Ah yeah that would 100% accomplish the ask here!

In D25823#22324, @valerio.bozzolan wrote:

Hi @keithzg (and any SVN hacker) do you like the new added Subversion support?

In D25823#22043, @avivey wrote:

What if the user used the svn checkout svn+ssh://phab@phorge.example.com/source/myrepo/trunk myRepoOnlyTrunk form - are we still able to find the right target when arc browse lol.txt? Is it a common use-case?

For what it's worth I've applied this to my personal instance which tracks master, and I've foisted it on my work instance too---ostensibly tracking stable there, but ;)

Okay, I got it! For future reference if anyone in a similar situation is stumbling across this and wants a fully working example to go off of, my more-than-a-little-cargo-culted code is currently:

Many thanks, @20after4! That all largely did it; in addition to setting up the object a bit wrong (I knew it was a ManiphestTask instance, but was failing to get the actual object of it), I was also just using essentially my:custom-field rather than std:maniphest:my:custom-field.

Does appear fixed in latest master!

I saw that in my searching but I just end up with Argument 1 passed to PhabricatorCustomField::getObjectField() must implement interface PhabricatorCustomFieldInterface whenever I try to use it, perhaps because I'm unsure what to actually pass it as the $object other than $this, though I second-guess my second-guessing because ManifestCustomField, which I'm extending, does seem to have the interface the error is claiming I'm missing?