sslutil: fix names of variables containing minimum protocol strings When working in this module, I found it very confusing that "protocol" as a variable name could mean either "minimum protocol string" or an exact version (as a string or ssl.PROTOCOL_* value). This patch prefixes variables of the former type with "minimum".

sslutil: stop returning argument as third return value of protocolsettings() The third return value was always the same as the argument.

relnotes: note that we now require modern SSL/TLS features in Python

tests: stop checking for optional, now impossible output In 7dd63a8cb1ee, the code that could output that line was removed.

rust: remove one more occurrence of re2 Differential Revision: https://phab.mercurial-scm.org/D8601

scmutil: clarify getuipathfn comment Differential Revision: https://phab.mercurial-scm.org/D8600

githelp: add some minimal help for pickaxe functionality Due to a conversation in work chat, I realized this is actually pretty well-hidden in Mercurial. Differential Revision: https://phab.mercurial-scm.org/D8590

rust: remove duplicate import Differential Revision: https://phab.mercurial-scm.org/D8456

tests: remove "sslcontext" check Now that we require the presence of ssl.SSLContext in setup.py, the check would always return `True`.

sslutil: eliminate `_canloaddefaultcerts` by constant-folding code using it

tests: remove "defaultcacerts" check `sslutil._canloaddefaultcerts` is always true (and will be removed).

sslutil: eliminate `modernssl` by constant-folding code using it

hgweb: avoid using `sslutil.modernssl` `sslutil.modernssl` is going to be removed. Since the point of using this attribute was to check the importability of the `sslutil`, a different attribute can be used. `sslutil.wrapserversocket` is used because it’s anyway used a few lines below.

sslutil: remove comments referring to removed SSLContext emulation class

sslutil: remove code checking for presence of ssl.SSLContext Now that we require the presence of ssl.SSLContext in setup.py, we can remove this code.

setup: require a Python version with modern SSL features This increases the minimum security baseline of Mercurial and enables us to remove compatibility code for supporting older, less secure Python versions.

sslutil: set `_canloaddefaultcerts` to `True` if `ssl.SSLContext` is present The `load_default_certs()` method was already present when `ssl.SSLContext` was backported to Python 2.7 (https://hg.python.org/cpython/rev/221a1f9155e2).

filemerge: add __bytes__ for absentfilectx This will at _least_ aid some upcoming debugging. Differential Revision: https://phab.mercurial-scm.org/D8592

mergestate: move staticmethod _filectxorabsent to module level I suspect this was a static method just because it made merge.py feel less messy, but now we have a mergestate package so we can do better. Differential Revision: https://phab.mercurial-scm.org/D8591

rust: remove support for `re2` With the performance issues with `regex` figured out and fixed in previous patches and `regex` newly gaining support for empty alternations, there is no reason to keep `re2` around anymore. It's only *marginally* faster at creating the regex which saves at most a couple of ms, but gets beaten by `regex` in every other aspect. This removes the Rust/C/C++ bridge (hooray!), the `with-re2` feature, the conditional code that goes with it, the documentation and relevant part of the debug/module output. Differential Revision: https://phab.mercurial-scm.org/D8594

rust-dependencies: update `regex` to 1.3.9 Version `1.3.8` introduces support for empty alternations, which makes previously disallowed patterns usable in `regex`. From a user's perspective, this means that glob patterns like `*.py{,c}` will no longer generate an "invalid" regex and will use the Rust path. `1.3.9` is a bugfix release, might as well update to the latest one. Differential Revision: https://phab.mercurial-scm.org/D8593

cleanup: remove compatibility code for Python < 2.7.4 The minimum supported Python version was recently raised to 2.7.4.

cleanup: eliminate procutil.quotecommand() After some compatibility code was removed, the function was the identity function on all platforms.

cleanup: remove compatibility code for Python < 2.7.1 The minimum supported Python version was recently raised to 2.7.4.

grep: reduce the cost of pathauditor checks when grepping working copy Running `time hg grep zxczxczxczxczxc -l` on mozilla-central: before: real 0m20,000s user 0m15,796s sys 0m4,189s after: real 0m10,903s user 0m8,964s sys 0m1,916s if vfs didn't call pathauditor at all: real 0m7,781s user 0m5,968s sys 0m1,790s Differential Revision: https://phab.mercurial-scm.org/D8582

grep: test that paths get audited Differential Revision: https://phab.mercurial-scm.org/D8581

grep: add test coverage of behavior on symlinks Differential Revision: https://phab.mercurial-scm.org/D8580

help: fix description of revlog version 2 Differential Revision: https://phab.mercurial-scm.org/D8576