Fix Git tree caching (for repo:ls command)
Fix Git tree caching (for repo:ls command)

The cache key was wrong, meaning Git trees were cached indefinitely for each
environment. They will now be cached according to the commit hash.

platformsh/platformsh-cli,pjcdawkins/platformsh-cli,pjcdawkins/platformsh-cli,platformsh/platformsh-cli,pjcdawkins/platformsh-cli,platformsh/platformsh-cli