makefile: add a install option This gives and easy way to install rhg that we can use in `run-test.py` in the next changesets. Differential Revision: https://phab.mercurial-scm.org/D10194

makefile: add a build-rhg option This gives an easy action to build the rhg-binary. This will be useful for the `install-rhg` action in the next changeset. Differential Revision: https://phab.mercurial-scm.org/D10193

makefile: add a install-chg option This is done as a gratuitous improvement on the way to add makefile entry to build and install rhg. It seems saner to have equivalent entry for chg too. Differential Revision: https://phab.mercurial-scm.org/D10192

makefile: add a build-chg option This is done as a gratuitous improvement on the way to add makefile entry to build and install rhg. It seems saner to have equivalent entry for chg too. Differential Revision: https://phab.mercurial-scm.org/D10191

tests: Disable for rhg remaining tests that fail in that mode These cases are in features not yet implemented by rhg for which triggering a fallback is not practical. Disabling some tests allows us to reach passing CI and catch any future regression in the rest of the tests. Differential Revision: https://phab.mercurial-scm.org/D10190

rhg: Remove `rhg.fallback-executable=hg` default configuration When `rhg.on-unsupported` is configured to `fallback` and an unsupported feature is encountered, the previous default was to look for an `hg` executable in `$PATH`. This default was fragile since it was easy to end up accidentally using an older version of Mercurial installed system-wide, when a local (perhaps patched) installation was intended. Instead, it is now an error to have `rhg.on-unsupported=fallback` without also configuring an explicit path or the fallback executable. Differential Revision: https://phab.mercurial-scm.org/D10189

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

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

rhg: Add an allow-list of ignored extensions Because rhg doesn’t know how a Python extension would affect behavior it implements in Rust, when an unsupported extension is enabled it conservatively falls back to Python-based hg. However many users will have unsupported extensions enabled in practice. Maybe they don’t actually affect rhg behavior, but we don’t know. This adds a `rhg.ignored-extensions` configuration that lets users list extensions that rhg can safely ignore and proceed even if they’re not supported in Rust. Differential Revision: https://phab.mercurial-scm.org/D10188

rhg: Fall back to Python if unsupported extensions are enabled Extensions might affect behavior in ways we can’t anticipate, so just ignoring them is not correct. Later we’ll add opt-in configuration to ignore specific extensions. Differential Revision: https://phab.mercurial-scm.org/D10112

rhg: Sort config files when adding a directory For example in `/etc/mercurial/hgrc.d/` or with `HGRCPATH=some-directory`. Previously files where parsed in the order returned by the filesystem, which is undefined. But order is significant when multiple files define the same configuration key: the "last" one wins. Differential Revision: https://phab.mercurial-scm.org/D10111

rhg: Align config file parse error formatting with Python Differences can cause tests to fail Differential Revision: https://phab.mercurial-scm.org/D10110

rhg: Fall back to Python for bundle repositories rhg does not support bundles at all, yet. Differential Revision: https://phab.mercurial-scm.org/D10102

rhg: Fall back to Python on --repository with an URL A low-hanging fruit to improve on this would be to properly parse and handle `file:` URLs. But other Python-based hg supports some other URL schemes for features that rhg does not support yet. Differential Revision: https://phab.mercurial-scm.org/D10101

rhg: Print non-absolutized path in "repository {} not found" errors … like Python does. Differences in ouput can cause tests to fail. Differential Revision: https://phab.mercurial-scm.org/D10100

rhg: Align "malformed --config" error message with Python Differences in error message formatting can cause tests to fail. Differential Revision: https://phab.mercurial-scm.org/D10099

rhg: Fall back to Python on unsupported `rhg config <section>` Printing an entire section (as opposed to a single value with `rhg config foo.bar`) is not supported yet in Rust only. Differential Revision: https://phab.mercurial-scm.org/D10098

rhg: Fall back to Python for unsupported revset syntax rhg only supports a small subset of the syntax. On parse error, this gives Python a chance instead of aborting immediately. Differential Revision: https://phab.mercurial-scm.org/D10097

tests: Add `rhg` and `no-rhg` for #require and #if in .t files With this we can allow some small differences in expected output between Rust-based and Python-based code paths. Differential Revision: https://phab.mercurial-scm.org/D10096

tests: Enable rhg fallback to Python by default in tests This premise of `run-tests.py --rhg`: fallback should make `rhg` behave the same as `hg`, except faster in some cases. To test run the whole test suite with installed `rhg` as `hg` and with fallback enabled. Differential Revision: https://phab.mercurial-scm.org/D10187

rhg: Add environment variables for fallback configuration For the `rust-tests.py --rhg` we want every `hg` command in tests to run `rhg` with fallback enabled, but other methods of setting configuration are limited or disruptive as discussed in code comment. Differential Revision: https://phab.mercurial-scm.org/D10186