2 files changed, 811 insertions, 0 deletions

diff --git a/tools/tools/git/git-mfc b/tools/tools/git/git-mfc
new file mode 100755
index 000000000000..181432fad523
--- /dev/null
+++ b/tools/tools/git/git-mfc
@@ -0,0 +1,523 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2025 Klara, Inc.
+# Copyright (c) 2026 Mark Johnston <markj@FreeBSD.org>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# git-mfc - Helper command for MFCing commits to stable or release branches.
+#
+
+import argparse
+import datetime
+import os
+import re
+import subprocess
+import sys
+
+
+def err(code, msg):
+    print(os.path.basename(sys.argv[0]) + ': ' + msg, file=sys.stderr)
+    sys.exit(code)
+
+
+try:
+    import git
+except ImportError:
+    err(1, "gitpython module missing; install it with pip or the devel/py-gitpython package")
+
+
+def commit_summary(commit):
+    return f'{commit.hexsha} ("{commit.summary}")'
+
+
+def origin_branch():
+    """
+    Determine the default origin branch by parsing sys/conf/newvers.sh.
+    """
+    newvers = 'sys/conf/newvers.sh'
+    if not os.path.exists(newvers):
+        err(1, f"{newvers} not found; use --origin to specify the upstream branch")
+
+    revision = None
+    branch = None
+    with open(newvers) as f:
+        for line in f:
+            m = re.match(r'^REVISION="([^"]+)"', line)
+            if m:
+                revision = m.group(1)
+            m = re.match(r'^BRANCH="([^"]+)"', line)
+            if m:
+                branch = m.group(1)
+
+    if branch is None:
+        err(1, f"could not determine BRANCH from {newvers}")
+    if branch == "CURRENT":
+        err(1, "this is a CURRENT tree, we do not MFC to CURRENT")
+    if branch == "STABLE":
+        return "main"
+    if re.match(r'^RELEASE(-p\d+)?$', branch):
+        if revision is None:
+            err(1, f"could not determine REVISION from {newvers}")
+        major = revision.split('.')[0]
+        return f"stable/{major}"
+
+    err(1, f"unexpected BRANCH value '{branch}' in {newvers}")
+
+
+def fixes(repo, commit, warn=False):
+    """
+    Look at the commit's log message and return a list of commits that it fixes.
+
+    Hard-code a bunch of special cases in the src repo, where the fixes tag is
+    valid but malformed somehow.
+    """
+    special = {
+        "a693d17b9985a03bd9b5108e890d669005ab41eb": ["8a42005d1e491932666eb9f0be3e70ea1a28a3f7"],
+        "a04ca1c229195c7089b878a94fbe76505ea693b5": ["93b7818226cf5270646725805b4a8c17a1ad3761"],
+        "852088f6af6c5cd44542dde72aa5c3f4c4f9353c": ["b5fb9ae6872c499f1a02bec41f48b163a73a2aaa"],
+        "9c5d7e4a0c02bc45b61f565586da2abcc65d70fa": ["bec000c9c1ef409989685bb03ff0532907befb4a"],
+        "894cb08f0d3656fdb81f4d89085bedc4235f3cb6": ["5678d1d98a348f315453555377ccb28821a2ffcd"],
+        "cbddb2f02c7687d1039abcffd931e94e481c11a5": ["0118b0c8e58a438a931a5ce1bf8d7ae6208cc61b"],
+        "e9da71cd35d46ca13da4396d99e0af1703290e68": [],
+        "43cd6bbba053f02999d846ef297655ebec2d218b": ["38cbdae33b7c3f772845c06f52b86c0ddeab6a17"],
+        "94efe9f91be7f3aa501983716db5a4378282a734": ["7520b88860d7a79432e12ffcc47056844518bb62"],
+        "b332adfa96218148dfbb936a9c09d00484c868e3": ["7520b88860d7a79432e12ffcc47056844518bb62"],
+        "b911f504005df67f8c25f9b2f817c16588cd309c": ["801fb66a7e34c340f23d82f2b375feee4bd87df4"],
+        "3d37e7e5f540f513ab1d8fa61d9208c43b889401": ["fb9baa9b2045a193a3caf0a46b5cac5ef7a84b61"],
+        "0912408a281f203c43d0b3f73c38117336588342": ["9e33a616939fcff87f7539e3c41323deca5c74ce"],
+        "c036339ddf0cf80164f41ea31f1d8d27f4a068a9": ["a305b20ead13bb29880e15ff20c3bb83b5397a82"],
+        "9b56dfd27c64fcaf5dfbaa1eb3e2bd2b163fa56c": [],
+        "ab92cab02633580f763a38a329a5b25050bb4fbf": [],
+        "28fdb212adc0431fff683749a1307038e25ff58e": [],
+        "811912c46b5886f1aa3bb7a51a6ec1270bc947a8": [],
+        "813d981e1e78daffde4b2a05df35d054fcb4343f": [],
+        "ecf2a89a997ad4a14339b6a2f544e44b422620a0": [],
+        "f6517a7e69c10c6057d6c990a9f3ea22a2b62398": [],
+        "a5770eb54f7d13717098b5c34cc2dd51d2772021": ["86c06ff8864bc0e2233980c741b689714000850d"],
+        "b84d0aaa4e64fb95b105d0d38f6295fec7a82110": [],
+        "b586c66baf4824d175d051b3f5b06588c9aa2bc8": [],
+    }
+    if commit.hexsha in special:
+        return [repo.commit(c) for c in special[commit.hexsha]]
+
+    if commit.committed_date < datetime.datetime(2021, 1, 1).timestamp():
+        return []
+
+    regexp = re.compile(r'^([0-9a-f][0-9a-f]+)[, \(]?')
+
+    fixed = []
+    for line in commit.message.splitlines():
+        for tag, offset in (("Fixes", 1), ("MFC-with", 1), ("MFC with", 2)):
+            if line.startswith(tag + ':'):
+                line = ' '.join(line.split(':')[1:]).strip()
+                m = regexp.match(line)
+                if not m:
+                    continue
+                try:
+                    fixed.append(repo.commit(m.group(1)))
+                except (git.exc.BadName, ValueError):
+                    if warn:
+                        print(f"warning: {commit.hexsha[:12]}: {tag} tag "
+                              f"references unknown commit {m.group(1)}",
+                              file=sys.stderr)
+    return fixed
+
+
+def reverts(commit):
+    """
+    Look at the commit's log message and return the hash of the commit it
+    reverts, or None.
+    """
+    for line in commit.message.splitlines():
+        m = re.match(r'^This reverts commit ([0-9a-f]{40})\.', line)
+        if m:
+            return m.group(1)
+    return None
+
+
+def mfcclosure(repo, upstream, commits, _reverted=None):
+    """
+    Given a set of commits to MFC from the upstream branch, return a tuple
+    (tomfc, reverted) where tomfc is a list of all commits in the original
+    set plus those which fix up commits in the original set (excluding
+    reverted fixups), and reverted is the set of commit hashes that have
+    been reverted on the upstream branch.
+
+    Reverts are collected during the upstream walk, so no separate scan is
+    needed.  Recursive calls share the same reverted set via _reverted.
+    """
+    tomfc = []
+    for rev in commits:
+        try:
+            if ".." in rev:
+                revlist = list(repo.iter_commits(rev))
+                revlist.reverse()
+                tomfc.extend(revlist)
+            else:
+                tomfc.append(repo.commit(rev))
+        except git.exc.BadName:
+            err(1, f"Revision '{rev}' is invalid")
+
+    toplevel = _reverted is None
+    if toplevel:
+        _reverted = set()
+
+    tovisit = tomfc.copy()
+
+    for commit in repo.iter_commits(upstream):
+        r = reverts(commit)
+        if r:
+            _reverted.add(r)
+
+        if commit in tovisit:
+            tovisit.remove(commit)
+            if len(tovisit) == 0:
+                break
+            continue
+
+        for fix in fixes(repo, commit):
+            if fix in tomfc and commit not in tomfc:
+                if commit.hexsha in _reverted:
+                    print(f"warning: skipping {commit_summary(commit)}: "
+                          f"fixup was reverted upstream", file=sys.stderr)
+                    continue
+                i = tomfc.index(fix) + 1
+                sub, _ = mfcclosure(repo, upstream, [commit.hexsha],
+                                    _reverted=_reverted)
+                tomfc[i:i] = sub
+    else:
+        err(1, "the following commits are not in the upstream branch: " +
+            ', '.join([c.hexsha for c in tovisit]))
+    return (tomfc, _reverted)
+
+
+def mfc_origins(repo, commit, warn=False):
+    """
+    Given a commit, return a list of upstream commits that it was
+    cherry-picked from.  This is usually a single commit, but may be
+    multiple if several upstream commits were squashed into one MFC.
+
+    Handle a bunch of special commits where the existing cherry-pick
+    metadata is incorrect.
+    """
+    special = {
+        # stable/15
+        "e224f2c1b98ba065942c83d322cdb8e3987d0c81": ["068fea0aa15bceb7b6b01687542b58ee81d1d887"],
+        "48578fbefa666abfcfe3a47269343febefae94f9": ["728ec0c094ce473ae17ebd1adb05f0959bf3a68e"],
+        "2bf7d850c53e55ffced055235de432055f0cb9e2": ["7e79bc8ce70693a892c443c42af5ec16a95ba466"],
+        "e554d44c3a7ffa8664e89f35aec80b917f69e6b3": ["561dc357c2f5892af3aa481a1020860b7ff473e0"],
+        # stable/14
+        "aab45924bdb10338654e25ab9ecec106b7eb368b": ["c57c02ebf7bcc9b02a0dc11711e8d8a6960ad34b"],
+        "11dde2c8b7156a7d2072589c22c2f3c0de6880d8": ["62af5b9dc6205289a0ace964d060fba64e71ef28"],
+        "19f7b2bbc4e4fec33b7e8d546dd05a79533ca8e4": ["d0cbb1930e82a53b07b1091402ff14cdfe7a4898"],
+        "d034ff89b84f8470eb5bbcbb65c64c762e07f0bd": ["ac2156c139f8f685b84a71a7f0f164d6cccc7656"],
+        "fce2a3509a65a374820dc889929f8e8f5dbd1707": ["a9722e5ae8519a9a28e950dbd8d489178e9bc27e"],
+        "5946b0c6cbc77e6c5f62f5f7e635c6036e14f4d0": [],
+        "06bb8e1dab004ccb283f7a20fe84aa1326baf6b7": [],
+        "e5fadc41b48045d8978993d6c4ac72c64542b470": ["e20971500194d2f7299e9d01ca3b20e9bc6b4009"],
+        # stable/13
+        "fb4bc4c325eca15247a2e21ded0a70f92ec15488": ["c57c02ebf7bcc9b02a0dc11711e8d8a6960ad34b"],
+        "213406054e46b50d5df6d28b01a0a3410132b322": ["62af5b9dc6205289a0ace964d060fba64e71ef28"],
+        "eb6edafe8f484a69ff074018e5b93e481787923e": ["d0cbb1930e82a53b07b1091402ff14cdfe7a4898"],
+        "ced9fa71eaf95a27d5672c3419d7d9ca6c189168": ["ac2156c139f8f685b84a71a7f0f164d6cccc7656"],
+        "65bab39e140f97cace92a2923e50c6b654b02e22": ["346483b1f10454c5617a25d5e136829f60fb1184"],
+        "972637dc06a04432dc58e240b8ef3e9f538b98bb": ["9209ea69bc03e7e9f678b2294da7a0317b5c9c5b"],
+        "93a95ebbf7c8eb85aeb53a9fde329348992333e7": ["6ccff5c0452c4bc2a4dd497e39a801ab8db8a021"],
+        "9d31ae318711825d3a6ffa544d197708905435cf": ["aef815e7873b006bd040ac1690425709635e32e7"],
+        "a75324d674f5df10f1407080a49cfe933dbb06ec": ["64ae2f785e0672286901c15045a24cbc533538d3"],
+        "0729ba2f49c956789701aecb70f4f555181fd3a7": ["91a8bed5a49eb2d1e4e096a4c68c108cebec8818"],
+        "bec0d2c9c8413707b0fff8e65fb96aa53f149be3": ["8d5c7813061dfa0b187500dfe3aeea7a28181c13"],
+    }
+    if commit.hexsha in special:
+        return [repo.commit(s) for s in special[commit.hexsha]]
+
+    origins = []
+    for line in commit.message.splitlines():
+        m = re.match(r'^\(cherry picked from commit ([0-9a-f]{40})', line)
+        if m:
+            try:
+                origins.append(repo.commit(m.group(1)))
+            except (git.exc.BadName, ValueError):
+                if warn:
+                    print(f"warning: {commit.hexsha[:12]}: cherry-picked from "
+                          f"unknown commit {m.group(1)}", file=sys.stderr)
+    return origins
+
+
+def dangling(repo, upstream, author=None):
+    """
+    Find commits in the current branch which have been cherry-picked from
+    upstream but are missing fixup commits.
+    """
+    base = repo.merge_base('HEAD', upstream, all=True)[-1]
+    result = []
+    picked = []
+    mine = []
+    for commit in repo.iter_commits(base.hexsha + '..HEAD'):
+        refs = mfc_origins(repo, commit, warn=True)
+        for ref in refs:
+            picked.append(ref.hexsha)
+            if author is None or author in commit.author.email:
+                mine.append(ref.hexsha)
+    # Create a mapping of all upstream commits to their fixups,
+    # tracking reverts as we go.
+    fixups = {}
+    reverted = set()
+    for commit in repo.iter_commits(base.hexsha + '..' + upstream):
+        r = reverts(commit)
+        if r:
+            reverted.add(r)
+        for fix in fixes(repo, commit, warn=True):
+            if fix.hexsha not in fixups:
+                fixups[fix.hexsha] = []
+            fixups[fix.hexsha].append(commit.hexsha)
+    # For each of the user's cherry-picks, find fixups that haven't been
+    # cherry-picked (by anyone) or reverted.
+    for commit in mine:
+        for f in fixups.get(commit, []):
+            if f not in picked and f not in reverted:
+                result.append((repo.commit(f), repo.commit(commit)))
+    return result
+
+
+def mfc_after(commit):
+    """
+    Parse "MFC after:" tags from a commit message and return the time delta,
+    or None if there is no parseable MFC-after tag.
+    """
+    units = {
+        'day': 1, 'days': 1,
+        'week': 7, 'weeks': 7,
+        'month': 30, 'months': 30,
+    }
+    for line in commit.message.splitlines():
+        m = re.match(r'^MFC[ -]after:\s*(\d+)\s+(\w+)', line, re.IGNORECASE)
+        if m:
+            count = int(m.group(1))
+            unit = m.group(2).lower()
+            if unit in units:
+                return datetime.timedelta(days=count * units[unit])
+    return None
+
+
+def pending(repo, upstream, author=None, baking=False):
+    """
+    Find commits in the upstream branch that have an "MFC after:" tag, whose
+    waiting period has elapsed, and which have not been cherry-picked to the
+    current branch.
+
+    If baking is True, also include commits whose waiting period
+    has not yet elapsed.
+    """
+    base = repo.merge_base('HEAD', upstream, all=True)[-1]
+
+    # Collect the set of upstream commits already cherry-picked.
+    picked = set()
+    for commit in repo.iter_commits(base.hexsha + '..HEAD'):
+        for ref in mfc_origins(repo, commit):
+            picked.add(ref.hexsha)
+
+    results = {}
+
+    now = datetime.datetime.now(datetime.timezone.utc)
+    revlist = list(repo.iter_commits(base.hexsha + '..' + upstream))
+    revlist.reverse()
+    for commit in revlist:
+        r = reverts(commit)
+        if r and r in results:
+            # Don't report reverted commits.
+            del results[r]
+            continue
+
+        if commit.hexsha in picked:
+            # Don't report commits that have already been cherry-picked.
+            continue
+
+        delta = mfc_after(commit)
+        if delta is None:
+            # Not yet eligible for MFC.
+            continue
+
+        if author is not None and author not in commit.author.email:
+            # Don't report commits that don't match the requested author.
+            continue
+
+        committed = datetime.datetime.fromtimestamp(
+            commit.committed_date, tz=datetime.timezone.utc)
+        ready_date = committed + delta
+        ready = now >= ready_date
+
+        if not baking and not ready:
+            continue
+
+        results[commit.hexsha] = (commit, ready_date, ready)
+
+    return list(results.values())
+
+
+def cherry_pick(commit, edit=False):
+    """Cherry-pick a single commit with -x.  Abort on failure."""
+    cmd = ['git', 'cherry-pick', '-x']
+    if edit:
+        cmd.append('-e')
+    cmd.append(commit.hexsha)
+    result = subprocess.run(cmd, capture_output=False)
+    if result.returncode != 0:
+        print(f"\nCherry-pick of {commit.hexsha} ({commit.summary}) failed.",
+              file=sys.stderr)
+        print("Resolve the conflict and then re-run git mfc to continue,",
+              file=sys.stderr)
+        print("or run 'git cherry-pick --abort' to give up.", file=sys.stderr)
+        sys.exit(1)
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        prog='git mfc',
+        description='Cherry-pick commits from main to a stable branch, '
+                    'automatically including fixup commits.',
+    )
+    parser.add_argument(
+        '-e', '--edit', action='store_true',
+        help='Edit the commit message before committing',
+    )
+    parser.add_argument(
+        '-n', action='store_true',
+        help='List the commits that would be cherry-picked, but do not act',
+    )
+    parser.add_argument(
+        '-a', '--author', type=str, default=None,
+        help='Filter --pending/--dangling results by author (default: current user)',
+    )
+    parser.add_argument(
+        '--all', action='store_true',
+        help='With --pending/--dangling, show commits from all authors',
+    )
+    parser.add_argument(
+        '--baking', action='store_true',
+        help='With --pending, also show commits whose MFC-after period '
+             'has not yet elapsed',
+    )
+    parser.add_argument(
+        '--dangling', action='store_true',
+        help='Find cherry-picked commits in the current branch that are '
+             'missing fixup commits from the origin branch',
+    )
+    parser.add_argument(
+        '-f', '--force', action='store_true',
+        help='Cherry-pick commits even if they appear to be already present',
+    )
+    parser.add_argument(
+        '--ignore-reverts', action='store_true',
+        help='Cherry-pick commits even if they were reverted upstream',
+    )
+    parser.add_argument(
+        '--pending', action='store_true',
+        help='Show upstream commits with MFC-after tags that are ready to '
+             'be cherry-picked',
+    )
+    parser.add_argument(
+        '--origin', type=str, default=None,
+        help='Upstream branch (default: derived from sys/conf/newvers.sh)',
+    )
+    parser.add_argument(
+        '-r', '--remote', type=str, default=None,
+        help='Upstream remote (default: tracking remote of current branch)',
+    )
+    parser.add_argument(
+        'commits', nargs='*', metavar='revision',
+        help='Commits to MFC (hashes, ranges with "..", etc.)',
+    )
+    args = parser.parse_args()
+
+    if args.dangling and args.pending:
+        err(1, 'usage error: --dangling and --pending are mutually exclusive')
+    if (args.dangling or args.pending) and len(args.commits) > 0:
+        err(1, 'usage error: revisions cannot be specified with --dangling or --pending')
+    if not args.dangling and not args.pending and len(args.commits) == 0:
+        err(1, 'usage error: at least one revision is required')
+
+    origin = args.origin if args.origin else origin_branch()
+
+    repo = git.Repo()
+    if args.remote:
+        remote = args.remote
+    else:
+        try:
+            tracking = repo.active_branch.tracking_branch()
+            remote = tracking.remote_name if tracking else 'freebsd'
+        except (TypeError, ValueError):
+            remote = 'freebsd'
+
+    upstream = remote + '/' + origin
+
+    if not args.n:
+        repo.remotes[remote].fetch(origin)
+
+    show_all = getattr(args, 'all')
+    if show_all:
+        author = None
+    elif args.author:
+        author = args.author
+    elif args.dangling or args.pending:
+        author = repo.config_reader().get_value('user', 'email', default=None)
+        if author is None:
+            err(1, "could not determine user email; use -a or --all")
+    else:
+        author = None
+
+    if args.dangling:
+        missing = dangling(repo, upstream, author=author)
+        for fixup, commit in missing:
+            print(f'{commit_summary(fixup)} fixes {commit_summary(commit)}')
+    elif args.pending:
+        results = pending(repo, upstream, author=author,
+                          baking=args.baking)
+        for commit, ready_date, ready in results:
+            date_str = ready_date.strftime('%Y-%m-%d')
+            if ready:
+                status = f"ready since {date_str}"
+            else:
+                status = f"ready on {date_str}"
+            print(f'{commit_summary(commit)} ({status})')
+    else:
+        tomfc, reverted = mfcclosure(repo, upstream, args.commits)
+
+        # Check if any explicitly requested commits were reverted.
+        if not args.ignore_reverts:
+            for commit in tomfc:
+                if commit.hexsha in reverted:
+                    err(1, f"{commit_summary(commit)} was reverted "
+                        f"upstream; use --ignore-reverts to override")
+
+        # Find commits already cherry-picked to the current branch so we
+        # can skip them.  This lets the user re-run the same command after
+        # resolving a conflict without re-applying earlier commits.
+        if not args.force:
+            already_picked = set()
+            base = repo.merge_base('HEAD', upstream, all=True)[-1]
+            for c in repo.iter_commits(base.hexsha + '..HEAD'):
+                for ref in mfc_origins(repo, c):
+                    already_picked.add(ref.hexsha)
+        else:
+            already_picked = set()
+
+        if args.n:
+            for commit in tomfc:
+                if commit.hexsha in already_picked:
+                    continue
+                print(commit.hexsha, commit.summary)
+            return
+
+        for commit in tomfc:
+            if commit.hexsha in already_picked:
+                print(f"Skipping {commit.hexsha[:12]} {commit.summary} "
+                      f"(already cherry-picked)")
+                continue
+            print(f"Cherry-picking {commit.hexsha[:12]} {commit.summary}")
+            cherry_pick(commit, edit=args.edit)
+
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/tools/git/git-mfc.1 b/tools/tools/git/git-mfc.1
new file mode 100644
index 000000000000..acd27ef3cbcb
--- /dev/null
+++ b/tools/tools/git/git-mfc.1
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+.\"
+.\" Copyright (c) 2026 Mark Johnston <markj@FreeBSD.org>
+.\"
+.\" SPDX-License-Identifier: BSD-2-Clause
+.\"
+.Dd June 26, 2026
+.Dt GIT-MFC 1
+.Os
+.Sh NAME
+.Nm "git mfc"
+.Nd cherry-pick commits from an upstream branch to a stable or release branch
+.Sh SYNOPSIS
+.Nm
+.Op Fl efn
+.Op Fl -ignore-reverts
+.Op Fl -origin Ar branch
+.Op Fl r Ar remote
+.Ar revision ...
+.Nm
+.Fl -pending
+.Op Fl a Ar author
+.Op Fl -all
+.Op Fl -baking
+.Op Fl -origin Ar branch
+.Op Fl r Ar remote
+.Nm
+.Fl -dangling
+.Op Fl a Ar author
+.Op Fl -all
+.Op Fl -origin Ar branch
+.Op Fl r Ar remote
+.Sh DESCRIPTION
+The
+.Nm
+utility helps with MFCing (merge from CURRENT) commits to
+.Fx
+stable and release branches.
+It must be run from a checkout of the branch being MFCed
+.Em to .
+The origin branch is determined automatically and can be
+overridden with the
+.Fl -origin
+option.
+.Pp
+There are three modes of operation:
+.Bl -enum
+.It
+In the default mode, one or more revisions are specified on the command line.
+Each revision is cherry-picked with
+.Fl x
+to the current branch.
+The origin branch is scanned for commits with
+.Dq Fixes: ,
+.Dq MFC-with: ,
+or
+.Dq MFC with:
+tags referencing any of the specified revisions, and those fixup commits
+are automatically included in the correct order.
+.Pp
+If a specified revision has been reverted on the origin branch,
+.Nm
+refuses to cherry-pick it unless
+.Fl -ignore-reverts
+is given.
+Fixup commits that have been reverted are skipped with a warning.
+.Pp
+Commits that have already been cherry-picked to the current branch are
+automatically skipped.
+This allows the same
+.Nm
+command to be re-run after resolving a conflict without re-applying
+earlier commits.
+Use
+.Fl f
+to override this behavior.
+.It
+In
+.Fl -pending
+mode, no revisions are specified.
+Instead,
+.Nm
+scans the origin branch for commits with
+.Dq MFC after:
+tags whose waiting period has elapsed and which have not already been
+cherry-picked to the current branch.
+Commits that have been reverted upstream are excluded.
+By default, only commits authored by the current user
+.Pq as determined by Xr git-config 1
+are shown.
+.It
+In
+.Fl -dangling
+mode, no revisions are specified.
+Instead,
+.Nm
+finds commits in the current branch that have been cherry-picked from the
+origin branch but are missing associated fixup commits.
+Fixup commits that have been reverted upstream are excluded.
+By default, only cherry-picks authored by the current user
+.Pq as determined by Xr git-config 1
+are considered.
+.El
+.Pp
+The following options are available:
+.Bl -tag -width "-a author"
+.It Fl a Ar author , Fl -author Ar author
+With
+.Fl -pending
+or
+.Fl -dangling ,
+filter results to commits whose author email contains the given string.
+By default, the value of
+.Va user.email
+from
+.Xr git-config 1
+is used.
+.It Fl -all
+With
+.Fl -pending
+or
+.Fl -dangling ,
+show commits from all authors instead of only the current user.
+.It Fl -dangling
+Find cherry-picked commits in the current branch that are missing fixup
+commits from the origin branch.
+Cannot be combined with
+.Fl -pending
+or revision arguments.
+.It Fl e , Fl -edit
+Open the commit message in an editor before committing each cherry-pick.
+Passed through to
+.Xr git-cherry-pick 1 .
+.It Fl f , Fl -force
+Cherry-pick commits even if they appear to have already been cherry-picked
+to the current branch.
+By default,
+.Nm
+skips commits that are already present.
+.It Fl -ignore-reverts
+Cherry-pick commits even if they have been reverted on the origin branch.
+Without this flag,
+.Nm
+exits with an error when a reverted commit is specified.
+.It Fl -baking
+With
+.Fl -pending ,
+also show commits whose
+.Dq MFC after:
+waiting period has not yet elapsed.
+These are annotated with the date they become ready.
+.It Fl n
+Dry run.
+List the commits that would be cherry-picked, but do not actually
+cherry-pick them.
+The remote is not fetched in this mode.
+.It Fl -origin Ar branch
+Specify the upstream branch name.
+The default is determined automatically from
+.Pa sys/conf/newvers.sh :
+.Dq main
+for STABLE branches and
+.Dq stable/ Ns Ar major
+for RELEASE branches.
+.It Fl -pending
+Show upstream commits with
+.Dq MFC after:
+tags that are ready to be cherry-picked.
+Cannot be combined with
+.Fl -dangling
+or revision arguments.
+.It Fl r Ar remote , Fl -remote Ar remote
+Specify the git remote to fetch from.
+The default is the currently checked-out branch's upstream remote.
+.El
+.Pp
+Before running any operation,
+.Nm
+ensures that the origin is up to date by fetching it from the specified remote.
+.Sh IMPLEMENTATION NOTES
+.Nm
+is implemented in Python and depends on the gitpython module.
+.Pp
+.Nm
+uses text strings in commit log messages to establish relationships between
+commits.
+It recognizes the following tags in commit log messages:
+.Bl -tag -width "MFC after:"
+.It Dq Fixes: Ar hash
+Indicates that this commit fixes the commit identified by
+.Ar hash .
+When MFCing the referenced commit,
+.Nm
+will automatically include this fixup commit.
+.It Dq MFC-with: Ar hash , Dq MFC with: Ar hash
+Equivalent to
+.Dq Fixes: ;
+indicates that this commit should be MFCed together with the referenced commit.
+.It Dq MFC after: Ar N Ar unit
+Indicates that this commit should be MFCed after the specified waiting period.
+Recognized units are
+.Dq day ,
+.Dq days ,
+.Dq week ,
+.Dq weeks ,
+.Dq month ,
+and
+.Dq months .
+Used by the
+.Fl -pending
+mode.
+.El
+.Pp
+.Nm
+also looks for strings of the form,
+.Dq This reverts commit Ar hash ,
+inserted by
+.Xr git-revert 1 ,
+and
+.Dq cherry picked from commit Ar hash ,
+inserted by
+.Xr git-cherry-pick 1 .
+.Sh EXAMPLES
+Cherry-pick a single commit to the current branch, automatically including
+any fixup commits:
+.Bd -literal -offset indent
+$ git mfc abc123
+.Ed
+.Pp
+Cherry-pick a range of commits:
+.Bd -literal -offset indent
+$ git mfc abc123~..def456
+.Ed
+.Pp
+Preview which commits would be cherry-picked without actually doing it:
+.Bd -literal -offset indent
+$ git mfc -n abc123
+.Ed
+.Pp
+Cherry-pick a commit, opening an editor to amend the commit message first:
+.Bd -literal -offset indent
+$ git mfc -e abc123
+.Ed
+.Pp
+List your commits that are ready for MFC:
+.Bd -literal -offset indent
+$ git mfc --pending
+.Ed
+.Pp
+List pending commits from all authors:
+.Bd -literal -offset indent
+$ git mfc --pending --all
+.Ed
+.Pp
+Include commits whose MFC-after period has not yet elapsed:
+.Bd -literal -offset indent
+$ git mfc --pending --baking
+.Ed
+.Pp
+List commits ready for MFC by a specific author:
+.Bd -literal -offset indent
+$ git mfc --pending -a markj@FreeBSD.org
+.Ed
+.Pp
+Find MFCs in the current branch that are missing fixup commits:
+.Bd -literal -offset indent
+$ git mfc --dangling
+.Ed
+.Pp
+Cherry-pick a commit that was reverted upstream:
+.Bd -literal -offset indent
+$ git mfc --ignore-reverts abc123
+.Ed
+.Pp
+Use a different remote and origin branch:
+.Bd -literal -offset indent
+$ git mfc -r freebsd --origin main abc123
+.Ed
+.Sh SEE ALSO
+.Xr git-cherry-pick 1 ,
+.Xr git-config 1 ,
+.Xr git-revert 1 ,
+.Xr development 7
+.Sh AUTHORS
+The
+.Nm
+utility was written by
+.An -nosplit
+.An Mark Johnston Aq Mt markj@FreeBSD.org .