OSOE-144: Automatic comment on pull requests that have a merge conflict

.github/actions/check-merge-conflict/action.yml

@@ -0,0 +1,13 @@
+name: Check For Merge Conflict
+description: Checks for merge conflicts in in the current pull request.
+
+runs:
+  using: "composite"
+  steps:
+    - name: Check for merge conflict
+      # releases/2.x
+      uses: eps1lon/actions-label-merge-conflict@b8bf8341285ec9a4567d4318ba474fee998a6919
+      with:
+        repoToken: ${{ env.GITHUB_TOKEN }}
+        commentOnDirty: "This pull request has merge conflicts. Please resolve those before requesting a review."
+        dirtyLabel: "Merge Conflict"

.github/workflows/verify-submodule-pull-request.yml

@@ -16,3 +16,7 @@ jobs:
       uses: Lombiq/GitHub-Actions/.github/actions/verify-submodule-pull-request@dev
       with:
         title: ${{ github.event.pull_request.title }}
+    - name: Check for Merge Conflict in PR
+      uses: Lombiq/GitHub-Actions/.github/actions/check-merge-conflict@issue/OSOE-144
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

Docs/Actions.md

@@ -5,6 +5,7 @@ These actions can be invoked from a step in any other repository's workflow. The
 In addition to the below short explanations, check out the inline documentation of the action you want to use, especially its parameters.
 
 - `build-dotnet`: Builds all .NET solutions or projects in the given directory with optional static code analysis.
+- `check-merge-conflict`: Labels and comments on pull requests with merge conflicts.
 - `create-jira-issues-for-community-activities`: Creates Jira issues for community activities happening on GitHub, like issues, discussions, and pull requests being opened. Pull requests are only taken into account if they're not already related to a Jira issue (by starting their title with a Jira issue key).
 - `enable-corepack`: Enables [Node corepack](https://nodejs.org/docs/latest-v16.x/api/corepack.html) so any package manager can be used seamlessly.
 - `publish-nuget`: Publishes the content of the current directory as a NuGet package.

Docs/Workflows.md

@@ -57,6 +57,21 @@ jobs:
       timeout-minutes: 10
 ```
 
+## Check For Merge Conflict
+
+Labels and comments on Pull Requests with merge conflicts.
+
+```yaml
+name: Check For Merge Conflict
+
+on:
+  pull_request:
+
+jobs:
+  call-check-merge-conflict:
+    uses: Lombiq/GitHub-Actions/.github/workflows/check-merge-conflict.yml@dev
+```
+
 ## NuGet publish workflow
 
 Builds the project with the .NET SDK and publishes it as a NuGet package to the configured NuGet feed. Example _publish.yml_: