ci: Enable coverage on main and all PRs

.codecov.yml

@@ -1,8 +1,34 @@
+codecov:
+  ignore:
+    - "linkerd/app/integration/src/**"
+    - "**/src/gen/**"
+    - "tools/**"
+
 coverage:
-  # Disable statuses until we sort out coverage more broadly. This is noisy as
-  # it is.
+  precision: 2
+  round: down
+  range: "70...100"
+
   status:
     project:
-      default: false
+      default:
+        target: auto
+        threshold: 2%
+        if_not_found: success
+        if_ci_failed: error
+        paths:
+          - "!linkerd/app/integration/src/**"
+          - "!**/src/gen/**"
+          - "!tools/**"
+
     patch:
-      default: false
+      default:
+        target: auto
+        threshold: 1%
+        if_not_found: success
+        if_ci_failed: error
+
+comment:
+  layout: "header, diff, files, footer"
+  behavior: default
+  require_changes: false

.github/workflows/coverage.yml

@@ -4,13 +4,18 @@ permissions:
   contents: read
 
 on:
+  # We run coverage on main so that PRs can have a meaninful comparison that
+  # doesn't lag a whole day.
+  push:
+    branches:
+      - main
+
+  # Coverage runs on all code changes (as well as changes to the workflow).
   pull_request:
     paths:
       - .codecov.yml
       - .github/workflows/coverage.yml
-  schedule:
-    # Run daily at 11AM UTC (3AM PST).
-    - cron: '0 11 * * *'
+      - '**/*.rs'
 
 env:
   CARGO_INCREMENTAL: 0
@@ -19,6 +24,18 @@ env:
   RUSTUP_MAX_RETRIES: 10
 
 jobs:
+  # Cancel any previous runs of this workflow so coverage runs don't back up,
+  # especially on main (i.e. after merging several PRs).
+  cleanup:
+    runs-on: ubuntu-latest
+    permissions:
+      actions: write
+    steps:
+      - uses: styfle/cancel-workflow-action@01ce38bf961b4e243a6342cbade0dbc8ba3f0432
+        with:
+          all_but_latest: true
+          access_token: ${{ github.token }}
+
   test:
     name: codecov
     runs-on: ubuntu-latest