Defined Git constants

These are also implicitely part of the Gitaly protocol, and expected
by clients in various places.
2 jobs for !34 with topic/default/git-oids-constants in 37 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Compat
failed #167897
allowed to fail
tests-hg-default

00:00:21

passed #167896
tests-hg-stable

00:00:37

100.0%
 
Name Stage Failure
failed
tests-hg-default Compat
    writing top-level names to pip-egg-info/mercurial.egg-info/top_level.txt
writing manifest file 'pip-egg-info/mercurial.egg-info/SOURCES.txt'
Python headers are required to build Mercurial but weren't found in /usr/include/python3.7m/Python.h

----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-jy8cpum0/Mercurial/
Running after_script
Uploading artifacts for failed job
ERROR: Job failed: exit code 1