CI: Dependabot for actions, cancel superseded runs

.github/dependabot.yml

@@ -0,0 +1,12 @@
+# Keeps the actions used by the workflows up to date: one pull request a week with
+# every new release. Actions referenced by branch, such as ghdl/setup-ghdl@main,
+# are not updated.
+version: 2
+updates:
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    groups:
+      actions:
+        patterns: ['*']

.github/workflows/docs.yml

@@ -9,6 +9,12 @@ on:
   pull_request:
   workflow_dispatch:
 
+# A new push cancels the run of the same branch or pull request still in progress.
+# On main and on tags every commit has a group of its own, so every run finishes.
+concurrency:
+  group: ${{ github.workflow }}-${{ (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/')) && github.sha || github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   docs:

.github/workflows/lint.yml

@@ -8,6 +8,12 @@ on:
   pull_request:
   workflow_dispatch:
 
+# A new push cancels the run of the same branch or pull request still in progress.
+# On main and on tags every commit has a group of its own, so every run finishes.
+concurrency:
+  group: ${{ github.workflow }}-${{ (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/')) && github.sha || github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   lint:

.github/workflows/python_bridge.yml

@@ -14,6 +14,12 @@ defaults:
   run:
     shell: bash
 
+# A new push cancels the run of the same branch or pull request still in progress.
+# On main and on tags every commit has a group of its own, so every run finishes.
+concurrency:
+  group: ${{ github.workflow }}-${{ (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/')) && github.sha || github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
 #