Re: [PATCH 5/7] grep: fix "--" rev/pathspec disambiguation

> If we see "git grep pattern rev -- file" then we apply the
> usual rev/pathspec disambiguation rules: any "rev" before
> the "--" must be a revision, and we do not need to apply the
> verify_non_filename() check.
>
> But there are two bugs here:
>
>   1. We keep a seen_dashdash flag to handle this case, but
>      we set it in the same left-to-right pass over the
>      arguments in which we parse "rev".
>
>      So when we see "rev", we do not yet know that there is
>      a "--", and we mistakenly complain if there is a
>      matching file.
>
>      We can fix this by making a preliminary pass over the
>      arguments to find the "--", and only then checking the rev
>      arguments.
>
>   2. If we can't resolve "rev" but there isn't a dashdash,
>      that's OK. We treat it like a path, and complain later
>      if it doesn't exist.
>
>      But if there _is_ a dashdash, then we know it must be a
>      rev, and should treat it as such, complaining if it
>      does not resolve. The current code instead ignores it
>      and tries to treat it like a path.
>
> This patch fixes both bugs, and tries to comment the parsing
> flow a bit better.