When using many plugins, vim-plug may spawn many git processes for them.
* get revision
* get branch
* get remote.origin.url
This is too heavy. especially on Windows. This change get revision, branch,
remote origin url directly from .git directory.
This idea is borrowed from @k-takata's commit for minpac.
Executing external programs is slow especially on Windows.
Read the information directly from .git directory.
Specify PIPE as stdin for subprocess.Pipe for gvim.exe.
Also fixes some ruby implementation.
* windows doesn't have pgrep.
* windows can't handle SIGTERM.
* windows can't handle /dev/null
* redraw always
Yasuhiro Matsumoto
