dispatch: change cwd when loading local config
Previously, the `_getlocal` function would not correctly load the repo config
when given a relative `rpath` and an alternate cwd via the `wd` parameter.
Normally when `--cwd` is specified, hg changes to the given directory before
attempting to load the local config (and therefore does not specify a `wd`).
The only time the function is called with `wd` set is when hg is running as a
command server (e.g., with chg), in which case each forked worker process will
attempt to configure itself via `_getlocal` before responding to the client.
When given a relative repo path, the worker fails to load the repo config,
detects a config mismatch with the client, and enters a redirect/respawn loop.
To fix this, we can simply change to the desired working directory during
config loading. (Note that simply concatenating `wd` and `rpath` won't work
in all cases. The repo path could be something more complicated than a simple
relative path, such as a `union:` repo.)
Octopus Merge Support
=====================
This will be moderately complicated, as we'll need to synthesize phony
changeset entries to explode the octopus into "revisions" that only
have two parents each. For today, we can probably just do something like
aaaaaaaaaaaaaaaaaaXX{20 bytes of exploded node's hex sha}
where XX is a counter (so we could have as many as 255 parents in a
git commit - more than I think we'd ever see.) That means that we can
install some check in this extension to disallow checking out or
otherwise interacting with the `aaaaaaaaaaaaaaaaaa` revisions.
Interface Creation
====================
We at least need an interface definition for `changelog` in core that
this extension can satisfy, and again for `basicstore`.
Reason About Locking
====================
We should spend some time thinking hard about locking, especially on
.git/index etc. We're probably adequately locking the _git_
repository, but may not have enough locking correctness in places
where hg does locking that git isn't aware of (notably the working
copy, which I believe Git does not lock.)