Answer by DustWolf for Not trusting file .hg/hgrc from untrusted user root, group dev

For everybody else who has added this solution to their /repo/.hg/hgrc and nothing happened, this solution worked for me:https://j.ee.washington.edu/trac/gmtk/ticket/33

Add in /etc/mercurial/hgrc.d/trust.rc

[trusted]groups = yourgroupusers = youruser

Essentially, writing permissions to /repo/.hg/hgrc will not work, because the file itself is owned by an untrusted user.