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

John Keeping [off-list ref] writes:

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".

Not quite, I am afraid.  Branch names used for "git branch <name>"
and "git checkout <name>" are like the Lvalue of an assignment, as
opposed to extended SHA-1 expressions to express any commit
(e.g. 'master^0', 'refs/heads/master', or 'master') that correspond
to the Rvalues used in an expression.  Because "git checkout" can
take a branch name or an arbitrary commit object name, there needs a
way for the users to disambiguate.

Saying that "git checkout refs/heads/name" must be equivalent to
"git checkout name" is like arguing that assignment "value+0 = x"
should be valid because "value+0" is a valid value.

For the first parameter to "git branch", there is no ambiguity---it
must be the name of a branch and cannot be an arbitrary commit
object name, so special casing "git branch refs/heads/master" to
mean "git branch master" may not be too bad.  But then we need to
either start rejecting "git branch refs/tags/v1.0" or keep allowing
it to create a ref refs/heads/refs/tags/v1.0 to denote the branch of
that exact name given---neither of which is more consistent, so...