feat(copier): add support for using a PR Template in target repo

Author: cbullinger

examples-copier/configs/pr-template-example.yaml

@@ -0,0 +1,130 @@
+# Example: Using PR Templates from Target Repository
+# This configuration demonstrates the hybrid PR template approach
+
+source_repo: "myorg/source-repo"
+source_branch: "main"
+
+copy_rules:
+  # Example 1: Use target repo's PR template with appended copier info
+  - name: "use-target-template-with-append"
+    source_pattern:
+      type: "prefix"
+      pattern: "examples/"
+    targets:
+      - repo: "myorg/target-repo"
+        branch: "main"
+        path_transform: "code-examples/${relative_path}"
+        commit_strategy:
+          type: "pull_request"
+          pr_title: "Update code examples from ${source_repo}"
+          
+          # Fetch and use the PR template from the target repository
+          use_target_pr_template: true
+          
+          # Optional: Specify custom template path (defaults to .github/pull_request_template.md)
+          pr_template_path: ".github/pull_request_template.md"
+          
+          # Append copier-specific information after the template
+          pr_body_append: |
+            
+            ---
+            ## 🤖 Automated Copy Information
+            
+            This PR was automatically created by the examples-copier service.
+            
+            - **Source Repository**: ${source_repo}
+            - **Source Branch**: ${source_branch}
+            - **Source PR**: #${pr_number}
+            - **Source Commit**: ${commit_sha}
+            - **Files Updated**: ${file_count}
+            - **Copy Rule**: ${rule_name}
+            
+            ### Review Checklist
+            - [ ] Verify all files copied correctly
+            - [ ] Check for any breaking changes
+            - [ ] Run tests locally
+          
+          auto_merge: false
+
+  # Example 2: Use target repo's PR template without appending
+  - name: "use-target-template-only"
+    source_pattern:
+      type: "prefix"
+      pattern: "docs/"
+    targets:
+      - repo: "myorg/target-repo"
+        branch: "main"
+        path_transform: "documentation/${relative_path}"
+        commit_strategy:
+          type: "pull_request"
+          pr_title: "Update documentation from ${source_repo}"
+          
+          # Just use the target repo's template as-is
+          use_target_pr_template: true
+          
+          auto_merge: false
+
+  # Example 3: Traditional approach - define PR body in config
+  - name: "define-pr-body-in-config"
+    source_pattern:
+      type: "prefix"
+      pattern: "scripts/"
+    targets:
+      - repo: "myorg/target-repo"
+        branch: "main"
+        path_transform: "scripts/${relative_path}"
+        commit_strategy:
+          type: "pull_request"
+          pr_title: "Update scripts from ${source_repo}"
+          
+          # Define the entire PR body in the config
+          pr_body: |
+            ## Automated Update
+            
+            This PR updates scripts from the source repository.
+            
+            ### Details
+            - **Source**: ${source_repo}
+            - **PR**: #${pr_number}
+            - **Commit**: ${commit_sha}
+            - **Files**: ${file_count}
+            
+            ### Testing
+            Please verify that all scripts work as expected.
+          
+          auto_merge: false
+
+  # Example 4: Fallback behavior - template not found
+  - name: "template-with-fallback"
+    source_pattern:
+      type: "prefix"
+      pattern: "config/"
+    targets:
+      - repo: "myorg/target-repo"
+        branch: "main"
+        path_transform: "config/${relative_path}"
+        commit_strategy:
+          type: "pull_request"
+          pr_title: "Update config from ${source_repo}"
+          
+          # Try to use target template, but provide fallback via pr_body
+          use_target_pr_template: true
+          pr_template_path: ".github/pull_request_template.md"
+          
+          # This will be used if the template file is not found
+          pr_body: |
+            ## Configuration Update
+            
+            Automated update of configuration files.
+            
+            - Source: ${source_repo}
+            - Files: ${file_count}
+          
+          # This will be appended if the template IS found
+          pr_body_append: |
+            
+            ---
+            **Automated by**: examples-copier
+          
+          auto_merge: false
+

examples-copier/docs/CONFIGURATION-GUIDE.md

@@ -321,7 +321,7 @@ commit_strategy:
   pr_title: "Update ${lang} examples"
   pr_body: |
     Automated update of ${lang} examples
-    
+
     Files updated: ${file_count}
     Source: ${source_repo}
     PR: #${pr_number}
@@ -334,12 +334,50 @@ commit_strategy:
 - `pr_body` - (optional) PR body template
 - `auto_merge` - (optional) Auto-merge if checks pass (default: false)
 - `commit_message` - (optional) Commit message template
+- `use_target_pr_template` - (optional) Fetch PR template from target repo (default: false)
+- `pr_template_path` - (optional) Path to PR template in target repo (default: `.github/pull_request_template.md`)
+- `pr_body_append` - (optional) Additional content to append after the template
 
 **Use When:**
 - Changes require review
 - You want CI checks to run
 - Multiple approvers needed
 
+#### Using PR Templates from Target Repository
+
+You can configure the copier to use PR templates that exist in the target repository:
+
+```yaml
+commit_strategy:
+  type: "pull_request"
+  use_target_pr_template: true
+  pr_template_path: ".github/pull_request_template.md"  # Optional, this is the default
+  pr_body_append: |
+
+    ---
+    **Automated Copy Information:**
+    - Source: ${source_repo}
+    - PR: #${pr_number}
+    - Commit: ${commit_sha}
+    - Files: ${file_count}
+  auto_merge: false
+```
+
+**How it works:**
+1. The copier fetches the PR template file from the target repository
+2. Uses the template content as the PR body
+3. Optionally appends additional copier-specific information via `pr_body_append`
+4. If the template file is not found, falls back to using `pr_body` (if configured)
+
+**Template Variables:**
+Both `pr_body` and `pr_body_append` support template variables like `${source_repo}`, `${pr_number}`, `${file_count}`, etc.
+
+**Common PR Template Locations:**
+- `.github/pull_request_template.md` (default, hidden directory)
+- `pull_request_template.md` (root directory)
+- `docs/pull_request_template.md` (docs directory)
+- `.github/PULL_REQUEST_TEMPLATE/template_name.md` (multiple templates)
+
 ### Batch Commit
 
 Batches multiple files into fewer commits.