Switch to using Github Actions CI (bp #1690) (#1700)

* Switch to using Github Actions CI (#1690)

MiMa binary compatibility checks are now run on master, but the
mimaPreviousArtifacts are empty which makes the check a no-op. This
helps keep both the build.sbt and CI more consistent between master and
stable branches.

.mergify.yml is also updated with mergify.sc from chisel-repo-tools
using the following configuration:

conditions:
  - status-success=all tests passed
branches:
  - 3.2.x
  - 3.3.x
  - 3.4.x
(cherry picked from commit 25a417f)

# Conflicts:
#	.mergify.yml
#	build.sbt
#	project/plugins.sbt

* Resolve merge conflicts and remove docs tests

Docs tests were added in 3.4

Co-authored-by: Jack Koenig <[email protected]>

.github/workflows/test.yml

@@ -0,0 +1,42 @@
+name: Continuous Integration
+
+on: [pull_request]
+
+jobs:
+  ci:
+    name: ci
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        scala: [2.12.10, 2.11.12]
+    container:
+      image: ucbbar/chisel3-tools
+      options: --user github --entrypoint /bin/bash
+    env:
+      CONTAINER_HOME: /home/github
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Setup Scala
+        uses: olafurpg/setup-scala@v10
+        with:
+          java-version: [email protected]
+      - name: Cache Scala
+        uses: coursier/cache-action@v5
+      - name: Test
+        run: sbt ++${{ matrix.scala }} test
+      - name: Binary compatibility
+        run: sbt ++${{ matrix.scala }} mimaReportBinaryIssues
+
+
+  # Sentinel job to simplify how we specify which checks need to pass in branch
+  # protection and in Mergify
+  #
+  # When adding new jobs, please add them to `needs` below
+  all_tests_passed:
+    name: "all tests passed"
+    needs: [ci]
+    runs-on: ubuntu-latest
+    steps:
+      - run: echo Success!

.mergify.yml

@@ -0,0 +1,107 @@
+pull_request_rules:
+- name: automatic squash-and-merge on CI success and review
+  conditions:
+  - status-success=all tests passed
+  - '#approved-reviews-by>=1'
+  - '#changes-requested-reviews-by=0'
+  - base=master
+  - label="Please Merge"
+  - label!="DO NOT MERGE"
+  - label!="bp-conflict"
+  actions:
+    merge:
+      method: squash
+      strict: smart
+      strict_method: merge
+- name: backport to 3.4.x
+  conditions:
+  - merged
+  - base=master
+  - milestone=3.4.x
+  actions:
+    backport:
+      branches:
+      - 3.4.x
+      ignore_conflicts: true
+      label_conflicts: bp-conflict
+    label:
+      add:
+      - Backported
+- name: backport to 3.3.x, 3.4.x
+  conditions:
+  - merged
+  - base=master
+  - milestone=3.3.x
+  actions:
+    backport:
+      branches:
+      - 3.3.x
+      - 3.4.x
+      ignore_conflicts: true
+      label_conflicts: bp-conflict
+    label:
+      add:
+      - Backported
+- name: backport to 3.2.x, 3.3.x, 3.4.x
+  conditions:
+  - merged
+  - base=master
+  - milestone=3.2.x
+  actions:
+    backport:
+      branches:
+      - 3.2.x
+      - 3.3.x
+      - 3.4.x
+      ignore_conflicts: true
+      label_conflicts: bp-conflict
+    label:
+      add:
+      - Backported
+- name: label Mergify backport PR
+  conditions:
+  - body~=This is an automated backport of pull request \#\d+ done by Mergify
+  actions:
+    label:
+      add:
+      - Backport
+- name: automatic squash-and-mege of 3.2.x backport PRs
+  conditions:
+  - status-success=all tests passed
+  - '#changes-requested-reviews-by=0'
+  - base=3.2.x
+  - label="Backport"
+  - label!="DO NOT MERGE"
+  - label!="bp-conflict"
+  actions:
+    merge:
+      method: squash
+      strict: smart
+      strict_method: merge
+- name: automatic squash-and-mege of 3.3.x backport PRs
+  conditions:
+  - status-success=all tests passed
+  - '#changes-requested-reviews-by=0'
+  - base=3.3.x
+  - label="Backport"
+  - label!="DO NOT MERGE"
+  - label!="bp-conflict"
+  actions:
+    merge:
+      method: squash
+      strict: smart
+      strict_method: merge
+- name: automatic squash-and-mege of 3.4.x backport PRs
+  conditions:
+  - status-success=all tests passed
+  - '#changes-requested-reviews-by=0'
+  - base=3.4.x
+  - label="Backport"
+  - label!="DO NOT MERGE"
+  - label!="bp-conflict"
+  actions:
+    merge:
+      method: squash
+      strict: smart
+      strict_method: merge
+