Merged hgitaly2 branch into default branch

This long-running named branch was to carry intrusive changes
necessary for operation without any auxiliary Git repository.

As of !65, we've reached the point were everything is neatly
separated and fully optional, depending on choices made by the
other Heptapod components.

I have checked as thoroughly as possible that using the `hgitaly2`
branch of py-heptapod didn't break anything (unit/integration tests,
functional tests).
5 jobs for !66 with topic/default/merge-hgitaly2 in 3 minutes and 30 seconds (queued for 3 seconds)
latest detached
Status Name Job ID Coverage
  Main
passed tests-current #254281

00:01:45

100.0%
 
  Compat
passed check-sdist #254282

00:02:15

failed tests-hg-default #254284
allowed to fail

00:01:38

99.0%
passed tests-hg-git-default #254285

00:01:40

100.0%
passed tests-hg-stable #254283

00:01:36

100.0%
 
Name Stage Failure
failed
tests-hg-default Compat
hgext3rd/heptapod/typed_ref.py                           35      0   100%
-------------------------------------------------------------------------
TOTAL 4507 2 99%

FAIL Required test coverage of 100% not reached. Total coverage: 99.96%
==================== 1 failed, 302 passed in 24.36 seconds =====================
Cleaning up file based variables
nothing to do
ERROR: Job failed: exit code 1