rhg: Add support for environment variables in config include paths Some tests rely on this. Differential Revision: https://phab.mercurial-scm.org/D10140

rhg: Add support for the HGRCSKIPREPO environment variable It’s easy enough and affects tests, well, that test that feature. Differential Revision: https://phab.mercurial-scm.org/D10139

rhg: Don’t make repository path absolute too early Some error messages want to include a relative path, which affects the output of some tests. Differential Revision: https://phab.mercurial-scm.org/D10138

rhg: Fall back to Python if ui.relative-paths is configured This feature is not supported yet, and affects the output of some tests. Differential Revision: https://phab.mercurial-scm.org/D10137

tests: clarify some missing output in test-merge-subrepos This makes the test behavior clearer, especially, why the output are inconsistent. Differential Revision: https://phab.mercurial-scm.org/D10136

tests: Adapt expected output for minor differences with rhg Differential Revision: https://phab.mercurial-scm.org/D10135

rhg: Add support for --cwd This affect the meaning of relative paths in `--repository`, which are resolved "early" by rhg in order to load config which is needed before fallback to Python is considered. An incorrect path could cause errors when loading a non-existent repo, leading to failing tests even when fallback is enabled. Differential Revision: https://phab.mercurial-scm.org/D10134

rhg: Align with Python on some more error messages Differences can cause some tests to fail Differential Revision: https://phab.mercurial-scm.org/D10133