util: implement pop() on lrucachedict This moves __delitem__() to pop() as the requirement is pretty much the same, and reimplement __delitem__() by using pop().

util: add method to peek item in lrucachedict I want a function that doesn't unnecessarily update the internal state of the cache dict after fork().

commandserver: loop over selector events An IPC socket will be waited by the same selector.

commandserver: remove redundant "if True" block

commandserver: extract handler of new socket connection This prepares for adding an IPC socket.

commandserver: pass around option to hook repo instance creation This is necessary to wrap a repo instance so the master process will be notified on repo.close().

py3: stop subscripting socket.error In 3.3 and later, this is now an alias for OSError. I hacked up the server code enough that I was able to trigger the exception handler in server.py from test-http-bundle1.t. Other instances of this either subscript through the `args` member, or reference the errno or strerror attributes. Note that on Windows, the errno value seems to reflect the Winsock error, so the various tests for EPIPE seem like they would always fail. But that seems to be the case in py2 as well.

test: update test-logtoprocess.t to not requires less The test previously assumed that a working pager was present in the test environment. Update it to use the fakepager instead. Differential Revision: https://phab.mercurial-scm.org/D5399