Re: default behaviour for `gitmerge` (no arguments)

[Junio C Hamano <gitster@pobox.com>]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

>> I wondered why it doesn't hook into interpret_branch_name(), and instead 
>> adds itself to the static substitute_branch_name(); it forbids the use 
>> of the syntax from by callers of strbuf_branchname().
>
> I _think_ it was to allow something like
>
> 	git log -g @{u}
>
> but frankly, this is so long ago, I do not remember, I reconstructed this 
> reasoning as being the most likely.

That is not the question I was asking.

If you compare substitute_branch_name() and interpret_branch_name() before
your patch, you will notice that they are _meant_ to do the same thing,
with different external API, only because many callers in sha1_name.c do
not use strbuf to hold their names.  The primary API is the latter (which
is extern), and the former (which is static) is merely a helping wrapper
that is internal to sha1_name.c

But with your patch, they suddenly have different semantics, and the
function that implements the primary API doesn't know anything about
this new @{upstream} syntax.

This discrepancy will affect callers of strbuf_branchname(), e.g.
merge_name() in builtin-merge.c that prepares the "Merge branch nitfol of
remote frotz" message, or delete_branches() in builtin-branch.c.

Note that I am not saying "branch -d @{upstream}" should or should not
work (at least not yet---I haven't thought the issues through).  But I
wanted to know if this subtle change in the semantics was a deliberate
choice, and if so wanted to see the reason behind it described clearly.