feat: initial commitmaster

1 files changed, 217 insertions, 0 deletions

diff --git a/git_merge_report.py b/git_merge_report.py
new file mode 100644
index 0000000..c351ece
--- /dev/null
+++ b/git_merge_report.py
@@ -0,0 +1,217 @@
+#!/usr/bin/env python3
+"""
+git_merge_report.py
+
+Merges a remote branch into a local branch, and builds a summary report of
+the merge (divergence point, commit count, line changes, file changes).
+The rendered summary is used as the merge commit message.
+
+Usage:
+    python git_merge_report.py <local_branch> <remote_branch> (-m "message" | -f path/to/message.txt)
+
+Examples:
+    python git_merge_report.py main feature/login -m "Add login flow"
+    python git_merge_report.py main feature/login -f commit_msg.txt
+    python git_merge_report.py main feature/login -m "Add login flow" --dry-run
+"""
+
+import argparse
+import re
+import subprocess
+import sys
+from datetime import datetime, timezone
+
+TEMPLATE = """Merge {remote} into {local}:
+Merge commit message:
+{msg}
+
+-----------------------------BEGIN SUMMARY OF MERGE----------------------------
+Merging {n} commits into {local}.
+{remote} diverged from {local} at commit {commit_hash} {days} days ago
+Commit makes {add_chg} additions, {rem_chg} deletions
+Commit adds {add_file} files, removes {rem_file} files
+------------------------------END SUMMARY OF MERGE-----------------------------
+"""
+
+
+class GitError(RuntimeError):
+    pass
+
+
+def run_git(args, repo="."):
+    """Run a git command and return stripped stdout. Raises GitError on failure."""
+    try:
+        result = subprocess.run(
+            ["git", "-C", repo] + args,
+            check=True,
+            capture_output=True,
+            text=True,
+        )
+        return result.stdout.strip()
+    except subprocess.CalledProcessError as e:
+        raise GitError(
+            f"git {' '.join(args)} failed:\n{e.stderr.strip()}"
+        ) from e
+    except FileNotFoundError as e:
+        raise GitError("git executable not found on PATH") from e
+
+
+def verify_branch_exists(branch, repo="."):
+    try:
+        run_git(["rev-parse", "--verify", "--quiet", branch], repo)
+    except GitError:
+        raise GitError(f"Branch '{branch}' does not exist in this repository.")
+
+
+def get_merge_base(local, remote, repo="."):
+    """Commit where remote diverged from local."""
+    return run_git(["merge-base", local, remote], repo)
+
+
+def get_commit_date(commit_hash, repo="."):
+    """ISO8601 commit date of a commit, as a timezone-aware datetime."""
+    iso = run_git(["show", "-s", "--format=%cI", commit_hash], repo)
+    return datetime.fromisoformat(iso)
+
+
+def days_since(commit_hash, repo="."):
+    commit_dt = get_commit_date(commit_hash, repo)
+    now = datetime.now(timezone.utc)
+    delta = now - commit_dt.astimezone(timezone.utc)
+    return delta.days
+
+
+def get_commit_count(local, remote, repo="."):
+    """Number of commits on remote not yet on local (i.e. being merged in)."""
+    out = run_git(["rev-list", "--count", f"{local}..{remote}"], repo)
+    return int(out)
+
+
+def get_diff_shortstat(local, remote, repo="."):
+    """Lines added/removed between merge-base(local,remote) and remote."""
+    out = run_git(["diff", "--shortstat", f"{local}...{remote}"], repo)
+    added = removed = 0
+    if out:
+        add_match = re.search(r"(\d+) insertion", out)
+        rem_match = re.search(r"(\d+) deletion", out)
+        if add_match:
+            added = int(add_match.group(1))
+        if rem_match:
+            removed = int(rem_match.group(1))
+    return added, removed
+
+
+def get_file_changes(local, remote, repo="."):
+    """Count of files added (A) and removed (D) between local and remote."""
+    out = run_git(["diff", "--name-status", f"{local}...{remote}"], repo)
+    added_files = removed_files = 0
+    for line in out.splitlines():
+        if not line.strip():
+            continue
+        status = line.split("\t", 1)[0]
+        # status can be 'A', 'D', 'M', or rename/copy scores like 'R100'
+        if status.startswith("A"):
+            added_files += 1
+        elif status.startswith("D"):
+            removed_files += 1
+    return added_files, removed_files
+
+
+def read_message(args):
+    if args.message is not None:
+        return args.message
+    with open(args.message_file, "r", encoding="utf-8") as f:
+        return f.read().strip()
+    return "None"
+
+
+def build_summary(local, remote, msg, repo="."):
+    merge_base_hash = get_merge_base(local, remote, repo)
+    short_hash = run_git(["rev-parse", "--short", merge_base_hash], repo)
+    n_days = days_since(merge_base_hash, repo)
+    n_commits = get_commit_count(local, remote, repo)
+    add_chg, rem_chg = get_diff_shortstat(local, remote, repo)
+    add_file, rem_file = get_file_changes(local, remote, repo)
+
+    summary = TEMPLATE.format(
+        remote=remote,
+        local=local,
+        msg=msg,
+        n=n_commits,
+        commit_hash=short_hash,
+        days=n_days,
+        add_chg=add_chg,
+        rem_chg=rem_chg,
+        add_file=add_file,
+        rem_file=rem_file,
+    )
+    return summary
+
+
+def perform_merge(local, remote, commit_message, repo="."):
+    run_git(["checkout", local], repo)
+    run_git(["merge", "--no-ff", remote, "-m", commit_message], repo)
+
+
+def parse_args(argv=None):
+    parser = argparse.ArgumentParser(
+        description="Merge a remote branch into a local branch and report a summary."
+    )
+    parser.add_argument("local_branch", help="Branch to merge INTO")
+    parser.add_argument("remote_branch", help="Branch to merge (source)")
+
+    msg_group = parser.add_mutually_exclusive_group(required=True)
+    msg_group.add_argument(
+        "-m", "--message", help="Merge commit message, given directly as text"
+    )
+    msg_group.add_argument(
+        "-f",
+        "--message-file",
+        help="Path to a file containing the merge commit message",
+    )
+
+    parser.add_argument(
+        "--repo",
+        default=".",
+        help="Path to the git repository (default: current directory)",
+    )
+    parser.add_argument(
+        "--dry-run",
+        action="store_true",
+        help="Only print the summary report; do not perform the actual merge",
+    )
+
+    return parser.parse_args(argv)
+
+
+def main(argv=None):
+    args = parse_args(argv)
+    repo = args.repo
+
+    try:
+        verify_branch_exists(args.local_branch, repo)
+        verify_branch_exists(args.remote_branch, repo)
+
+        msg = read_message(args)
+        summary = build_summary(args.local_branch, args.remote_branch, msg, repo)
+
+        print(summary)
+
+        if args.dry_run:
+            print("[dry-run] No merge performed.")
+            return 0
+
+        perform_merge(args.local_branch, args.remote_branch, summary, repo)
+        print(f"Merge complete: '{args.remote_branch}' merged into '{args.local_branch}'.")
+        return 0
+
+    except GitError as e:
+        print(f"Error: {e}", file=sys.stderr)
+        return 1
+    except FileNotFoundError:
+        print(f"Error: message file '{args.message_file}' not found.", file=sys.stderr)
+        return 1
+
+
+if __name__ == "__main__":
+    sys.exit(main())