D2608: templater: add hint to template parse errors to help locate issues

[pulkit (Pulkit Goyal)]

pulkit added a comment.


  I like similar things in rust too. I am +1 on this.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D2608

To: ryanmce, #hg-reviewers, durin42
Cc: pulkit, durin42, mercurial-devel