D1962: setdiscovery: don't call "heads" wire command when heads specified

[indygreg (Gregory Szorc)]

indygreg accepted this revision.
indygreg added a comment.
This revision is now accepted and ready to land.


  I initially thought this would have test fallout. But since we're using a batch command to issue the `heads` wire protocol command, it won't show up in HTTP logs. We'd only catch it in verbose/debug logging, which we don't do a lot of. So no test fallout is expected.
  
  FWIW, while computing DAG heads is probably cheap, sending them over the wire may not be. 41 bytes per head can add up pretty quickly and turn what would be a <1kb response into several kb.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D1962

To: martinvonz, #hg-reviewers, indygreg
Cc: indygreg, mercurial-devel