Fixes pushing constraints (#15243)

Afer merging the constraints, the 'recursive' mode was not added
to checkout resulting with non-checked out github push action.

This commit fixes it and adds color to diff output in commit
to better show differences when pushing.

.github/workflows/ci.yml

@@ -1157,6 +1157,7 @@ ${{ hashFiles('.pre-commit-config.yaml') }}"
         uses: actions/checkout@v2
         with:
           persist-credentials: false
+          submodules: recursive
       - name: "Setup python"
         uses: actions/setup-python@v2
         with:

scripts/ci/constraints/ci_commit_constraints.sh

@@ -22,7 +22,7 @@ cp -v ./files/constraints-*/constraints*.txt repo/
 cd repo || exit 1
 git config --local user.email "dev@airflow.apache.org"
 git config --local user.name "Automated GitHub Actions commit"
-git diff --exit-code || git commit --all --message "Updating constraints. Build id:${CI_BUILD_ID}
+git diff --color --exit-code || git commit --all --message "Updating constraints. Build id:${CI_BUILD_ID}
 
 This update in constraints is automatically committed by the CI 'constraints-push' step based on
 HEAD of '${CI_REF}' in '${CI_TARGET_REPO}'