Re: Fwd: Errors when diff'ing arbitrary upstream remotes are not intuitive if git pull --all hasn't been done

From: Johan Herland <johan@herland.net>
Date: Oct 25, 2013, 07:03 UTC
Message-ID: <CALKQrgc0u8TA4mXc+2Hv+Fyo8EYNuiickF_janeCxkzFn+xAvA@mail.gmail.com>
In-Reply-To: <20131025061459.GA23524@sigill.intra.peff.net>

On Fri, Oct 25, 2013 at 8:14 AM, Jeff King <peff@peff.net> wrote:

Show 18 quoted lines

> On Fri, Oct 25, 2013 at 02:14:07AM -0400, Jeff King wrote:
>> >     Could this error message be improved for interactive commands by
>> > first checking to see whether or not the path starts with a remote,
>> > then recommend that the remote be pulled?
>>
>> That might be worth doing. We cannot definitely say the branch exists
>> without hitting the network (which we would not want to do in the
>> general case), but I think it is reasonable for git to give suggestions
>> (we could also give a "did you mean X..." for near-typos, as we do for
>> typo-ed commands like "git dif".
>>
>> If you do try it, please don't just check for the remote name, but
>> actually complete the right-hand side of the fetch refspec for each
>> remote. They are equivalent in the default config, but aren't
>> necessarily so (and there has been talk of adjusting the layout of
>> remote refspecs). I don't recall offhand what functions we have to help
>> you, but I believe Johan (cc'd) was working in this area recently and
>> might be able to say more.

Actually, I don't think there's much refspec stuff to be done here. When running "git diff $remote/$branch", there are 3 possible outcomes:

 - $remote is not a valid remote name, the user probably meant
something different (like "nested/branch"). The current error message
is fine.

 - $remote is a valid remote name, but $branch has not (yet) been
fetched from there. Suggest the user run "git fetch $remote"

 - $remote/$branch is a valid remote-tracking branch. The diff works! No errors.

So, AFAICS, the patch should simply:

 1. Split the input on the first '/' into $remote/$branch, and use the
preceding part ($remote) as a potential remote name, and the following
part ($branch) as a potential branch name. (Although it is
theoretically possible to have remote names containing slashes, I
don't think anybody uses them, and we have considered disallowing
them, mainly because of this very issue: it makes "$remote/$branch"
parsing (even more) ambiguous)

 2. See if a remote called $remote exists. If it does, suggest to the
user to run "git fetch $remote". If $remote does not exist, leave the
current error message in place.

Hope this helps,

...Johan

-- 
Johan Herland, <johan@herland.net>
www.herland.net