vcsrepo git provider support for different ssh port

Current version of vcsrepo does not support the scenario where the ssh port of a repository is different than the default one when using an ssh key.

For example for repositories with a URL like

ssh://git@example.com:7999/example/example.git

the git resource should be something like

vcsrepo { "path_to_resource":

  ensure   => present,

  provider => git,

  source   => "git@example.com:example/example.git",

  identity => '/root/.ssh/deploykey_rsa',

  port     => '7999'

}

that will map to something like in the GIT_SSH file

exec ssh ... -i /root/.ssh/deploykey_rsa -p 7999 $*