Re: [PATCH v6 1/3] branch: accept multiple upstream branches for tracking

[Glen Choo <chooglen@google.com>]

Josh Steadmon <steadmon@google.com> writes:

>> > @@ -87,29 +112,42 @@ int install_branch_config(int flag, const char *local, const char *origin, const
>> >  	strbuf_release(&key);
>> >  
>> >  	if (flag & BRANCH_CONFIG_VERBOSE) {
>> > -		if (shortname) {
>> > +		const char *name;
>> > +		struct strbuf ref_string = STRBUF_INIT;
>> > +
>> > +		for_each_string_list_item(item, remotes) {
>> > +			name = item->string;
>> > +			skip_prefix(name, "refs/heads/", &name);
>> > +			strbuf_addf(&ref_string, "  %s\n", name);
>> > +		}
>> > +
>> > +		if (remotes->nr == 1) {
>> > +			struct strbuf refname = STRBUF_INIT;
>> > +
>> >  			if (origin)
>> > -				printf_ln(rebasing ?
>> > -					  _("Branch '%s' set up to track remote branch '%s' from '%s' by rebasing.") :
>> > -					  _("Branch '%s' set up to track remote branch '%s' from '%s'."),
>> > -					  local, shortname, origin);
>> > -			else
>> > -				printf_ln(rebasing ?
>> > -					  _("Branch '%s' set up to track local branch '%s' by rebasing.") :
>> > -					  _("Branch '%s' set up to track local branch '%s'."),
>> > -					  local, shortname);
>> > +				strbuf_addf(&refname, "%s/", origin);
>> > +			strbuf_addstr(&refname, remotes->items[0].string);
>> > +
>> > +			/*
>> > +			 * Rebasing is only allowed in the case of a single
>> > +			 * upstream branch.
>> > +			 */
>> > +			printf_ln(rebasing ?
>> > +				_("branch '%s' set up to track '%s' by rebasing.") :
>> > +				_("branch '%s' set up to track '%s'."),
>> > +				local, refname.buf);
>> > +
>> > +			strbuf_release(&refname);
>> > +		} else if (origin) {
>> > +			printf_ln(_("branch '%s' set up to track from '%s':"),
>> > +				local, origin);
>> > +			printf("%s", ref_string.buf);
>> 
>> It's not clear to me why the hint contains the word 'from' when it is a
>> remote ref...
>
> Because in the multiple-branch case, we don't prepend the origin to each
> ref, so we need to let users know which remote the refs are coming from.

I see. So if I'm reading this correctly, the error message in the remote
case would read something like:

  branch 'main' set up to track from 'origin':
    main
    topic1
    topic2

Is there any reason why we couldn't append the origin to the ref to make
it consistent? I think this could be as simple as:


	for_each_string_list_item(item, remotes) {
		name = item->string;
		skip_prefix(name, "refs/heads/", &name);
			if (origin)
+         strbuf_addf(&ref_string, "%s/", origin);
		strbuf_addf(&ref_string, "  %s\n", name);
	}

and the resulting list could look like:

  branch 'main' set up to track from 'origin':
    origin/main
    origin/topic1
    origin/topic2

This looks repetitive, but I suggest this because, as I understand it,
we are omitting the "{local,remote} ref" phrase based on conventions
around ref names, like "origin/main" is probably a remote ref and not an
oddly named local ref. However, when we print the list like so,

  branch 'main' set up to track from 'origin':
    main
    topic1
    topic2

we now expect the user to understand that 'main', 'topic1' and 'topic2'
to implicitly have 'origin/' prepended to them. This behavior seems
inconsistent to me; I'd anticipate most users responding "Wait, I was
supposed to be tracking 'origin' branches right? Why am I looking at
local branches?". Some users would be able to recover because they can
figure out what we mean, but others might just give up.

Prepending 'origin/' would get rid of this problem altogether, and it
would let us drop the 'from'.

>> >  		} else {
>> > -			if (origin)
>> > -				printf_ln(rebasing ?
>> > -					  _("Branch '%s' set up to track remote ref '%s' by rebasing.") :
>> > -					  _("Branch '%s' set up to track remote ref '%s'."),
>> > -					  local, remote);
>> > -			else
>> > -				printf_ln(rebasing ?
>> > -					  _("Branch '%s' set up to track local ref '%s' by rebasing.") :
>> > -					  _("Branch '%s' set up to track local ref '%s'."),
>> > -					  local, remote);
>> > +			printf_ln(_("branch '%s' set up to track:"), local);
>> > +			printf("%s", ref_string.buf);
>> 
>> but does not have the word 'from' when it is a local ref. As far as I
>> can tell, this is the only difference between remote and local refs, and
>> adding the word 'from' does not seem like a good enough reason to add an
>> 'if' condition. Maybe I missed something here?
>> 
>> This motivates my answer to the question you asked in [1]:
>> 
>>   I removed as many distinctions as possible, as most can still be
>>   inferred from context. [...] Likewise, we don't need to specify whether
>>   refs are remote or local: "some-remote/some-branch" vs.
>>   "a-local-branch" should be understandable without us spelling it out.
>> 
>> I agree that there is adequate context, so I would be ok with the
>> simplification if there was corresponding code simplification e.g.
>> dropping "if (origin)". But in its current form, I don't think there is
>> good enough reason to simplify the message.
>
> I think the proper point of comparison is not the original code, but the
> code from V5 where we try to preserve the same level of detail in output
> as the original code. If we are committed to both having multiple
> remotes and keeping similar styles of output as the original
> implementation, then something like the massive conditional in V5 is
> unavoidable.

I see. So for instance, post-simplification you have:

  printf_ln(rebasing ?
    _("branch '%s' set up to track '%s' by rebasing.") :
    _("branch '%s' set up to track '%s'."),
    local, refname.buf);

if you preserve the same amount of detail as before, you'd have to
distinguish between local/remote, which doubles the number of cases to
4, which is why the conditional v5 is so complicated.

That said, I think that it's already much simpler than v5 because you've
split the singular and plural cases. I wonder if you have considered
building the final string purely from format strings, like:

  char *message_format = _("branch %s set up to track %s%s%s%s");
  char *ref_type_clause = origin ? " remote ref " : " local ref ";
  char *rebasing_clause = rebasing ? " by rebasing." : ".";
  char *branch_names = "<branch names>";
  printf_ln(message_format, local, ref_type_clause, branch_names, rebasing_clause);

This sounds potentially unfriendly to i18n, but it would make the
conditional simpler. What do you think?