Re: FETCH_HEAD question

Hi,

On Tue, 17 Feb 2009, Jay Soffian wrote:

On Tue, Feb 17, 2009 at 3:35 AM, Junio C Hamano [off-list ref] wrote:

quoted

Now to something totally useless.

After reading the builtin-merge.c and original git-merge.sh (now in
contrib/examples) script, I think it could have done something entirely
different.

It could have done this instead.

       sed -e '/       not-for-merge   /d'

to learn the commits and their human-readable origins, and it could have
tried to reproduce what "git pull" did when it invoked git-merge using
that information.  Then you could use this workflow:

       $ git pull <possibly with arguments>
       ... oops, conflicted and is very messy.
       ... I tried to resolve, but failed and made the mess even worse.
       ... Let's start over.
       $ git reset --hard
       ... FETCH_HEAD knows which refs are for merging
       $ git merge FETCH_HEAD

That is, no matter what the arguments were for the initial "git pull",
what should be merged is recorded in FETCH_HEAD, and that is how you can
retry the merge without refetching over the network.

But such a change makes FETCH_HEAD different from what it traditionally
meant, and does that only to "git merge", making the result very
inconsistent.  For example, "git log ..FETCH_HEAD" will still use the
object name on the first line, and it won't be a way to convince yourself
that the changes are sensible and it is Ok to run "git merge FETCH_HEAD"
anymore.  So I do not think such a change will be an improvement.

Unless dwim_ref() is updated to handle FETCH_HEAD specially, and
return not the first SHA1, but the one not marked "not-for-merge".
Then the UI would at least be consistent, but this would not be
backward compatible.

You cannot fix parsing FETCH_HEAD as a ref (and neither will you be able 
to do with PUSH_HEAD), as it can contain _more_ than one SHA-1s.  This 
still holds true when ignoring the not-for-merge lines, as an octopus is
a quite real possibility.

Ciao,
Dscho