Add merge-pr.py helper script

This adds a helper script to generate merge commits that are nicer than
the default Github one.

scripts/merge-pr.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+#
+# A script to merge Limbo pull requests with a nice merge commit.
+#
+# Requirements:
+#
+# ```
+# pip install PyGithub
+# ```
+
+import sys
+import re
+from github import Github
+import os
+import subprocess
+
+def run_command(command):
+    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=True)
+    output, error = process.communicate()
+    return output.decode('utf-8').strip(), error.decode('utf-8').strip(), process.returncode
+
+def get_pr_info(repo, pr_number):
+    pr = repo.get_pull(int(pr_number))
+    author = pr.user
+    author_name = author.name if author.name else author.login
+    return {
+        'number': pr.number,
+        'title': pr.title,
+        'author': author_name,
+        'head': pr.head.ref,
+        'body': pr.body.strip() if pr.body else ''
+    }
+
+def merge_pr(pr_number):
+    # GitHub authentication
+    token = os.getenv('GITHUB_TOKEN')
+
+    g = Github(token)
+    
+    # Get the repository
+    repo_name = os.getenv('GITHUB_REPOSITORY')
+    if not repo_name:
+        print("Error: GITHUB_REPOSITORY environment variable not set")
+        sys.exit(1)
+    
+    repo = g.get_repo(repo_name)
+    
+    # Get PR information
+    pr_info = get_pr_info(repo, pr_number)
+    
+    # Format commit message
+    commit_message = f"Merge '{pr_info['title']}' from {pr_info['author']}\n\n{pr_info['body']}\n\nCloses #{pr_info['number']}"
+    
+    # Fetch the PR branch
+    cmd = f"git fetch origin pull/{pr_number}/head:{pr_info['head']}"
+    output, error, returncode = run_command(cmd)
+    if returncode != 0:
+        print(f"Error fetching PR branch: {error}")
+        sys.exit(1)
+    
+    # Checkout main branch
+    cmd = "git checkout main"
+    output, error, returncode = run_command(cmd)
+    if returncode != 0:
+        print(f"Error checking out main branch: {error}")
+        sys.exit(1)
+    
+    # Merge the PR
+    cmd = f"git merge --no-ff {pr_info['head']} -m \"{commit_message}\""
+    output, error, returncode = run_command(cmd)
+    if returncode != 0:
+        print(f"Error merging PR: {error}")
+        sys.exit(1)
+    
+    print("Pull request merged successfully!")
+    print(f"Merge commit message:\n{commit_message}")
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print("Usage: python merge_pr.py <pr_number>")
+        sys.exit(1)
+    
+    pr_number = sys.argv[1]
+    if not re.match(r'^\d+$', pr_number):
+        print("Error: PR number must be a positive integer")
+        sys.exit(1)
+    
+    merge_pr(pr_number)