use lightweight checkout

[kzadorozhny]

Optimize git commands used by the create_gitops_prs tool to support referencing shallow repository clones via --mirror parameter.

Replace gitops repository clone command:

git clone --no-checkout --reference <mirrorDir>  <repo> <gitopsWorkDir>

with the sequence of commands:

git clone --no-checkout  --single-branch --branch <primaryBranch> --filter=blob:none  --no-tags --reference <mirrorDir>  <repo> <gitopsWorkDir>
git remote set-branches --add origin "deploy/*"
git fetch --force --filter=blob:none --no-tags origin