Add a visual indication of opening a 3rd-party merge tool during Merge
Created originally on Bitbucket by edbrannin (Ed Brannin)
When I'm doing a Merge, sometimes I don't notice my external merge tool when it opens on another monitor. I often just see the Merge dialog appear to stop progressing, and wonder what's taking so long.
It would be nice if there were some indication in the Merge window that it's waiting for a third-party merge tool to close.
(I expect this may need to take the form of a Mercurial plugin or external-merge-tool hack.)