github: enable github actions for postsubmit testing

This gives us a bit of feedback by running our testsuite on Linux,
macOS, and Windows platforms.   While Linux & macOS are passing,
Windows fails some of them.  We can figure that out later.  This
is better than what we have now which is manual one-offs.

Change-Id: I9d2d644be97ec76645db0bc15739e7679310a647
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/255314
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>

.github/workflows/test-ci.yml

@@ -0,0 +1,31 @@
+# GitHub actions workflow.
+# https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions
+
+name: Test CI
+
+on:
+  push:
+    branches: [master, repo-1, stable, maint]
+    tags: [v*]
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: [2.7, 3.6, 3.7, 3.8]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install tox tox-gh-actions
+    - name: Test with tox
+      run: tox

README.md

@@ -15,6 +15,8 @@ that you can put anywhere in your path.
 * [repo Hooks](./docs/repo-hooks.md)
 * [Submitting patches](./SUBMITTING_PATCHES.md)
 * Running Repo in [Microsoft Windows](./docs/windows.md)
+* GitHub mirror: <https://github.com/GerritCodeReview/git-repo>
+* Postsubmit tests: <https://github.com/GerritCodeReview/git-repo/actions>
 
 ## Install
 

tox.ini

@@ -17,6 +17,13 @@
 [tox]
 envlist = py27, py36, py37, py38
 
+[gh-actions]
+python =
+    2.7: py27
+    3.6: py36
+    3.7: py37
+    3.8: py38
+
 [testenv]
 deps = pytest
 commands = {envpython} run_tests