feat: only clone init templates when required

[mildaniel]

Which issue(s) does this change fix?

N/A

Why is this change necessary?

AWS SAM CLI stores the cloned app templates in a local directory, but doesn't use it as a cache. The app templates repository doesn't need to be cloned every time if it is already up-to-date.

How does it address the issue?

Checks if the app templates repository needs to be cloned before cloning based on latest commit hash.

What side effects does this change have?

The .git directory in the app templates folder will now be copied to the cache directory whereas before it was excluded.

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• Add input/output type hints to new functions/methods
• Write design document if needed (Do I need to write a design document?)
• Write/update unit tests
• Write/update integration tests
• Write/update functional tests if needed
• make pr passes
• make update-reproducible-reqs if dependencies were changed
• Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[sriram-mv]

I like where this is going and have been thinking of doing this same improvement for a while.

It should improve perf on sam init especially on not so great internet connections.