Add: [checkout-pull-request] action to checkout all commits of a sing…

…le Pull Request (#26)

README.md

@@ -9,6 +9,7 @@ As GitHub Actions doesn't allow to include workflows of other projects, this is
 
 - [checkout](checkout/): Checkout tags and submodules; complements `actions/checkout`.
 - [checkout-dispatch](checkout-dispatch/): Checkout from `remote_dispatch` with `publish_latest_tag`.
+- [checkout-pull-request](checkout-pull-request/): Checkout all commits of a Pull Request.
 - [deploy-aws](deploy-aws/): Deploy new Docker image to AWS.
 - [deployments-create](deployments-create/): Create GitHub Deployments.
 - [deployments-update](deployments-update/): Update GitHub Deployments status.

checkout-pull-request/README.md

@@ -0,0 +1,21 @@
+# OpenTTD - Checkout all commits of a Pull Request
+
+The default `actions/checkout` only checks out the merge commit of a
+Pull Request. This means that on `HEAD` is the merge commit, on `HEAD^` is the
+base branch, and on `HEAD^2` are the commits of the Pull Request. Sometimes we
+need all the commits of the Pull Request available to us, but the default
+fetch-depth only give these three commits.
+
+This action tries in a smart way to fetch the full history of a Pull Request,
+by fetching more and more commits till `HEAD^` and `HEAD^2` have a common parent.
+The log between those are all the commits the Pull Request introduce.
+
+## Usage
+
+First make sure to use `actions/checkout` to get the repository. Use a
+`fetch-depth` of 4.
+This action should be called directly after that.
+
+```yaml
+- uses: openttd/actions/checkout-pull-request@v2
+```

checkout-pull-request/action.yml

@@ -0,0 +1,7 @@
+name: 'OpenTTD - Checkout Pull Request'
+description: 'Checkout action to get the full history of a Pull Request'
+author: 'OpenTTD'
+inputs: {}
+runs:
+  using: 'node12'
+  main: 'dist/index.js'