Summary:

Use bundle.mainreporoot as "hg root"

Review Request #11146 — Created Aug. 20, 2020 and submitted Aug. 20, 2020, 3:16 p.m.

Description

This saves one more hg binary call and replaces
"hg root" with the value of "bundle.mainreporoot" of
"hg showconfig" as it is the same.

Testing Done

Checked the debug outpot of rbt post that
it do not call hg root and uses the correct path.

flake8 passed.

JSHint passed.

-	a905c3c1cbeca5d9d66a92e2d2cf6edbe9c23916
+	2f303b715e3a8649c4a2be6305cfad4c3fe908c1

flake8 passed.

JSHint passed.

Ship it!

Pushed to release-2.0.x (88f968f)