feature: allow suffixing repository urls with .git #255

git clone https://tangled.org/@tangled.org/core works as expected, but git clone https://tangled.org/@tangled.org/core.git fails with

Cloning into 'core'...
fatal: https://tangled.org/@tangled.org/core.git/info/refs not valid: is this a git repository?

Suffixing repositories with .git is a common pattern for package managers, especially for AUR (Arch User Repository) package sources.