fbsd-r2g

#! /bin/sh
#
# fbsd-r2g
#
# This script converts a FreeBSD -r<nnn> SVN revision to
# a git commit ID, using the git repository stored in
# git://github.com/freebsd/freebsd.git
#
# Note: you must configure your copy of this repository
# with an additional `fetch =` line, e.g.:
#
#    fetch = +refs/notes/*:refs/notes/origin/*
#
# Currently, refs/notes/origin/commits is hardcoded into this
# script.

usage()
{
	echo "$0 revision [ ... ]"
}

warn()
{
	printf '%s\n' "$@" 1>&2
}

die()
{
	echo "fatal: $@" 1>&2
	exit 1
}

# We read all the notes from the topmost note's tree
# (as found by the git rev-parse below).  This tree
# contains files almost named "badf00dc0ffeedeadc0dedeadbeef..."
# whose contents are the notes for commit "badf00dc0ffee...".
# However, for performance reasons, git notes sub-tree the
# note, so that the actual file name is more like "ba/df/00/dc0ffee...".
#
# Normally, "git log" uses core.notesRef (which you would
# set to refs/notes/origin/commits) to look for a file whose
# name matches a commit, e.g., if it's about to show you commit
# badf00dc0ffee... it checks for this file in the tree pointed
# to by the ref in core.notesRef.  It knows to keep going if
# what it finds is a sub-tree, so if it sees a tree named "ba",
# it takes that off and looks for "df00dc0ffee...", and so on.
#
# We can do a similar job using "git grep", which can search
# a tree.  (Technically we could just point git grep at the commit
# and it would find the tree, but this makes sure the tree exists
# before we even try.)  We know that FreeBSD commits store a
# note of the form "svn path=...; revision=..." so we grep for
# the revision= part.
findrev()
{
	local rev path nraw nvalid status

	# remove leading "r" or "-r" if present; argument will
	# be svn-style r12345 or -r12345, and we just want the rev.
	rev="$1"
	case "$rev" in
	-r*) rev=${rev#-r};;
	r*) rev=${rev#r};;
	esac

	# This finds lines such as:
	#
	#     $TREE:$path/$to/$file:svn path=/head/; revision=352558
	#
	# The $TREE part is our $TREE argument, hence not useful.
	# We really just need the $path/to/file part -- e.g.,
	# 57/bb/1dff57ee60eac5aed02043a3903ccce141bc -- within
	# that tree.  Stripping out the slashes gives us the commit
	# hash ID for the right commit.
	git grep -e "revision=${rev}$" $TREE > $TF

	# We might not find any notes.  Even if we do, some
	# svn commits get a note, then wind up not in the local
	# repository.
	nraw=0
	nvalid=0
	while IFS=: read rev path matched; do
		path=$(echo $path | sed s,/,,g)
		nraw=$((nraw + 1))
		# Note: git rev-parse always believes a raw hash
		# is valid, so test with ^{commit}.
		if git rev-parse -q --verify $path^{commit} >/dev/null; then
			nvalid=$((nvalid + 1))
			status=""
		else
			status=" -- NOT IN REPO"
		fi
		echo "commit $path ($matched)$status"
	done < $TF
	# not sure which test to use here, let's use nvalid for now
	#test $nraw -gt 0
	test $nvalid -gt 0
}

TF=$(mktemp -t findrev) || die "cannot make temporary file"
trap "rm -f $TF; exit" 0 1 2 3 15

TREE=$(git rev-parse refs/notes/origin/commits^{tree} 2>/dev/null) ||
    die "no refs/notes/origin/commits tree - are you in a freebsd repo?"

case $# in
0) usage; exit 1;;
*) ;;
esac

status=0
for rev do
	findrev "$rev" || { warn "$rev: not found"; status=1; }
done
exit $status