workflows: avoid running jobs when editing title etc.

We intend to use the edited event to react to base branch changes - but
before this change, we also ran those jobs on simple edits like title or
description.

While this works for some of the quicker jobs, it will not be
sustainable for all evaluation-related jobs. But evaluation needs to be
re-triggered on a base branch change as well, thus this change.

.github/workflows/check-format.yml

@@ -2,7 +2,6 @@ name: Check that files are formatted
 
 on:
   pull_request_target:
-    types: [opened, synchronize, reopened, edited]
 
 permissions: {}
 

.github/workflows/codeowners-v2.yml

@@ -24,7 +24,7 @@ name: Codeowners v2
 
 on:
   pull_request_target:
-    types: [opened, ready_for_review, synchronize, reopened, edited]
+    types: [opened, ready_for_review, synchronize, reopened]
 
 permissions: {}
 

.github/workflows/edited.yml

@@ -0,0 +1,49 @@
+# Some workflows depend on the base branch of the PR, but changing the base branch is not included in the default trigger events, which would be `opened`, `synchronize` or `reopened`.
+# Instead it causes an `edited` event.
+# Since `edited` is also triggered when PR title/body is changed, we use this wrapper workflow, to run the other workflows conditionally only.
+# There are already feature requests for adding a `base_changed` event:
+# - https://github.com/orgs/community/discussions/35058
+# - https://github.com/orgs/community/discussions/64119
+#
+# Instead of adding this to each workflow's pull_request_target event, we trigger this in a separate workflow.
+# This has the advantage, that we can actually skip running those jobs for simple edits like changing the title or description.
+# The actual trigger happens by closing and re-opening the pull request, which triggers the default pull_request_target events.
+# This is much simpler and reliable than other approaches.
+
+name: "Edited base branch"
+
+on:
+  pull_request_target:
+    types: [edited]
+
+permissions: {}
+
+jobs:
+  base:
+    name: Trigger jobs
+    runs-on: ubuntu-24.04
+    if: github.event.changes.base.ref.from && github.event.changes.base.ref.from != github.event.pull_request.base.ref
+    steps:
+      # Use a GitHub App to create the PR so that CI gets triggered
+      # The App is scoped to Repository > Contents and Pull Requests: write for Nixpkgs
+      # We only need Pull Requests: write here, but the app is also used for backports.
+      - uses: actions/create-github-app-token@df432ceedc7162793a195dd1713ff69aefc7379e # v2.0.6
+        id: app-token
+        with:
+          app-id: ${{ vars.NIXPKGS_CI_APP_ID }}
+          private-key: ${{ secrets.NIXPKGS_CI_APP_PRIVATE_KEY }}
+          permission-pull-requests: write
+
+      - env:
+          GH_TOKEN: ${{ steps.app-token.outputs.token }}
+          REPOSITORY: ${{ github.repository }}
+          NUMBER: ${{ github.event.number }}
+        run: |
+          gh api \
+            --method PATCH \
+            /repos/"$REPOSITORY"/pulls/"$NUMBER" \
+            -f "state=closed"
+          gh api \
+            --method PATCH \
+            /repos/"$REPOSITORY"/pulls/"$NUMBER" \
+            -f "state=open"

.github/workflows/labels.yml

@@ -7,7 +7,6 @@ name: "Label PR"
 
 on:
   pull_request_target:
-    types: [edited, opened, synchronize, reopened]
 
 permissions:
   contents: read

.github/workflows/nixpkgs-vet.yml

@@ -7,11 +7,6 @@ name: Vet nixpkgs
 
 on:
   pull_request_target:
-    # This workflow depends on the base branch of the PR, but changing the base branch is not included in the default trigger events, which would be `opened`, `synchronize` or `reopened`.
-    # Instead it causes an `edited` event, so we need to add it explicitly here.
-    # While `edited` is also triggered when the PR title/body is changed, this PR action is fairly quick, and PRs don't get edited **that** often, so it shouldn't be a problem.
-    # There is a feature request for adding a `base_changed` event: https://github.com/orgs/community/discussions/35058
-    types: [opened, synchronize, reopened, edited]
 
 permissions: {}
 

.github/workflows/no-channel.yml

@@ -2,8 +2,6 @@ name: "No channel PR"
 
 on:
   pull_request_target:
-    # Re-run should be triggered when the base branch is updated, instead of silently failing
-    types: [opened, synchronize, reopened, edited]
 
 permissions: {}