Oldest supported version of Mercurial?

[mark.reinhold at oracle.com]

I'm working to upgrade the trees extension to run on the latest version
of Mercurial (4.5).

We've accumulated a number of hacky workarounds to support older
versions, all the way back to Mercurial 1.1, and more such hacks would
be needed to cope with recent (>= 4.2) changes to Mercurial's internal
API.

Is it time to drop some of these older workarounds?  Would it be okay
for the trees extension (and possibly others) only to work with, say,
Mercurial 2.2 and later?  (2.2 shipped on 2012/5/1, almost six years
ago.)

- Mark