Add support for partial git clones (git clone --filter)

Problem Definition

If Bamboo is only requires certain subdirectory of a repository to perform a build, Git only allows a clone of the entire repository. When a repository is large (Example: 1GB+) it can take some time to clone files that may not be required.

Suggested Solution

Since Git 2.18, Git protocol v2 has introduced the --filter flag to enable partial clones

This will allow Bamboo to clone specific subdirectories of a repository only.

Why this is important

This will increase cloning performance on large repositories.