Re: [RFC/PATCH] rebase: use reflog to find common base with upstream

[John Keeping <john@keeping.me.uk>]

On Mon, Dec 09, 2013 at 12:11:50PM -0800, Junio C Hamano wrote:
> John Keeping <john@keeping.me.uk> writes:
> 
> > Last time this came up [1], there was some discussion about moving the
> > added block of code to affect upstreams given on the command line as
> > well as when the upstream is discovered from the config.  Having tried
> > that, it has some more fallout on the test suite than I like; this
> > pattern ends up dropping the tip commit of "side" because it's in the
> > reflog of "master":
> >
> > 	# start on "master"
> > 	git branch side &&
> > 	git reset --hard HEAD^ &&
> > 	git checkout side &&
> > 	git rebase master
> 
> We shouldn't do anything funky using the reflog when an explicit
> commit object name was given like in the last step above, I think.
> Automation to help human end-users is good, but at some level there
> must be a mechanism to reliably reproduce the same result given the
> same precondition for those who implement such automation, and I do
> not think it is a good idea to force scripts to say
> 
> 	git rebase --do-not-look-at-reflog master
> 
> in order to do so.
> 
> > I wonder if it would be better to add a --fork-point argument to
> > git-rebase and default it to true when no upstream is given on the
> > command line.
> 
> I am not sure what you exactly mean by "when no upstream is given",
> though.  Do you mean
> 
> 	git rebase <no other arguments>
> 
> which we interpret as "rebase the current branch on @{u}", and it
> should behave as if the command was run like so:
> 
> 	git rebase --fork-point @{u}
> 
> If that is what you suggest, I certainly can buy that.  Those who
> want to disable the automation can explicitly say
> 
> 	git rebase @{u}
> 
> and rebase the current exactly on top of the named commit (e.g. the
> current value of refs/remotes/origin/master or whatever remote-tracking
> branch you forked from).

Yes, that's what I meant; the first non-option argument to "git rebase"
is called "upstream" in the manpage (and throughout the code).  So if
"<no other arguments>" means "<no non-option arguments>" then that's
exactly what I meant.