It looks like v1.7.2 caused a regression. #300 caused a regression that unsets an existing GIT_SSH_COMMAND env variable if it is set.

Problem

If I have GIT_SSH_COMMAND="ssh -o 'StrictHostKeyChecking=no'" and no sshKey query param set, go-getter is not passing the StrictHostKeyChecking=no option when downloading the repo.

Expected

From what I understand from #299 we want to leave the GIT_SSH_COMMAND untouched when an sshKey param is not set.

Although #300 fixed the case so GIT_SSH_COMMAND isn't set to GIT_SSH_COMMAND=ssh when a sshKey param is not used, it also unset it if it had an existing value. I think if GIT_SSH_COMMAND is already set in the environment then it should be left unchanged.