extensions: load help from hgext.__index__ as a fallback this time
Prior to 843418dc0b1b, `hgext.__index__` was consulted first if present, which
caused the longer help from the extension modules to be ignored, even when
available. But that change causes a bunch of test failures when the pyoxidized
binary bundles *.pyc in the binary, saying the there's no help topic for
`hg help $disabled_extension` and suggesting the use of `--keyword`, rather than
showing a summary and indicating that it is disabled. Current failures were in
test-check-help.t, test-extension.t, test-help.t, and test-qrecord.t.
Ideally, we would read the various *.pyc files from memory and slurp in the
docstring, but I know that they used to not be readable as resources, and I
can't figure out how to make it work now. So maybe 3.9 and/or the current
PyOxidizer doesn't support it yet. I got closer in py2exe with
`importlib.resources.open_binary("hgext", "rebase.pyc")`, but `open_binary()` on
*.pyc fails in pyoxidizer.[1] Either way, the *.pyc can't be passed to
`ast.parse()` as `extensions._disabledcmdtable()` is doing, so I'm setting that
aside for now.
[1] https://github.com/indygreg/PyOxidizer/issues/649
https://bz.mercurial-scm.org/619
$ hg init repo
$ cd repo
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
adding b
$ hg co -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Fast-forward:
$ hg merge b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -Ammerge
Bogus fast-forward should fail:
$ hg merge b
abort: merging with a working directory ancestor has no effect
[255]
Even with strange revset (issue4465)
$ hg merge ::.
abort: merging with a working directory ancestor has no effect
[255]