py3: ensure the proxied Windows fd doesn't escape by entering context manager The purpose of the proxy class is to provide the `name` attribute which contains the file path. But in tests that used a context manager, it still blew up complaining that 'int' doesn't have a 'startswith' function.

merge with stable

templatefuncs: specialize "no match" value of search() to allow % operation If Python had Maybe or Option, the type of the search() result would be Option<Mapping>, which can be considered as a 0/1 container of a Mapping. So it makes sense that {search(r'no match pattern', x) % "whatever"} is mapped to an empty string.

templatefuncs: add regexp search() function that extracts substring This can be used to extract an issue number from a commit message, for example: {search(r'\(issue([0-9]*)\)', desc) % '{1}'}

rust: changed Graph.parents to return [Revision; 2] This will allow for simple iteration on parent revisions, such as: for parent in graph.parents(rev)?.iter().cloned() This seems to be a zero overhead abstraction once built in release mode. Differential Revision: https://phab.mercurial-scm.org/D5415

rust: improved docstring In the previous wording, rustfmt wanted to cut at the == which is not very readable in my taste. Differential Revision: https://phab.mercurial-scm.org/D5414

revset: move subscript relation functions to its own dict This will help adding more relation functions in extensions. We skip short names (that consist of one letter) while raising UnknownIdentifier because such names cannot be suggested anyway: the similarity cutoff in dispatch._getsimilar() is currently 0.6.

py3: teach run-tests.py to handle exe with spaces when --local isn't specified This was the reason that no amount of quoting worked in test-hghave.t. `os.popen()` needed to be swapped out because while the added quoting around line 3124 worked on py3, it failed on py2. See 38d51371792b. The problem with `os.system()` was wrongly splitting the command on the space in 'Program Files', regardless of quoting. It looks like there are a few other instances of `os.system()` in core code, so presumably those should be replaced?

rust: adapted hg-core tests for iteration over Result Now AncestorsIterator iters on Result<Revision, GraphError>

win32: close the handles associated with a spawned child process Probably not a big deal because at this point, the call is only used when spawning a daemonized server. In that case, the parent process goes away first, so it won't prevent the child from being cleaned up.

rust: remove comment about error handling of AncestorsIterator To be align with 443eb4bc41af "rust: propagate error of index_get_parents() properly." Spotted by Georges Racinet.

test: fix test-http-bad-server with current python 2.7 https://github.com/python/cpython/pull/2825 changed the exception message for empty http status line. Differential Revision: https://phab.mercurial-scm.org/D5412