chgserver: reorder service classes to make future patches readable Includes no functional change.

commandserver: add new forking server implemented without using SocketServer SocketServer.ForkingMixIn of Python 2.x has a couple of issues, such as: - race condition that leads to 100% CPU usage (Python 2.6) https://bugs.python.org/issue21491 - can't wait for children belonging to different process groups (Python 2.6) - leaves at least one zombie process (Python 2.6, 2.7) https://bugs.python.org/issue11109 The first two are critical because we do setpgid(0, 0) in child process to isolate terminal signals. The last one isn't, but ForkingMixIn seems to be doing silly. So there are two choices: a) backport and maintain SocketServer until we can drop support for Python 2.x b) replace SocketServer by simpler one and eliminate glue codes I chose (b) because it's great time for getting rid of utterly complicated SocketServer stuff, and preparing for future move towards prefork service. New unixforkingservice is implemented loosely based on chg 531f8ef64be6. It is monolithic but much simpler than SocketServer. unixservicehandler provides customizing points for chg, and it will be shared with future prefork service. Old unixservice class is still used by chgserver. It will be removed later. Thanks to Jun Wu for investigating these issues.

commandserver: extract function that serves for the current connection This will be used by new server implementation.

commandserver: manually create file objects from socket Prepares for moving away from SocketServer. See the subsequent patches for why.

bdiff: split bdiff into cpy-aware and cpy-agnostic part

bdiff: rename functions and structs to be amenable for later exporting

bdiff: use ssize_t in favor of Py_ssize_t in cpython-unaware locations This function and struct will be exposed via cffi, so we need to remove the cpython API dependency they currently have.

hgweb: enumerate lines in loop header, not before Doing this will allow access to the lines in arbitrary order (because the result of enumerate() is an iterator), and that will help calculating rowspan for annotate blocks.

sslutil: add assertion to prevent accidental CA usage on Windows Yuya suggested we add this check to ensure we don't accidentally try to load user-writable paths on Windows if we change the control flow of this function later.

shelve: make unshelve be able to abort in any case