tests: replace [[]] bashism with portable [] invocation In this case nothing fancy is required. Differential Revision: https://phab.mercurial-scm.org/D7596

rust-hg-path: implement `Display` for `HgPath` and `HgPathBuf` This is useful when debugging, to get a human readable output instead of an array of `u8`. Differential Revision: https://phab.mercurial-scm.org/D7523

rust-performance: introduce FastHashMap type alias for HashMap Rust's default hashing is slow, because it is meant for preventing collision attacks. For all of the current Rust code, we don't care about those attacks, because if an person with bad intentions has write access to your repo, you have other issues. I've chosen to use the TwoXHash crate because it was made by a reputable member of the Rust community and has very good benchmarks. For now it does not seem to improve performance by much for the current code, but it's something else to not worry about when benchmarking code: in a previous experiment with copytracing in Rust, it accounted for more than 10% of the time of the entire script. Differential Revision: https://phab.mercurial-scm.org/D7116

mail: use procutil.shellsplit instead of bytes.split to parse command Differential Revision: https://phab.mercurial-scm.org/D7541

annotate: describe --skip as taking a revset It's obvious to me, but probably wouldn't be obvious to a novice user. Differential Revision: https://phab.mercurial-scm.org/D7557

automation: use latest Windows AMI as base It looks like the previous base image no longer exists. I guess Amazon expires them or something. Let's switch to the newest version of the equivalent image. Differential Revision: https://phab.mercurial-scm.org/D7571