Re: [PATCH 8/8] t0012: test "-h" with builtins

[Jeff King <peff@peff.net>]

[+cc Siddharth, so quoting copiously]

On Tue, May 30, 2017 at 11:27:56AM -0400, Jeff King wrote:

> > Travis seems to be seeing the same failure.  Curiously, the topic by
> > itself passes for me; iow, pu fails, pu^2 doesn't fail.
> > 
> >     git.git/pu$ ./git rev-list -h
> >     BUG: environment.c:173: setup_git_env called without repository
> >     Aborted (core dumped)
> > 
> > Hmph...
> 
> Ah, OK, I can reproduce when merged with pu. Bisecting it was tricky.
> To see the problem, you need both my new test _and_ b1ef400ee
> (setup_git_env: avoid blind fall-back to ".git", 2016-10-20). The latter
> is only in v2.13, so topics forked from v2.12 need that commit applied.
> 
> Anyway, the problem is sk/dash-is-previous, specifically fc5684b47
> (revision.c: args starting with "-" might be a revision, 2017-02-25). It
> looks like the revision parser used to just bail on "-h", because
> revision.c would say "I don't recognize this" and then cmd_rev_list()
> would similarly say "I don't recognize this" and call usage(). But now
> we actually try to read it as a ref, which obviously requires being
> inside a repository.
> 
> Normally that's OK, but because of the "-h doesn't set up the repo"
> thing from 99caeed05, we may not have setup the repo, and so looking up
> refs is forbidden. The fix is probably to have revision.c explicitly
> recognize "-h" and bail on it as an unknown option (it can't handle
> the flag itself because only the caller knows the full usage()).
> 
> I do wonder, though, if there's any other downside to trying to look up
> other options as revisions (at least it wastes time doing nonsense
> revision lookups on options known only to cmd_rev_list()).  I'm not sure
> why that commit passes everything starting with a dash as a possible
> revision, rather than just "-".
> 
> I.e.:
> 
> diff --git a/revision.c b/revision.c
> index 5470c33ac..1e26c3951 100644
> --- a/revision.c
> +++ b/revision.c
> @@ -2233,7 +2233,14 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
>  			}
>  			if (opts < 0)
>  				exit(128);
> -			maybe_opt = 1;
> +			if (arg[1]) {
> +				/* arg is an unknown option */
> +				argv[left++] = arg;
> +				continue;
> +			} else {
> +				/* special token "-" */
> +				maybe_opt = 1;
> +			}
>  		}
>  
>  
> 
> I don't see anything in the commit message, but I didn't dig in the
> mailing list.

I think this line of reasoning comes from

  http://public-inbox.org/git/20170206181026.GA4010@ubuntu-512mb-blr1-01.localdomain/

And the idea is that ranges like "-.." should work. TBH, I'm not sure
how I feel about that, for exactly the reason that came up here: it
makes it hard to syntactically differentiate the "-" shorthand from
actual options. We do have @{-1} already for this purpose. I don't mind
"-" as a shortcut for things like "git checkout -" or "git show -", but
it feels like most of the benefit is lost when you're combining it with
other operators.

-Peff