wireprotov2: remove "compression" from capabilities response This is not used. And future commits will change how this mechanism works. Let's remove it. As a bonus, this fixes some test failures on pure installs (due to zstd references). Differential Revision: https://phab.mercurial-scm.org/D4912

zstandard: vendor python-zstandard 0.10.1 This was just released. The upstream source distribution from PyPI was extracted. Unwanted files were removed. The clang-format ignore list was updated to reflect the new source of files. setup.py was updated to pass a new argument to python-zstandard's function for returning an Extension instance. Upstream had to change to use relative paths because Python 3.7's packaging doesn't seem to like absolute paths when defining sources, includes, etc. The default relative path calculation is relative to setup_zstd.py which is different from the directory of Mercurial's setup.py. The project contains a vendored copy of zstandard 1.3.6. The old version was 1.3.4. The API should be backwards compatible and nothing in core should need adjusted. However, there is a new "chunker" API that we may find useful in places where we want to emit compressed chunks of a fixed size. There are a pair of bug fixes in 0.10.0 with regards to compressobj() and decompressobj() when block flushing is used. I actually found these bugs when introducing these APIs in Mercurial! But existing Mercurial code is not affected because we don't perform block flushing. # no-check-commit because 3rd party code has different style guidelines Differential Revision: https://phab.mercurial-scm.org/D4911

rust-chg: install signal handlers to forward signals to server I use sync::Once as a synchronization primitive because it's quite easy to use, and is good enough to prevent data race in these C functions.

rust-chg: remove SIGCHLD handler which won't work in oxidized chg Since pager is managed by the Rust part, the C code doesn't know the pager pid. I could make the Rust part teach the pid to C, but still installing SIGCHLD handler seems horrible idea since we no longer use handcrafted low-level process management functions. Instead, I'm thinking of adding async handler to send SIGPIPE at the exit of the pager.

rust-chg: extract signal handlers from chg/procutil.c abortmsgerrno() and debugmsg() are removed, and the public interface instead returns success/error status. Since signal handlers can't propagate errors, the result of kill() is just ignored.

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chgserver: catch Abort while parsing early args to shut down cleanly _loadnewui() calls dispatcher functions, which may raise Abort if unparsable arguments are passed in. The server should catch such errors and translate them to the "exit 255" instruction so the client can finish the IPC session cleanly. Spotted while porting the chg client to Rust.

chg: upgrade client to use "setumask2" command No compatibility code is added to the client side, since it's unlikely for new client to communicate with the old server.

chgserver: add "setumask2" command which uses correct message frame The first 4 bytes should be a length field, not a value. Spotted while porting chg functions to the Rust one.