tests/revnamesext.py

run-tests: rely on an actual executable in PATH instead of alias for `hg`

The alias approach is poorly inherited by other process that the test might
spawn.

To solve this we use the same approach as for `python`/`python3` we write an
executable file explicitly. Doing this fixes `which hg` invocation that now
returns the same location as `hg`.

Using chg server side has some minor effect on some stdout/stderr ordering when
using `chg` as the server too.

Differential Revision: https://phab.mercurial-scm.org/D11053

# Dummy extension to define a namespace containing revision names

from __future__ import absolute_import

from mercurial import namespaces


def reposetup(ui, repo):
    names = {b'r%d' % rev: repo[rev].node() for rev in repo}
    namemap = lambda r, name: names.get(name)
    nodemap = lambda r, node: [b'r%d' % repo[node].rev()]

    ns = namespaces.namespace(
        b'revnames',
        templatename=b'revname',
        logname=b'revname',
        listnames=lambda r: names.keys(),
        namemap=namemap,
        nodemap=nodemap,
    )
    repo.names.addnamespace(ns)