Merge branch 'appveyor-ci-improvements'

Cancel builds of non-latest PR version on AppVeyor and other minor
improvements.

See #2085.

.github/workflows/ci.yml

@@ -6,11 +6,13 @@ on:
     paths-ignore:
       - 'CHANGES*'
       - 'Doc/**'
+      - 'appveyor.yml'
   pull_request:
     branches: master
     paths-ignore:
       - 'CHANGES*'
       - 'Doc/**'
+      - 'appveyor.yml'
 
 jobs:
   build:

appveyor.yml

@@ -2,6 +2,12 @@ platform:
 - x86
 - x64
 
+skip_commits:
+  files:
+    - 'CHANGES*'
+    - 'Doc/**'
+    - '.github/**'
+
 environment:
   global:
     MAKEJOBS: 2
@@ -45,6 +51,14 @@ matrix:
   - SWIGLANG: python
     OSVARIANT: cygwin
 
+# Skip stale commits (pull requests only), see https://github.com/appveyor/ci/issues/38#issuecomment-70628826
+init:
+- ps: |
+    if ($env:APPVEYOR_PULL_REQUEST_NUMBER -and $env:APPVEYOR_BUILD_NUMBER -ne ((Invoke-RestMethod `
+        https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG/history?recordsNumber=50).builds | `
+        Where-Object pullRequestId -eq $env:APPVEYOR_PULL_REQUEST_NUMBER)[0].buildNumber) { `
+        throw "There are newer queued builds for this pull request, failing early." }
+
 install:
 - date /T & time /T
 - ps: >-