Add an action to perform automatic releases

This action automatically does the following every thursday at 9:00 AM:

* Create a commit that increments the last number of CBMC_VERSION
  in src/config.inc
* Perform a release tagged with the new CBMC_VERSION number

This only saves us a tiny bit of work right now, but we’ll add actions to
automatically create and upload binary artifacts for these releases soon.

Author: hannes-steffenhagen-diffblue

.github/workflows/regular-release.yaml

@@ -0,0 +1,57 @@
+on:
+  schedule:
+#            ┌───────────── minute (0 - 59)
+#            │ ┌───────────── hour (0 - 23)
+#            │ │ ┌───────────── day of the month (1 - 31)
+#            │ │ │ ┌───────────── month (1 - 12 or JAN-DEC)
+#            │ │ │ │ ┌───────────── day of the week (0 - 6 or SUN-SAT)
+#            │ │ │ │ │
+#            │ │ │ │ │
+#            │ │ │ │ │
+    - cron: '0 9 * * THU'
+      # ^ this means 9:00 AM every thursday
+      # I can’t figure out the right syntax
+      # for ‘every other thursday’
+
+jobs:
+  bump-cbmc-version:
+    runs-on: ubuntu-20.04
+    outputs:
+      CBMC_VERSION: ${{steps.cbmc_version_number.outputs.CBMC_VERSION}}
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive
+      - name: Get new CBMC version number
+        id: cbmc_version_number
+        run: |
+          NEW_CBMC_VERSION=$(grep '^CBMC_VERSION =' src/config.inc | cut -d = -f 2 | scripts/increment_version.sh)
+          echo ::set-env name=CBMC_VERSION::$NEW_CBMC_VERSION
+          echo ::set-output name=CBMC_VERSION::$NEW_CBMC_VERSION
+      - name: Update CBMC version
+        run: |
+          sed -i "s/CBMC_VERSION = .*/CBMC_VERSION = $CBMC_VERSION/" src/config.inc
+      - name: Set git identity to github bot
+        run: |
+          git config --local user.name github-actions
+          git config --local user.email "[email protected]"
+      - name: Commit changes
+        run: |
+          git commit -a -m "Bump version to $CBMC_VERSION"
+      - name: Push changes
+        run: |
+          git push
+  perform-release:
+    needs: bump-cbmc-version
+    runs-on: ubuntu-20.04
+    steps:
+      - uses: actions/checkout@v2
+      - name: Create release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: cbmc-${{needs.bump-cbmc-version.outputs.CBMC_VERSION}}
+          release_name: cbmc-${{needs.bump-cbmc-version.outputs.CBMC_VERSION}}
+          draft: false
+          prerelease: true

scripts/increment_version.sh

@@ -0,0 +1,5 @@
+read -r version_line
+major=$(echo $version_line | cut -d . -f 1)
+minor=$(echo $version_line | cut -d . -f 2)
+patch=$(echo $version_line | cut -d . -f 3)
+echo "$major.$minor.$(expr $patch + 1)"