cmdserver: add service that listens on unix domain socket and forks process Typical use case of 'unix' mode is a background hg daemon. $ hg serve --cmdserver unix --cwd / -a /tmp/hg-`id -u`.sock Unlike 'pipe' mode in which parent process keeps stdio channel, 'unix' server can be detached. So clients can freely connect and disconnect from server, saving Python start-up time. It might be better to write "--cmdserver socket -a unix:/sockpath" instead of "--cmdserver unix -a /sockpath" in case hgweb gets the ability to listen on unix domain socket.

test-commandserver: add connector for unix domain socket server The next patch will introduce --cmdserver unix.

test-commandserver: allow check() to make connection in different way The next patch will add connector for 'unix' mode server.

test-commandserver: remove unused repopath argument from check() Instead of repopath, check() will receive connect() function as argument. It will allow to connect to server of different mode.

cmdserver: make server streams switchable In 'unix' mode, server instance will be created per connection, and fin/fout are set to socket files.

cmdserver: switch service objects by mode server class will be changed to accept fin/fout pair instead of mode string so that it can interact with socket files.