use --depth 1 for git clone + use separate git fetch to download rev

[ubunatic]

Summary of changes

• use --depth 1 with git clone to get a shallow clone of a required repo
• use a separate git fetch --depth 1 to fetch a specific revision from the shallow clone

Closes #1446

Pull Request Checklist

• Changes have tests
• News fragment added in changelog.d. See documentation for details

Manual Tests

I did not find any git-download tests to extend and currently only tested manually using:

• python3.6 -m easy_install --user -v git+ssh://[email protected]/private/repo.git@master
• python3.6 -m easy_install --user -v git+ssh://[email protected]/private/repo.git

[ubunatic]

closing, since this is already discussed in pip

[mrx23dot]

What was the conclusion? It's still not implemented in 2022.

[ubunatic]

There was some discussion about ways to configure it in the URL, but I do not know the status of that (see: pypa/pip#2432 (comment)).
At least having it as default is off the table to safe backwards compatibility.

[mrx23dot]

Thanks, we can always manually git clone a shallow one and install it locally in case repo is huge.