Add commands Github workflow

This is primarily for the /backport command that we can use to backport merged PRs.

Signed-off-by: Nic Cope <negz@rk0n.org>

.github/workflows/commands.yml

@@ -0,0 +1,92 @@
+name: Comment Commands
+
+on: issue_comment
+
+jobs:
+  points:
+    runs-on: ubuntu-18.04
+    if: startsWith(github.event.comment.body, '/points')
+
+    steps:
+    - name: Extract Command
+      id: command
+      uses: xt0rted/slash-command-action@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        command: points
+        reaction: "true"
+        reaction-type: "eyes"
+        allow-edits: "false"
+        permission-level: write
+    - name: Handle Command
+      uses: actions/github-script@v4
+      env:
+        POINTS: ${{ steps.command.outputs.command-arguments }}
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        script: |
+          const points = process.env.POINTS
+
+          if (isNaN(parseInt(points))) {
+            console.log("Malformed command - expected '/points <int>'")
+            github.reactions.createForIssueComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: context.payload.comment.id,
+              content: "confused"
+            })
+            return
+          }
+          const label = "points/" + points
+
+          // Delete our needs-points-label label.
+          try {
+            await github.issues.deleteLabel({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              name: ['needs-points-label']
+            })
+            console.log("Deleted 'needs-points-label' label.")
+          }
+          catch(e) {
+            console.log("Label 'needs-points-label' probably didn't exist.")
+          }
+
+          // Add our points label.
+          github.issues.addLabels({
+            issue_number: context.issue.number,
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            labels: [label]
+          })
+          console.log("Added '" + label + "' label.")
+
+  # NOTE(negz): See also backport.yml, which is the variant that triggers on PR
+  # merge rather than on comment.
+  backport:
+    runs-on: ubuntu-18.04
+    if: github.event.issue.pull_request && startsWith(github.event.comment.body, '/backport')
+    steps:
+    - name: Extract Command
+      id: command
+      uses: xt0rted/slash-command-action@v1
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}
+        command: backport
+        reaction: "true"
+        reaction-type: "eyes"
+        allow-edits: "false"
+        permission-level: write
+
+    - name: Checkout
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+
+    - name: Open Backport PR
+      uses: zeebe-io/backport-action@v0.0.4
+      with:
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        github_workspace: ${{ github.workspace }}
+        version: v0.0.4