hghave: document format for version feature checks as <name><vers>, no dots
I had a bit of a difficult time when attempting to fix a use of `py-38` when
trying to figure out what the correct way of specifying the feature was. By
having the strings 'py-3*' and 'py3.8' in the hghave.checkvers docstring, I
would have had a much easier time of it instead of having to trace exactly what
was happening here.
Differential Revision: https://phab.mercurial-scm.org/D7023
running: init test1
result: 0
running: add foo
result: 0
running: commit -m commit1 -d 2000-01-01 foo
result: 0
running: commit -m commit2 -d 2000-01-02 foo
result: 0
running: log -r 0
changeset: 0:0e4634943879
user: test
date: Sat Jan 01 00:00:00 2000 +0000
summary: commit1
result: 0
running: log -r tip
changeset: 1:45589e459b2e
tag: tip
user: test
date: Sun Jan 02 00:00:00 2000 +0000
summary: commit2
result: 0