Re: [PATCH v2 2/2] remote.c: fix handling of %(push:remoteref)

From: Damien Robert <damien.olivier.robert@gmail.com>
Date: Mar 3, 2020, 22:24 UTC
Message-ID: <20200303222423.wfbjuuwp3263qesv@doriath>
In-Reply-To: <xmqqtv358fkk.fsf@gitster-ct.c.googlers.com>

From Junio C Hamano, Tue 03 Mar 2020 at 10:21:31 (-0800) :

> Mental note: this function was moved down, the main part of the
> logic extracted to a new branch_get_push_remoteref() helper, which
> in addition got extended.

Exactly.

> That's a fairly expensive way to write
> 	if (remote->push.nr)
> 		return apply_refspecs(&remote->push, branch->refname);
> one-liner.

You anticipated the question I asked afterwards :)

Show 11 quoted lines

> > +	case PUSH_DEFAULT_UPSTREAM:
> > +		{
> > +			if (!branch || !branch->merge ||
> > +			    !branch->merge[0] || !branch->merge[0]->dst)
> > +			return NULL;
> > +
> > +			return branch->merge[0]->src;
> > +		}
> 
> This is strangely indented and somewhat unreadable.  Why isn't this
> more like:

Sorry I missed the indentation for the return NULL.

Show 8 quoted lines

> 	case PUSH_DEFAULT_UPSTREAM:
> 		if (branch && branch->merge && branch->merge[0] &&
> 		    branch->merge[0]->dst)
> 			return branch->merge[0]->src;
> 		break;
> 
> and have "return NULL" after the switch() statement before we leave
> the function?

We could, I agree this is more readable. If we return NULL after the switch, we need to put the

> > +	BUG("unhandled push situation")

in a default clause a you say.

The reason I wrote the code as above is to be as close as possible to `branch_get_push_1`. If we make the changes you suggest, I'll probably need a preliminary patch to change `branch_get_push_1` accordingly.

Show 20 quoted lines

> > +	case PUSH_DEFAULT_UNSPECIFIED:
> > +	case PUSH_DEFAULT_SIMPLE:
> > +		{
> > +			const char *up, *cur;
> > +
> > +			up = branch_get_upstream(branch, NULL);
> > +			if (!up)
> > +				return NULL;
> > +			cur = tracking_for_push_dest(remote, branch->refname, NULL);
> > +			if (!cur)
> > +				return NULL;
> > +			if (strcmp(cur, up))
> > +				return NULL;
> 
> This is probably not all that performance critical, so
> 			up = branch_get_upstream(branch, NULL);
> 			current = tracking_for_push_dest(remote, branch->refname, NULL);
> 			if (!up || !current || strcmp(current, up))
> 				return NULL;
> might be easier to follow.

I don't mind but likewise in this case we should probably change branch_get_push_1 too.

> By the way, I have a bit higher-level question.  
> 
> All of the above logic that decides what should happen in "git push"
> MUST have existing code we already use to implement "git push", no?

Yes.

> Why do we need to reinvent it here, instead of reusing the existing
> code?  Is it because the interface into the functions that implement
> the existing logic is very different from what this function wants?

Mostly yes. The logic of git push is to massage the refspecs directly, for
instance:
	case PUSH_DEFAULT_MATCHING:
		refspec_append(&rs, ":");
	case PUSH_DEFAULT_CURRENT:
		...
		strbuf_addf(&refspec, "%s:%s", branch->refname, branch->refname);
	case PUSH_DEFAULT_UPSTREAM:
		...
		strbuf_addf(&refspec, "%s:%s", branch->refname, branch->merge[0]->src);

And the error messages are also not the same, and to give a good error message we need to parse the different cases.

It may be possible to refactorize all this, but not in an obvious way and it would be a lot more work than this patch series.

-- 
Damien Robert
http://www.normalesup.org/~robert/pro