worker: use one pipe per posix worker and select() in parent process...
worker: use one pipe per posix worker and select() in parent process
This allows us to pass results larger than PIPE_BUF through the pipes without
interleaving them. This is necessary now because "hg fix" sends file contents
as the result from workers.
Differential Revision:
https://phab.mercurial-scm.org/D3960