Re: [RFC/largely untested/PATCH] sha1_name: interpret ~n as HEAD~n

[Jeff King <peff@peff.net>]

On Fri, Apr 29, 2011 at 05:53:15PM +0200, Michael J Gruber wrote:

> HEAD~n is often used for rebase invocations etc. Make it use the same
> default we use in other places, i.e. ~n == HEAD~n.

Hmm. It certainly makes sense in that we often default emptiness to
HEAD, but I don't think we can extend this syntax to other things. For
example, seeing ~n makes me think that ^n or ^{tree} would work. But of
course "^" at the beginning of a ref means something completely
different. So it's not completely consistent.

Consistency-wise, I'm not sure if it makes things better or worse.
Obviously we have "foo.." with an implicit HEAD. You could argue that
".." is a different operator altogether, and that any operator that is a
"ref modifier" like "~" or "^" needs to have a non-implicit ref. But
that gets muddier with "@{4.hours.ago}", which also takes an implicit
value, except that it isn't exactly HEAD. It's the branch pointed to by
HEAD.

So there really isn't a lot of consistency, I guess.  It also conflicts
a little with the shell's "~user" syntax, though presumably you don't
have users named "1" and "2".

-Peff