commandserver: use selectors2 Previously, commandserver was using select.select. That could have issue if _sock.fileno() >= FD_SETSIZE (usually 1024), which raises: ValueError: filedescriptor out of range in select() We got that in production today, although it's the code opening that many files to blame, it seems better for commandserver to work in this case. There are multiple way to "solve" it, like preserving a fd with a small number and swap it with sock using dup2(). But upgrading to a modern selector supported by the system seems to be the most correct way.

selector2: vendor selector2 library This library was a backport of the Python 3 "selectors" library. It is useful to provide a better selector interface for Python2, to address some issues of the plain old select.select, mentioned in the next patch. The code [1] was ported using the MIT license, with some minor modifications to make our test happy: 1. "# no-check-code" was added since it's foreign code. 2. "from __future__ import absolute_import" was added. 3. "from collections import namedtuple, Mapping" changed to avoid direct symbol import. [1]: https://github.com/SethMichaelLarson/selectors2/blob/d27dbd2fdc48331fb76ed431f44b6e6956de7f82/selectors2.py # no-check-commit

context: name files relative to cwd in warning messages I was several directories deep in the kernel tree, ran `hg add`, and got the warning about the size of one of the files. I noticed that it suggested undoing the add with a specific revert command. The problem is, it would have failed since the path printed was relative to the repo root instead of cwd. While here, I just fixed the other messages too. As an added benefit, these messages now look the same as the verbose/inexact messages for the corresponding command. I don't think most of these messages are reachable (typically the corresponding cmdutil function does the check). I wasn't able to figure out why the keyword tests were failing when using pathto()- I couldn't cause an absolute path to be used by manipulating the --cwd flag on a regular add. (I did notice that keyword is adding the file without holding wlock.)