Re: error: src refspec refs/heads/master matches more than one.

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

On Tue, Feb 18, 2014 at 11:03:10AM -0800, Junio C Hamano wrote:
> Duy Nguyen <pclouds@gmail.com> writes:
> 
> > Prevent is a strong word. I meant we only do it if they force
> > it. Something like this..
> >
> > -- 8< --
> > diff --git a/branch.c b/branch.c
> > index 723a36b..3f0540f 100644
> > --- a/branch.c
> > +++ b/branch.c
> > @@ -251,6 +251,11 @@ void create_branch(const char *head,
> >  			forcing = 1;
> >  	}
> >  
> > +	if (!force && dwim_ref(name, strlen(name), sha1, &real_ref))
> > +		die(_("creating ref refs/heads/%s makes %s ambiguous.\n"
> > +		      "Use -f to create it anyway."),
> > +		    name, name);
> 
> Does this check still allow you to create a branch "refs/heads/next"
> and then later create a branch "next"?  The latter will introduce an
> ambiguity without any prevention, even though the prevention would
> trigger if the order in which these two branches are created is
> swapped--- the end result has ambiguity but the safety covers only
> one avenue to the confusing situation.
> 
> And the only way I can think of to avoid that kind of confusion is
> to forbid creation of a subset of possible names by reserving a set
> of known (but arbitrary) prefixes---which I am not sure is a good
> way to go.  At least not yet.

There's already the arbitrary set of prefixes in
refs.c::prettify_refname() and refs.c::ref_rev_parse_rules().  I can see
how a user might think that since "git log refs/heads/name" is
equivalent to "git log master" then "git branch refs/heads/name" should
be equivalent to "git branch name".

I don't think requiring "--force" for these branch names that overlap
with these special namespaces is a big leap from supporting them for
inspection commands.  Although I'm not sure how sensible it is to
examine every remote name to catch something like "git branch
origin/master".  Perhaps Duy's ambiguity check is the best thing for
that case.