hooks: add some test about HGPLAIN setting and hooks...
hooks: add some test about HGPLAIN setting and hooks
In Mercurial 5.7, hooks are now ran with HGPLAIN set, which is a behavior change
in. I could not find explicit test about it so I am adding one. The next
changesets will introduce more change to help user mitigate the behavior change
when needed.
Differential Revision:
https://phab.mercurial-scm.org/D9979
