The benefit of doing this is that we can now handle directories that
contain symlinks and other arbitrary things, such as the static_test_env
required by filesystem tests.
As a fly-by fix, we also accumulate several commands to perform over SSH
and execute them at once instead of SSHing several times. This should be
faster on average.
If a ShTest has for example another command in front of the test
executable it wants to execute, ssh.py needs to properly translate
the path of that test executable to the executable on the remote host.
For example, running '%{exec} ! %t.exe', we can't assume that the
test-executable is the first argument after '%{exec}'.
Louis Dionne