Add merge.py

This script can be used for merging from one release branch of SKC into
the next.

tools/merge.py

@@ -0,0 +1,116 @@
+#!/usr/bin/python3
+
+DESCRIPTION = """
+This script merges one release branch of SKC into another.
+
+Example 1: Merge stackhpc/yoga into stackhpc/zed:
+
+    merge.py yoga zed
+
+Example 2: Merge the branch created in example 1 into stackhpc/2023.1:
+
+    merge.py zed 2023.1 zed-yoga-merge
+
+Example 3: Continue after manually resolving merge conflicts seen in example 2:
+
+    merge.py zed 2023.1 zed-yoga-merge --continue
+
+"""
+
+import argparse
+import os
+from subprocess import check_call, check_output
+import sys
+
+
+def command(cmd):
+    print("Running:", cmd)
+    check_call(cmd)
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description=DESCRIPTION, formatter_class=argparse.RawDescriptionHelpFormatter)
+    #"Merge one branch of SKC into the next")
+    parser.add_argument("previous", type=str, help="The previous version")
+    parser.add_argument("current", type=str, help="The current version")
+    parser.add_argument("previous_branch", type=str, nargs="?", default=None, help="Optional branch to use as the previous release. Allows merging multiple branches in parallel.")
+    parser.add_argument("--continue", dest="cont", action="store_true", help="Continue after merge conflicts have been resolved.")
+    parser.add_argument("--remote", type=str, default="origin", help="Git remote")
+    return parser.parse_args()
+
+
+def fetch(args):
+    command(["git", "fetch", args.remote])
+
+
+def checkout(args):
+    merge_branch = f"{args.current}-{args.previous}-merge"
+    current_branch = f"{args.remote}/stackhpc/{args.current}"
+    command(["git", "checkout", "-B", merge_branch, current_branch])
+
+
+def update_submodules():
+    command(["git", "submodule", "update"])
+
+
+def merge_in_progress():
+    repo_root = check_output(["git", "rev-parse", "--show-toplevel"])
+    repo_root = repo_root.decode().strip()
+    return os.path.isfile(os.path.join(repo_root, ".git", "MERGE_HEAD"))
+
+
+def uncommitted_changes():
+    unstaged = check_output(["git", "diff"])
+    staged = check_output(["git", "diff", "--cached"])
+    return unstaged or staged
+
+
+def continue_merge():
+    if merge_in_progress():
+        command(["git", "merge", "--continue"])
+    else:
+        print("No merge in progress")
+
+
+def merge(args):
+    if args.previous_branch:
+        previous_branch = args.previous_branch
+    else:
+        previous_branch = f"{args.remote}/stackhpc/{args.previous}"
+    commit_message = f"Merge stackhpc/{args.previous} into stackhpc/{args.current}"
+    command(["git", "merge", previous_branch, "-m", commit_message])
+
+
+def show_diff(args):
+    print("Proposed changes:")
+    current_branch = f"{args.remote}/stackhpc/{args.current}"
+    command(["git", "diff", current_branch])
+
+
+def create_pr(args):
+    current_branch = f"stackhpc/{args.current}"
+    pr_title = f"{args.current}: {args.previous} merge"
+    command(["gh", "pr", "create", "-f", "-a", "@me", "-B", current_branch, "-t", pr_title])
+
+
+def main():
+    args = parse_args()
+    if args.cont:
+        continue_merge()
+    else:
+        if merge_in_progress():
+            print("Merge in progress - did you miss the --continue argument?")
+            sys.exit(1)
+        if uncommitted_changes():
+            print("You have uncommitted changes - aborting")
+            sys.exit(1)
+        fetch(args)
+        checkout(args)
+        update_submodules()
+        merge(args)
+    show_diff(args)
+    create_pr(args)
+
+
+if __name__ == "__main__":
+    main()