github-actions: Auto-backporting

An implementation of semi-automating the backporting
process.

This implementation has two steps:
1. Checking whether any associated issues are marked as bugs

   If they do, mark with `auto-backport` label

2. On a successful merge, if there is a `auto-backport` label  and there
   are any tags of `backport-to-BRANCHNAME`, it calls an action that
   cherry-picks the commits in the PR and automatically creates a PR to
   those branches.

This action uses https://github.com/sqren/backport-github-action

Fixes #3618

Signed-off-by: Derek Lee <derlee@redhat.com>

.github/workflows/add-backport-label.yaml

@@ -0,0 +1,100 @@
+name: Add backport label
+
+on:
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - edited
+      - labeled
+      - unlabeled
+
+jobs:
+  check-issues:
+    if: ${{ github.event.label.name != 'auto-backport' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code to allow hub to communicate with the project
+        if: ${{ !contains(github.event.pull_request.labels.*.name, 'force-skip-ci') }}
+        uses: actions/checkout@v3
+
+      - name: Install hub extension script
+        run: |
+          pushd $(mktemp -d) &>/dev/null
+          git clone --single-branch --depth 1 "https://github.com/kata-containers/.github" && cd .github/scripts
+          sudo install hub-util.sh /usr/local/bin
+          popd &>/dev/null
+
+      - name: Determine whether to add label 
+        if: ${{ !contains(github.event.pull_request.labels.*.name, 'force-skip-ci') }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          CONTAINS_AUTO_BACKPORT: ${{ contains(github.event.pull_request.labels.*.name, 'auto-backport') }}
+        id: add_label
+        run: |
+          pr=${{ github.event.pull_request.number }}
+          linked_issue_urls=$(hub-util.sh \
+            list-issues-for-pr "$pr" |\
+            grep -v "^\#"  |\
+            cut -d';' -f3 || true)
+          [ -z "$linked_issue_urls" ] && {
+            echo "::error::No linked issues for PR $pr"
+            exit 1
+          }
+          has_bug=false
+          for issue_url in $(echo "$linked_issue_urls")
+          do
+            issue=$(echo "$issue_url"| awk -F\/ '{print $NF}' || true)
+            [ -z "$issue" ] && {
+              echo "::error::Cannot determine issue number from $issue_url for PR $pr"
+              exit 1
+            }
+            labels=$(hub-util.sh list-labels-for-issue "$issue")
+            
+            label_names=$(echo $labels | jq -r '.[].name' || true)
+            if [[ "$label_names" =~ "bug" ]]; then
+              has_bug=true
+              break
+            fi
+          done
+
+          has_backport_needed_label=${{ contains(github.event.pull_request.labels.*.name, 'needs-backport') }}
+          has_no_backport_needed_label=${{ contains(github.event.pull_request.labels.*.name, 'no-backport-needed') }}
+
+          echo "::set-output name=add_backport_label::false"
+          if [ $has_backport_needed_label  = true ] || [ $has_bug  = true ]; then
+            if [[ $has_no_backport_needed_label = false ]]; then
+              echo "::set-output name=add_backport_label::true"
+            fi
+          fi
+
+          # Do not spam comment, only if auto-backport label is going to be newly added.
+          echo "::set-output name=auto_backport_added::$CONTAINS_AUTO_BACKPORT"
+
+      - name: Add comment
+        if: ${{ !contains(github.event.pull_request.labels.*.name, 'force-skip-ci') && steps.add_label.outputs.add_backport_label == 'true' && steps.add_label.outputs.auto_backport_added == 'false' }}
+        uses: actions/github-script@v6
+        with:
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: 'This issue has been marked for auto-backporting. Add label(s) backport-to-BRANCHNAME to backport to them'
+            })
+
+      # Allow label to be removed by adding no-backport-needed label
+      - name: Remove auto-backport label
+        if: ${{ !contains(github.event.pull_request.labels.*.name, 'force-skip-ci') && steps.add_label.outputs.add_backport_label == 'false' }}
+        uses: andymckay/labeler@e6c4322d0397f3240f0e7e30a33b5c5df2d39e90
+        with:
+          remove-labels: "auto-backport"
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Add auto-backport label
+        if: ${{ !contains(github.event.pull_request.labels.*.name, 'force-skip-ci') && steps.add_label.outputs.add_backport_label == 'true' }}
+        uses: andymckay/labeler@e6c4322d0397f3240f0e7e30a33b5c5df2d39e90
+        with:
+          add-labels: "auto-backport"
+          repo-token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/auto-backport.yaml

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+on:
+  pull_request_target:
+    types: ["labeled", "closed"]
+
+jobs:
+  backport:
+    name: Backport PR
+    runs-on: ubuntu-latest
+    if: |
+      github.event.pull_request.merged == true
+      && contains(github.event.pull_request.labels.*.name, 'auto-backport')
+      && (
+        (github.event.action == 'labeled' && github.event.label.name == 'auto-backport')
+        || (github.event.action == 'closed')
+      )
+    steps:
+      - name: Backport Action
+        uses: sqren/backport-github-action@v8.9.2
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          auto_backport_label_prefix: backport-to-
+
+      - name: Info log
+        if: ${{ success() }}
+        run: cat /home/runner/.backport/backport.info.log
+        
+      - name: Debug log
+        if: ${{ failure() }}
+        run: cat /home/runner/.backport/backport.debug.log