Re: [PATCH 4/4] describe/name-rev: tell name-rev to peel the incoming object to commit first

[Jeff King <peff@peff.net>]

On Sun, Jul 07, 2013 at 03:33:44PM -0700, Junio C Hamano wrote:

> With this on top of the other patches in this series, you would get:
> 
>     $ git describe --contains $(git rev-parse v1.8.3 v1.8.3^0)
>     v1.8.3
>     v1.8.3
> 
> while you can still differentiate tags and the commits they point at
> with:
> 
>     $ git name-rev --refs=tags/\* --name-only $(git rev-parse v1.8.3 v1.8.3^0)
>     v1.8.3
>     v1.8.3^0
> 
> The difference in these two behaviours is achieved by adding --peel-to-commit
> option to "name-rev" and using it when "describe" internally calls it.

I am somewhat mixed on this.

You are changing the default behavior of name-rev and adding a new
option to restore it, so I wonder who (if anyone) might be broken. The
documentation is now also out of date; not only does it not mention
"peel-to-commit", but it claims the argument to name-rev is a
committish, which is not really true without that option.

On the other hand, the new default behavior seems way more sane to me.
In general, I would expect name-rev to:

  1. Behave more or less the same between "git name-rev $sha1" and "echo
     $sha1 | git name-rev --stdin". Your patch improves that. Though I
     note that --peel-to-commit does not affect --stdin at all. Should
     it? And of course the two differ in that the command line will take
     any rev-parse expression, and --stdin only looks for full sha1s.

  2. If name-rev prints "$X $Y", I would expect "git rev-parse $X" to
     equal "git rev-parse $Y". With peeling, that is not the case, and
     you get the misleading example that Ram showed:

       $ git name-rev 8af0605
       8af0605 tags/v1.8.3^0

    or more obviously weird:

       $ git name-rev v1.8.3
       v1.8.3 tags/v1.8.3^0

So I think your series moves in a good direction, but I would just worry
that it is breaking backwards compatibility (but like I said, I am not
clear on who is affected and what it means for them).

-Peff