Enable pre-push unit test check via pre-commit

Adds a new pre-push hook to .pre-commit-config.yaml that runs
`pytest unit_tests/` before allowing any push, including `git review`.

This ensures that regressions in fast-running unit tests are caught
before changes are submitted for review.

To activate the hook locally:
  pre-commit install --hook-type pre-commit
  pre-commit install --hook-type pre-push

Change-Id: Ia2d0fe56eabf6466e27f0432ac2fb91c7b444832
Signed-off-by: Andrew Vaillancourt <andrew.vaillancourt@windriver.com>

.pre-commit-config.yaml

@@ -72,3 +72,10 @@ repos:
       language: python
       types: [python]
       args: ["--fail-under", "100", "--ignore-module", "--ignore-init-method", "--ignore-nested-functions", "--verbose"]
+
+    - id: unit-tests
+      name: Run unit tests before push
+      entry: bash -c 'pytest unit_tests/'
+      language: system
+      pass_filenames: false
+      stages: [push]

README.rst

@@ -99,10 +99,13 @@ Setup and Installation
 
 4. **Install Pre-Commit Hooks**:
 
+   Pre-commit hooks are used to enforce code formatting, linting, and unit testing before code is committed or pushed for review.
+
    .. code-block:: bash
 
-      # Install pre-commit hooks for linting and formatting (run in the repository's root directory)
-      pre-commit install
+      # Install hooks for commit-time (linting, formatting) and push-time (unit test enforcement)
+      pre-commit install --hook-type pre-commit
+      pre-commit install --hook-type pre-push
 
 Configuration
 -------------