (!cmd[strspn(cmd, " \t\r\n")])
		return error(...);

But as I suggested also in a reply to Junio's answer: where would we stop
to validate the commands?

Ciao,
Dscho

> +
> +	return error(_("empty exec command"));
> +}
> +
>  int cmd_rebase(int argc, const char **argv, const char *prefix)
>  {
>  	struct rebase_options options = {
> @@ -1130,6 +1148,10 @@ 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");
>  
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 7a440e08d8..c98f64eb2d 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/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" &&
> -- 
> 2.20.1
> 
>