Add a tool to find MFC candidates

usage: mfc-candidates.sh [-ah] [-f from_branch] [-t to_branch]
    [-u user] [-X exclude_file] [path ...]

This tool compares git commit hashes that are in from_branch and not in
to_branch with hashes listed in "cherry picked from" lines, finding
commits that may be MFC candidates.  By default it searches for commits
by ${USER} but that can be overridden with -u for a specific user or -a
for all.

gonzo@'s MFC tracker is a web application that presents this sort of
information in a more convenient way, and unlike this script it tracks
"MFC After" status and timing.  However, it is sometimes useful to be
able to perform an offline search against a local repo.

Reviewed by:	jhb
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D34208

1 files changed, 163 insertions, 0 deletions

diff --git a/tools/tools/git/mfc-candidates.sh b/tools/tools/git/mfc-candidates.sh
new file mode 100644
index 000000000000..623edc7174a1
--- /dev/null
+++ b/tools/tools/git/mfc-candidates.sh
@@ -0,0 +1,163 @@
+#!/bin/sh
+
+#-
+# SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+#
+# Copyright 2022 The FreeBSD Foundation
+#
+# This software was developed by Ed Maste
+# under sponsorship from the FreeBSD Foundation.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted providing that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+from_branch=freebsd/main
+to_branch=freebsd/stable/13
+author="${USER}"
+
+# If pwd is a stable or release branch tree, default to it.
+cur_branch=$(git symbolic-ref --short HEAD 2>/dev/null)
+case $cur_branch in
+stable/*)
+	to_branch=$cur_branch
+	;;
+releng/*)
+	to_branch=$cur_branch
+	major=${cur_branch#releng/}
+	major=${major%.*}
+	from_branch=freebsd/stable/$major
+esac
+
+params()
+{
+	echo "from:             $from_branch"
+	echo "to:               $to_branch"
+	if [ -n "$author" ]; then
+		echo "author/committer: $author"
+	else
+		echo "author/committer: <all>"
+	fi
+}
+
+usage()
+{
+	echo "usage: $(basename $0) [-ah] [-f from_branch] [-t to_branch] [-u user] [-X exclude_file] [path ...]"
+	echo
+	params
+	exit 0
+}
+
+while getopts "af:ht:u:vX:" opt; do
+	case $opt in
+	a)
+		# All authors/committers
+		author=
+		;;
+	f)
+		from_branch=$OPTARG
+		;;
+	h)
+		usage
+		;;
+	t)
+		to_branch=$OPTARG
+		;;
+	u)
+		author=$OPTARG
+		;;
+	v)
+		verbose=1
+		;;
+	X)
+		if [ ! -r "$OPTARG" ]; then
+			echo "Exclude file $OPTARG not readable" >&2
+			exit 1
+		fi
+		exclude_file=$OPTARG
+		;;
+	esac
+done
+shift $(($OPTIND - 1))
+
+if [ $verbose ]; then
+	params
+	echo
+fi
+
+authorarg=
+if [ -n "$author" ]; then
+	# Match user ID in the email portion of author or committer
+	authorarg="--author <${author}@ --committer <${author}@"
+fi
+
+# Commits in from_branch after branch point
+commits_from()
+{
+	git rev-list --first-parent $authorarg $to_branch..$from_branch "$@" |\
+	    sort
+}
+
+# "cherry picked from" hashes from commits in to_branch after branch point
+commits_to()
+{
+	git log $from_branch..$to_branch --grep 'cherry picked from' "$@" |\
+	    sed -E -n 's/^[[:space:]]*\(cherry picked from commit ([0-9a-f]+)\)[[:space:]]*$/\1/p' |\
+	    sort
+}
+
+# Turn a list of short hashes (and optional descriptions) into a list of full
+# hashes.
+canonicalize_hashes()
+{
+	while read hash rest; do
+		if ! git show --pretty=%H --no-patch $hash; then
+			echo "error parsing hash list" >&2
+			exit 1
+		fi
+	done | sort
+}
+
+workdir=$(mktemp -d /tmp/find-mfc.XXXXXXXXXX)
+from_list=$workdir/commits-from
+to_list=$workdir/commits-to
+candidate_list=$workdir/candidates
+
+if [ -n "$exclude_file" ]; then
+	exclude_list=$workdir/commits-exclude
+	canonicalize_hashes < $exclude_file > $exclude_list
+fi
+
+commits_from "$@" > $from_list
+commits_to "$@" > $to_list
+
+comm -23 $from_list $to_list > $candidate_list
+
+if [ -n "$exclude_file" ]; then
+	mv $candidate_list $candidate_list.bak
+	comm -23 $candidate_list.bak $exclude_list > $candidate_list
+fi
+
+# Sort by (but do not print) commit time
+while read hash; do
+	git show --pretty='%ct %h %s' --no-patch $hash
+done < $candidate_list | sort -n | cut -d ' ' -f 2-
+
+rm -rf "$workdir"