rhg: Return an error code for `rhg config Section.idontexist` This is what Python-based hg does. Differential Revision: https://phab.mercurial-scm.org/D10145

rhg: Fall back to Python for --version Clap has some built-in support for printing something on --version, but it looks different than what Pytho-based hg does. Also, at the moment we’re not giving version numbers to rhg separate from the Mercurial version. Differential Revision: https://phab.mercurial-scm.org/D10144

rhg: Exit with an error code if `files` finds nothing This matches the behavior of Python-based hg. Differential Revision: https://phab.mercurial-scm.org/D10143

rhg: `cat` command: print error messages for missing files And exit with an error code if no file was matched. This matches the behavior of Python-based hg. Differential Revision: https://phab.mercurial-scm.org/D10142

rhg: Silently ignore missing files in config %include … instead of aborting with an error message. This is what Python-based hg does. Differential Revision: https://phab.mercurial-scm.org/D10141

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