Enable automatic labeling of PRs via Actions (#3431)

* Automatically label PRs based on the file paths

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Enable prow-like commands

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Require filling in the PR template

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Update contributor docs to reference PR template

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Expand checklist and ask for issue number on PRs

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Document why we're not enabling /lgtm yet

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

* Combine PR assignment and labeling workflow

Signed-off-by: Nolan Brubaker <brubakern@vmware.com>

.github/workflows/auto_assign_prs.yml

@@ -1,16 +1,24 @@
-name: 'Auto Assign PR Reviewers'
+name: "Auto Assign PR Reviewers"
 # pull_request_target means that this will run on pull requests, but in the context of the base repo.
 # This should mean PRs from forks are supported.
-on: 
+on:
   pull_request_target:
     types: [opened, reopened, synchronize, ready_for_review]
 
-
-jobs: 
+jobs:
+  # Automatically assigns reviewers and owner
   add-reviews:
     runs-on: ubuntu-latest
     steps:
       - uses: kentaro-m/auto-assign-action@v1.1.1
-        with: 
+        with:
           configuration-path: ".github/auto_assign.yml"
-          repo-token: '${{ secrets.GITHUB_TOKEN }}'
+          repo-token: "${{ secrets.GITHUB_TOKEN }}"
+  # Automatically labels PRs based on file globs in the change.
+  triage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/labeler@main
+        with:
+          repo-token: "${{ secrets.GITHUB_TOKEN }}"
+          configuration-path: .github/labels.yaml

.github/workflows/prow-action.yml

@@ -0,0 +1,20 @@
+# Adds support for prow-like commands
+# Uses .github/labels.yaml to define areas and kinds
+name: "Prow github actions"
+on:
+  issue_comment:
+    types: [created]
+
+jobs:
+  execute:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: jpmcb/prow-github-actions@v1
+        with:
+          # Only support /kind command for now.
+          # TODO: before allowing the /lgtm command, see if we can block merging if changelog labels are missing.
+          prow-commands: "/area
+            /kind
+            /cc
+            /uncc"
+          github-token: "${{ secrets.GITHUB_TOKEN }}"