pager: skip running the pager if it's set to 'cat' Avoid useless uses of cat.

pager: avoid shell=True on subprocess.Popen for better errors (issue5491) man(1) behaves as poorly as Mercurial without this change. This cribs from git's run-command[0], which has a list of characters that imply a string that needs to be run using 'sh -c'. If none of those characters are present in the command string, we can use shell=False mode on subprocess and get significantly better error messages (see the test) when the pager process is invalid. With a complicated pager command (that contains one of the unsafe characters), we behave as we do today (which is no worse than git manages.) I briefly tried tapdancing in a thread to catch early pager exits, but it's just too perilous: you get races between fd duping operations and a bad pager exiting, and it's too hard to differentiate between a slow-bad-pager result and a fast-human-quit-pager-early result. I've observed some weird variation in exit code handling in the "bad experience" case in test-pager.t: on my Mac hg predictably exits nonzero, but on Linux hg always exits zero in that case. For now, we'll work around it with || true. :( 0: https://github.com/git/git/blob/cddbda4bc87b9d2c985b6749b1cf026b15e2d3e7/run-command.c#L201

py3: change explicit conversion of config value from str to pycompat.bytestr

py3: add __bool__ to every class defining __nonzero__ __nonzero__ was renamed to __bool__ in Python 3. This patch simply aliases __bool__ to __nonzero__ for every class implementing __nonzero__.

merge: also allow 'e' action with experimental.updatecheck=noconflict With experimental.updatecheck=noconflict set, if one checks out f3398f1f70a0 (tests: add execute bit and fix shbang line, 2015-12-22) and then try to check out its parent, hg will complain about conflicting changes, even though the working directory is clean. We need to also allow the 'e' action in merge.py. The 'e' action is used when moving to a commit where the only change to the file is to its executable flag, so it's just an optimized 'g' action. Doesn't seem to be worth writing a test for, since the existing setup in test-update-branches.t does not set any flags.

exchange: use v2 bundles for modern compression engines (issue5506) Previously, `hg bundle zstd` on a non-generaldelta repo would attempt to use a v1 bundle. This would fail because zstd is not supported on v1 bundles. This patch changes the behavior to automatically use a v2 bundle when the user explicitly requests a bundlespec that is a compression engine not supported on v1. If the bundlespec is <engine>-v1, it is still explicitly rejected because that request cannot be fulfilled.

exchange: reject new compression engines for v1 bundles (issue5506) Version 1 bundles only support a fixed set of compression engines. Before this change, we would accept any compression engine for v1 bundles, even those that may not work on v1. This could lead to an error. We define a fixed set of compression engines known to work with v1 bundles and we add checking to ensure a newer engine (like zstd) won't work with v1 bundles. I also took the liberty of adding test coverage for unknown compression names because I noticed we didn't have coverage of it before.

config: honour the trusted flag in ui.configbytes

osutil: fix potential wrong fd close According to POSIX closedir [1]: If a file descriptor is used to implement type DIR, that file descriptor shall be closed. According to POSIX fdopendir [2]: Upon calling closedir() the file descriptor shall be closed. So we should avoid "close(dfd)" after "closedir(dir)". With threads, there could be a race where an innocent fd gets closed. But Python GIL seems to help hiding the issue well. [1]: http://pubs.opengroup.org/onlinepubs/009695399/functions/closedir.html [2]: http://pubs.opengroup.org/onlinepubs/9699919799/functions/fdopendir.html

parsers: use Python memory allocator for indexObject->offsets