1 files changed, 574 insertions, 100 deletions

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 70cb2e30b..f96d887d2 100755
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -10,27 +10,83 @@
 # The original idea comes from Eric W. Biederman, in
 # http://article.gmane.org/gmane.comp.version-control.git/22407
 
-USAGE='(--continue | --abort | --skip | [--onto <branch>] <upstream> [<branch>])'
+OPTIONS_KEEPDASHDASH=
+OPTIONS_SPEC="\
+git-rebase [-i] [options] [--] <upstream> [<branch>]
+git-rebase [-i] (--continue | --abort | --skip)
+--
+ Available options are
+v,verbose          display a diffstat of what changed upstream
+onto=              rebase onto given branch instead of upstream
+p,preserve-merges  try to recreate merges instead of ignoring them
+s,strategy=        use the given merge strategy
+m,merge            always used (no-op)
+i,interactive      always used (no-op)
+ Actions:
+continue           continue rebasing process
+abort              abort rebasing process and restore original branch
+skip               skip current patch and continue rebasing process
+no-verify          override pre-rebase hook from stopping the operation
+root               rebase all reachable commmits up to the root(s)
+"
 
 . git-sh-setup
 require_work_tree
 
-DOTEST="$GIT_DIR/.dotest-merge"
-TODO="$DOTEST"/todo
+DOTEST="$GIT_DIR/rebase-merge"
+TODO="$DOTEST"/git-rebase-todo
 DONE="$DOTEST"/done
+MSG="$DOTEST"/message
+SQUASH_MSG="$DOTEST"/message-squash
+REWRITTEN="$DOTEST"/rewritten
+DROPPED="$DOTEST"/dropped
+PRESERVE_MERGES=
 STRATEGY=
+ONTO=
 VERBOSE=
+OK_TO_SKIP_PRE_REBASE=
+REBASE_ROOT=
+
+GIT_CHERRY_PICK_HELP="  After resolving the conflicts,
+mark the corrected paths with 'git add <paths>', and
+run 'git rebase --continue'"
+export GIT_CHERRY_PICK_HELP
 
 warn () {
 	echo "$*" >&2
 }
 
+output () {
+	case "$VERBOSE" in
+	'')
+		output=$("$@" 2>&1 )
+		status=$?
+		test $status != 0 && printf "%s\n" "$output"
+		return $status
+		;;
+	*)
+		"$@"
+		;;
+	esac
+}
+
+run_pre_rebase_hook () {
+	if test -z "$OK_TO_SKIP_PRE_REBASE" &&
+	   test -x "$GIT_DIR/hooks/pre-rebase"
+	then
+		"$GIT_DIR/hooks/pre-rebase" ${1+"$@"} || {
+			echo >&2 "The pre-rebase hook refused to rebase."
+			exit 1
+		}
+	fi
+}
+
 require_clean_work_tree () {
 	# test if working tree is dirty
 	git rev-parse --verify HEAD > /dev/null &&
-	git update-index --refresh &&
-	git diff-files --quiet &&
-	git diff-index --cached --quiet HEAD ||
+	git update-index --ignore-submodules --refresh &&
+	git diff-files --quiet --ignore-submodules &&
+	git diff-index --cached --quiet HEAD --ignore-submodules -- ||
 	die "Working tree is dirty"
 }
 
@@ -41,22 +97,47 @@ comment_for_reflog () {
 	''|rebase*)
 		GIT_REFLOG_ACTION="rebase -i ($1)"
 		export GIT_REFLOG_ACTION
+		;;
 	esac
 }
 
+last_count=
 mark_action_done () {
 	sed -e 1q < "$TODO" >> "$DONE"
 	sed -e 1d < "$TODO" >> "$TODO".new
 	mv -f "$TODO".new "$TODO"
+	count=$(grep -c '^[^#]' < "$DONE")
+	total=$(($count+$(grep -c '^[^#]' < "$TODO")))
+	if test "$last_count" != "$count"
+	then
+		last_count=$count
+		printf "Rebasing (%d/%d)\r" $count $total
+		test -z "$VERBOSE" || echo
+	fi
 }
 
 make_patch () {
-	parent_sha1=$(git rev-parse --verify "$1"^ 2> /dev/null)
-	git diff "$parent_sha1".."$1" > "$DOTEST"/patch
+	sha1_and_parents="$(git rev-list --parents -1 "$1")"
+	case "$sha1_and_parents" in
+	?*' '?*' '?*)
+		git diff --cc $sha1_and_parents
+		;;
+	?*' '?*)
+		git diff-tree -p "$1^!"
+		;;
+	*)
+		echo "Root commit"
+		;;
+	esac > "$DOTEST"/patch
+	test -f "$DOTEST"/message ||
+		git cat-file commit "$1" | sed "1,/^$/d" > "$DOTEST"/message
+	test -f "$DOTEST"/author-script ||
+		get_author_ident_from_commit "$1" > "$DOTEST"/author-script
 }
 
 die_with_patch () {
 	make_patch "$1"
+	git rerere
 	die "$2"
 }
 
@@ -65,89 +146,270 @@ die_abort () {
 	die "$1"
 }
 
+has_action () {
+	grep '^[^#]' "$1" >/dev/null
+}
+
 pick_one () {
-	case "$1" in -n) sha1=$2 ;; *) sha1=$1 ;; esac
-	git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
-	parent_sha1=$(git rev-parse --verify $sha1^ 2>/dev/null)
+	no_ff=
+	case "$1" in -n) sha1=$2; no_ff=t ;; *) sha1=$1 ;; esac
+	output git rev-parse --verify $sha1 || die "Invalid commit name: $sha1"
+	test -d "$REWRITTEN" &&
+		pick_one_preserving_merges "$@" && return
+	if test ! -z "$REBASE_ROOT"
+	then
+		output git cherry-pick "$@"
+		return
+	fi
+	parent_sha1=$(git rev-parse --verify $sha1^) ||
+		die "Could not get the parent of $sha1"
 	current_sha1=$(git rev-parse --verify HEAD)
-	if [ $current_sha1 = $parent_sha1 ]; then
-		git reset --hard $sha1
+	if test "$no_ff$current_sha1" = "$parent_sha1"; then
+		output git reset --hard $sha1
+		test "a$1" = a-n && output git reset --soft $current_sha1
 		sha1=$(git rev-parse --short $sha1)
-		warn Fast forward to $sha1
+		output warn Fast forward to $sha1
+	else
+		output git cherry-pick "$@"
+	fi
+}
+
+pick_one_preserving_merges () {
+	fast_forward=t
+	case "$1" in
+	-n)
+		fast_forward=f
+		sha1=$2
+		;;
+	*)
+		sha1=$1
+		;;
+	esac
+	sha1=$(git rev-parse $sha1)
+
+	if test -f "$DOTEST"/current-commit
+	then
+		if test "$fast_forward" = t
+		then
+			cat "$DOTEST"/current-commit | while read current_commit
+			do
+				git rev-parse HEAD > "$REWRITTEN"/$current_commit
+			done
+			rm "$DOTEST"/current-commit ||
+			die "Cannot write current commit's replacement sha1"
+		fi
+	fi
+
+	echo $sha1 >> "$DOTEST"/current-commit
+
+	# rewrite parents; if none were rewritten, we can fast-forward.
+	new_parents=
+	pend=" $(git rev-list --parents -1 $sha1 | cut -d' ' -s -f2-)"
+	if test "$pend" = " "
+	then
+		pend=" root"
+	fi
+	while [ "$pend" != "" ]
+	do
+		p=$(expr "$pend" : ' \([^ ]*\)')
+		pend="${pend# $p}"
+
+		if test -f "$REWRITTEN"/$p
+		then
+			new_p=$(cat "$REWRITTEN"/$p)
+
+			# If the todo reordered commits, and our parent is marked for
+			# rewriting, but hasn't been gotten to yet, assume the user meant to
+			# drop it on top of the current HEAD
+			if test -z "$new_p"
+			then
+				new_p=$(git rev-parse HEAD)
+			fi
+
+			test $p != $new_p && fast_forward=f
+			case "$new_parents" in
+			*$new_p*)
+				;; # do nothing; that parent is already there
+			*)
+				new_parents="$new_parents $new_p"
+				;;
+			esac
+		else
+			if test -f "$DROPPED"/$p
+			then
+				fast_forward=f
+				replacement="$(cat "$DROPPED"/$p)"
+				test -z "$replacement" && replacement=root
+				pend=" $replacement$pend"
+			else
+				new_parents="$new_parents $p"
+			fi
+		fi
+	done
+	case $fast_forward in
+	t)
+		output warn "Fast forward to $sha1"
+		output git reset --hard $sha1 ||
+			die "Cannot fast forward to $sha1"
+		;;
+	f)
+		first_parent=$(expr "$new_parents" : ' \([^ ]*\)')
+
+		if [ "$1" != "-n" ]
+		then
+			# detach HEAD to current parent
+			output git checkout $first_parent 2> /dev/null ||
+				die "Cannot move HEAD to $first_parent"
+		fi
+
+		case "$new_parents" in
+		' '*' '*)
+			test "a$1" = a-n && die "Refusing to squash a merge: $sha1"
+
+			# redo merge
+			author_script=$(get_author_ident_from_commit $sha1)
+			eval "$author_script"
+			msg="$(git cat-file commit $sha1 | sed -e '1,/^$/d')"
+			# No point in merging the first parent, that's HEAD
+			new_parents=${new_parents# $first_parent}
+			if ! GIT_AUTHOR_NAME="$GIT_AUTHOR_NAME" \
+				GIT_AUTHOR_EMAIL="$GIT_AUTHOR_EMAIL" \
+				GIT_AUTHOR_DATE="$GIT_AUTHOR_DATE" \
+				output git merge $STRATEGY -m "$msg" \
+					$new_parents
+			then
+				printf "%s\n" "$msg" > "$GIT_DIR"/MERGE_MSG
+				die_with_patch $sha1 "Error redoing merge $sha1"
+			fi
+			;;
+		*)
+			output git cherry-pick "$@" ||
+				die_with_patch $sha1 "Could not pick $sha1"
+			;;
+		esac
+		;;
+	esac
+}
+
+nth_string () {
+	case "$1" in
+	*1[0-9]|*[04-9]) echo "$1"th;;
+	*1) echo "$1"st;;
+	*2) echo "$1"nd;;
+	*3) echo "$1"rd;;
+	esac
+}
+
+make_squash_message () {
+	if test -f "$SQUASH_MSG"; then
+		COUNT=$(($(sed -n "s/^# This is [^0-9]*\([1-9][0-9]*\).*/\1/p" \
+			< "$SQUASH_MSG" | sed -ne '$p')+1))
+		echo "# This is a combination of $COUNT commits."
+		sed -e 1d -e '2,/^./{
+			/^$/d
+		}' <"$SQUASH_MSG"
 	else
-		git cherry-pick $STRATEGY "$@"
+		COUNT=2
+		echo "# This is a combination of two commits."
+		echo "# The first commit's message is:"
+		echo
+		git cat-file commit HEAD | sed -e '1,/^$/d'
 	fi
+	echo
+	echo "# This is the $(nth_string $COUNT) commit message:"
+	echo
+	git cat-file commit $1 | sed -e '1,/^$/d'
+}
+
+peek_next_command () {
+	sed -n "1s/ .*$//p" < "$TODO"
 }
 
 do_next () {
+	rm -f "$DOTEST"/message "$DOTEST"/author-script \
+		"$DOTEST"/amend || exit
 	read command sha1 rest < "$TODO"
 	case "$command" in
-	\#|'')
+	'#'*|''|noop)
 		mark_action_done
-		continue
 		;;
-	pick)
+	pick|p)
 		comment_for_reflog pick
 
 		mark_action_done
 		pick_one $sha1 ||
 			die_with_patch $sha1 "Could not apply $sha1... $rest"
 		;;
-	edit)
+	edit|e)
 		comment_for_reflog edit
 
 		mark_action_done
 		pick_one $sha1 ||
 			die_with_patch $sha1 "Could not apply $sha1... $rest"
 		make_patch $sha1
-		warn
+		git rev-parse --verify HEAD > "$DOTEST"/amend
+		warn "Stopped at $sha1... $rest"
 		warn "You can amend the commit now, with"
 		warn
 		warn "	git commit --amend"
 		warn
+		warn "Once you are satisfied with your changes, run"
+		warn
+		warn "	git rebase --continue"
+		warn
 		exit 0
 		;;
-	squash)
+	squash|s)
 		comment_for_reflog squash
 
-		test -z "$(grep -ve '^$' -e '^#' < $DONE)" &&
+		test -f "$DONE" && has_action "$DONE" ||
 			die "Cannot 'squash' without a previous commit"
 
 		mark_action_done
+		make_squash_message $sha1 > "$MSG"
 		failed=f
+		author_script=$(get_author_ident_from_commit HEAD)
+		output git reset --soft HEAD^
 		pick_one -n $sha1 || failed=t
-		MSG="$DOTEST"/message
-		echo "# This is a combination of two commits." > "$MSG"
-		echo "# The first commit's message is:" >> "$MSG"
-		echo >> "$MSG"
-		git cat-file commit HEAD | sed -e '1,/^$/d' >> "$MSG"
-		echo >> "$MSG"
-		echo "# And this is the 2nd commit message:" >> "$MSG"
-		echo >> "$MSG"
-		git cat-file commit $sha1 | sed -e '1,/^$/d' >> "$MSG"
-		git reset --soft HEAD^
-		author_script=$(get_author_ident_from_commit $sha1)
-		case $failed in
-		f)
+		case "$(peek_next_command)" in
+		squash|s)
+			USE_OUTPUT=output
+			MSG_OPT=-F
+			EDIT_OR_FILE="$MSG"
+			cp "$MSG" "$SQUASH_MSG"
+			;;
+		*)
+			USE_OUTPUT=
+			MSG_OPT=
+			EDIT_OR_FILE=-e
+			rm -f "$SQUASH_MSG" || exit
+			cp "$MSG" "$GIT_DIR"/SQUASH_MSG
+			rm -f "$GIT_DIR"/MERGE_MSG || exit
+			;;
+		esac
+		echo "$author_script" > "$DOTEST"/author-script
+		if test $failed = f
+		then
 			# This is like --amend, but with a different message
 			eval "$author_script"
-			export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE
-			git commit -F "$MSG" -e
-			;;
-		t)
+			GIT_AUTHOR_NAME="$GIT_AUTHOR_NAME" \
+			GIT_AUTHOR_EMAIL="$GIT_AUTHOR_EMAIL" \
+			GIT_AUTHOR_DATE="$GIT_AUTHOR_DATE" \
+			$USE_OUTPUT git commit --no-verify \
+				$MSG_OPT "$EDIT_OR_FILE" || failed=t
+		fi
+		if test $failed = t
+		then
 			cp "$MSG" "$GIT_DIR"/MERGE_MSG
 			warn
 			warn "Could not apply $sha1... $rest"
-			warn "After you fixed that, commit the result with"
-			warn
-			warn "  $(echo $author_script | tr '\012' ' ') \\"
-			warn "	  git commit -F \"$GIT_DIR\"/MERGE_MSG -e"
 			die_with_patch $sha1 ""
-		esac
+		fi
 		;;
 	*)
 		warn "Unknown command: $command $sha1 $rest"
 		die_with_patch $sha1 "Please fix this in the file $TODO."
+		;;
 	esac
 	test -s "$TODO" && return
 
@@ -156,10 +418,18 @@ do_next () {
 	OLDHEAD=$(cat "$DOTEST"/head) &&
 	SHORTONTO=$(git rev-parse --short $(cat "$DOTEST"/onto)) &&
 	NEWHEAD=$(git rev-parse HEAD) &&
-	message="$GIT_REFLOG_ACTION: $HEADNAME onto $SHORTONTO" &&
-	git update-ref -m "$message" $HEADNAME $NEWHEAD $OLDHEAD &&
-	git symbolic-ref HEAD $HEADNAME &&
+	case $HEADNAME in
+	refs/*)
+		message="$GIT_REFLOG_ACTION: $HEADNAME onto $SHORTONTO" &&
+		git update-ref -m "$message" $HEADNAME $NEWHEAD $OLDHEAD &&
+		git symbolic-ref HEAD $HEADNAME
+		;;
+	esac && {
+		test ! -f "$DOTEST"/verbose ||
+			git diff-tree --stat $(cat "$DOTEST"/head)..HEAD
+	} &&
 	rm -rf "$DOTEST" &&
+	git gc --auto &&
 	warn "Successfully rebased and updated $HEADNAME."
 
 	exit
@@ -170,46 +440,131 @@ do_rest () {
 	do
 		do_next
 	done
-	test -f "$DOTEST"/verbose &&
-		git diff --stat $(cat "$DOTEST"/head)..HEAD
-	exit
 }
 
-while case $# in 0) break ;; esac
+# skip picking commits whose parents are unchanged
+skip_unnecessary_picks () {
+	fd=3
+	while read command sha1 rest
+	do
+		# fd=3 means we skip the command
+		case "$fd,$command,$(git rev-parse --verify --quiet $sha1^)" in
+		3,pick,"$ONTO"*|3,p,"$ONTO"*)
+			# pick a commit whose parent is current $ONTO -> skip
+			ONTO=$sha1
+			;;
+		3,#*|3,,*)
+			# copy comments
+			;;
+		*)
+			fd=1
+			;;
+		esac
+		echo "$command${sha1:+ }$sha1${rest:+ }$rest" >&$fd
+	done <"$TODO" >"$TODO.new" 3>>"$DONE" &&
+	mv -f "$TODO".new "$TODO" ||
+	die "Could not skip unnecessary pick commands"
+}
+
+# check if no other options are set
+is_standalone () {
+	test $# -eq 2 -a "$2" = '--' &&
+	test -z "$ONTO" &&
+	test -z "$PRESERVE_MERGES" &&
+	test -z "$STRATEGY" &&
+	test -z "$VERBOSE"
+}
+
+get_saved_options () {
+	test -d "$REWRITTEN" && PRESERVE_MERGES=t
+	test -f "$DOTEST"/strategy && STRATEGY="$(cat "$DOTEST"/strategy)"
+	test -f "$DOTEST"/verbose && VERBOSE=t
+	test -f "$DOTEST"/rebase-root && REBASE_ROOT=t
+}
+
+while test $# != 0
 do
 	case "$1" in
+	--no-verify)
+		OK_TO_SKIP_PRE_REBASE=yes
+		;;
+	--verify)
+		;;
 	--continue)
+		is_standalone "$@" || usage
+		get_saved_options
 		comment_for_reflog continue
 
 		test -d "$DOTEST" || die "No interactive rebase running"
 
+		# Sanity check
+		git rev-parse --verify HEAD >/dev/null ||
+			die "Cannot read HEAD"
+		git update-index --ignore-submodules --refresh &&
+			git diff-files --quiet --ignore-submodules ||
+			die "Working tree is dirty"
+
+		# do we have anything to commit?
+		if git diff-index --cached --quiet --ignore-submodules HEAD --
+		then
+			: Nothing to commit -- skip this
+		else
+			. "$DOTEST"/author-script ||
+				die "Cannot find the author identity"
+			amend=
+			if test -f "$DOTEST"/amend
+			then
+				amend=$(git rev-parse --verify HEAD)
+				test "$amend" = $(cat "$DOTEST"/amend) ||
+				die "\
+You have uncommitted changes in your working tree. Please, commit them
+first and then run 'git rebase --continue' again."
+				git reset --soft HEAD^ ||
+				die "Cannot rewind the HEAD"
+			fi
+			export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE &&
+			git commit --no-verify -F "$DOTEST"/message -e || {
+				test -n "$amend" && git reset --soft $amend
+				die "Could not commit staged changes."
+			}
+		fi
+
 		require_clean_work_tree
 		do_rest
 		;;
 	--abort)
+		is_standalone "$@" || usage
+		get_saved_options
 		comment_for_reflog abort
 
+		git rerere clear
 		test -d "$DOTEST" || die "No interactive rebase running"
 
 		HEADNAME=$(cat "$DOTEST"/head-name)
 		HEAD=$(cat "$DOTEST"/head)
-		git symbolic-ref HEAD $HEADNAME &&
-		git reset --hard $HEAD &&
+		case $HEADNAME in
+		refs/*)
+			git symbolic-ref HEAD $HEADNAME
+			;;
+		esac &&
+		output git reset --hard $HEAD &&
 		rm -rf "$DOTEST"
 		exit
 		;;
 	--skip)
+		is_standalone "$@" || usage
+		get_saved_options
 		comment_for_reflog skip
 
+		git rerere clear
 		test -d "$DOTEST" || die "No interactive rebase running"
 
-		git reset --hard && do_rest
+		output git reset --hard && do_rest
 		;;
-	-s|--strategy)
-		shift
+	-s)
 		case "$#,$1" in
 		*,*=*)
-			STRATEGY="-s `expr "z$1" : 'z-[^=]*=\(.*\)'`" ;;
+			STRATEGY="-s "$(expr "z$1" : 'z-[^=]*=\(.*\)') ;;
 		1,*)
 			usage ;;
 		*)
@@ -217,90 +572,209 @@ do
 			shift ;;
 		esac
 		;;
-	--merge)
+	-m)
 		# we use merge anyway
 		;;
-	-C*)
-		die "Interactive rebase uses merge, so $1 does not make sense"
-		;;
-	-v|--verbose)
+	-v)
 		VERBOSE=t
 		;;
-	-i|--interactive)
+	-p)
+		PRESERVE_MERGES=t
+		;;
+	-i)
 		# yeah, we know
 		;;
-	''|-h)
-		usage
+	--root)
+		REBASE_ROOT=t
 		;;
-	*)
+	--onto)
+		shift
+		ONTO=$(git rev-parse --verify "$1") ||
+			die "Does not point to a valid commit: $1"
+		;;
+	--)
+		shift
+		test -z "$REBASE_ROOT" -a $# -ge 1 -a $# -le 2 ||
+		test ! -z "$REBASE_ROOT" -a $# -le 1 || usage
 		test -d "$DOTEST" &&
 			die "Interactive rebase already started"
 
 		git var GIT_COMMITTER_IDENT >/dev/null ||
 			die "You need to set your committer info first"
 
-		comment_for_reflog start
+		if test -z "$REBASE_ROOT"
+		then
+			UPSTREAM_ARG="$1"
+			UPSTREAM=$(git rev-parse --verify "$1") || die "Invalid base"
+			test -z "$ONTO" && ONTO=$UPSTREAM
+			shift
+		else
+			UPSTREAM=
+			UPSTREAM_ARG=--root
+			test -z "$ONTO" &&
+				die "You must specify --onto when using --root"
+		fi
+		run_pre_rebase_hook "$UPSTREAM_ARG" "$@"
 
-		ONTO=
-		case "$1" in
-		--onto)
-			ONTO=$(git rev-parse --verify "$2") ||
-				die "Does not point to a valid commit: $2"
-			shift; shift
-			;;
-		esac
+		comment_for_reflog start
 
 		require_clean_work_tree
 
-		if [ ! -z "$2"]
+		if test ! -z "$1"
 		then
-			git show-ref --verify --quiet "refs/heads/$2" ||
-				die "Invalid branchname: $2"
-			git checkout "$2" ||
-				die "Could not checkout $2"
+			output git show-ref --verify --quiet "refs/heads/$1" ||
+				die "Invalid branchname: $1"
+			output git checkout "$1" ||
+				die "Could not checkout $1"
 		fi
 
 		HEAD=$(git rev-parse --verify HEAD) || die "No HEAD?"
-		UPSTREAM=$(git rev-parse --verify "$1") || die "Invalid base"
-
-		test -z "$ONTO" && ONTO=$UPSTREAM
-
 		mkdir "$DOTEST" || die "Could not create temporary $DOTEST"
+
 		: > "$DOTEST"/interactive || die "Could not mark as interactive"
-		git symbolic-ref HEAD > "$DOTEST"/head-name ||
-			die "Could not get HEAD"
+		git symbolic-ref HEAD > "$DOTEST"/head-name 2> /dev/null ||
+			echo "detached HEAD" > "$DOTEST"/head-name
 
 		echo $HEAD > "$DOTEST"/head
-		echo $UPSTREAM > "$DOTEST"/upstream
+		case "$REBASE_ROOT" in
+		'')
+			rm -f "$DOTEST"/rebase-root ;;
+		*)
+			: >"$DOTEST"/rebase-root ;;
+		esac
 		echo $ONTO > "$DOTEST"/onto
+		test -z "$STRATEGY" || echo "$STRATEGY" > "$DOTEST"/strategy
 		test t = "$VERBOSE" && : > "$DOTEST"/verbose
+		if test t = "$PRESERVE_MERGES"
+		then
+			# $REWRITTEN contains files for each commit that is
+			# reachable by at least one merge base of $HEAD and
+			# $UPSTREAM. They are not necessarily rewritten, but
+			# their children might be.
+			# This ensures that commits on merged, but otherwise
+			# unrelated side branches are left alone. (Think "X"
+			# in the man page's example.)
+			if test -z "$REBASE_ROOT"
+			then
+				mkdir "$REWRITTEN" &&
+				for c in $(git merge-base --all $HEAD $UPSTREAM)
+				do
+					echo $ONTO > "$REWRITTEN"/$c ||
+						die "Could not init rewritten commits"
+				done
+			else
+				mkdir "$REWRITTEN" &&
+				echo $ONTO > "$REWRITTEN"/root ||
+					die "Could not init rewritten commits"
+			fi
+			# No cherry-pick because our first pass is to determine
+			# parents to rewrite and skipping dropped commits would
+			# prematurely end our probe
+			MERGES_OPTION=
+			first_after_upstream="$(git rev-list --reverse --first-parent $UPSTREAM..$HEAD | head -n 1)"
+		else
+			MERGES_OPTION="--no-merges --cherry-pick"
+		fi
 
-		SHORTUPSTREAM=$(git rev-parse --short $UPSTREAM)
 		SHORTHEAD=$(git rev-parse --short $HEAD)
 		SHORTONTO=$(git rev-parse --short $ONTO)
-		cat > "$TODO" << EOF
-# Rebasing $SHORTUPSTREAM..$SHORTHEAD onto $SHORTONTO
+		if test -z "$REBASE_ROOT"
+			# this is now equivalent to ! -z "$UPSTREAM"
+		then
+			SHORTUPSTREAM=$(git rev-parse --short $UPSTREAM)
+			REVISIONS=$UPSTREAM...$HEAD
+			SHORTREVISIONS=$SHORTUPSTREAM..$SHORTHEAD
+		else
+			REVISIONS=$ONTO...$HEAD
+			SHORTREVISIONS=$SHORTHEAD
+		fi
+		git rev-list $MERGES_OPTION --pretty=oneline --abbrev-commit \
+			--abbrev=7 --reverse --left-right --topo-order \
+			$REVISIONS | \
+			sed -n "s/^>//p" | while read shortsha1 rest
+		do
+			if test t != "$PRESERVE_MERGES"
+			then
+				echo "pick $shortsha1 $rest" >> "$TODO"
+			else
+				sha1=$(git rev-parse $shortsha1)
+				if test -z "$REBASE_ROOT"
+				then
+					preserve=t
+					for p in $(git rev-list --parents -1 $sha1 | cut -d' ' -s -f2-)
+					do
+						if test -f "$REWRITTEN"/$p -a \( $p != $UPSTREAM -o $sha1 = $first_after_upstream \)
+						then
+							preserve=f
+						fi
+					done
+				else
+					preserve=f
+				fi
+				if test f = "$preserve"
+				then
+					touch "$REWRITTEN"/$sha1
+					echo "pick $shortsha1 $rest" >> "$TODO"
+				fi
+			fi
+		done
+
+		# Watch for commits that been dropped by --cherry-pick
+		if test t = "$PRESERVE_MERGES"
+		then
+			mkdir "$DROPPED"
+			# Save all non-cherry-picked changes
+			git rev-list $REVISIONS --left-right --cherry-pick | \
+				sed -n "s/^>//p" > "$DOTEST"/not-cherry-picks
+			# Now all commits and note which ones are missing in
+			# not-cherry-picks and hence being dropped
+			git rev-list $REVISIONS |
+			while read rev
+			do
+				if test -f "$REWRITTEN"/$rev -a "$(grep "$rev" "$DOTEST"/not-cherry-picks)" = ""
+				then
+					# Use -f2 because if rev-list is telling us this commit is
+					# not worthwhile, we don't want to track its multiple heads,
+					# just the history of its first-parent for others that will
+					# be rebasing on top of it
+					git rev-list --parents -1 $rev | cut -d' ' -s -f2 > "$DROPPED"/$rev
+					short=$(git rev-list -1 --abbrev-commit --abbrev=7 $rev)
+					grep -v "^[a-z][a-z]* $short" <"$TODO" > "${TODO}2" ; mv "${TODO}2" "$TODO"
+					rm "$REWRITTEN"/$rev
+				fi
+			done
+		fi
+
+		test -s "$TODO" || echo noop >> "$TODO"
+		cat >> "$TODO" << EOF
+
+# Rebase $SHORTREVISIONS onto $SHORTONTO
 #
 # Commands:
-#  pick = use commit
-#  edit = use commit, but stop for amending
-#  squash = use commit, but meld into previous commit
+#  p, pick = use commit
+#  e, edit = use commit, but stop for amending
+#  s, squash = use commit, but meld into previous commit
+#
+# If you remove a line here THAT COMMIT WILL BE LOST.
+# However, if you remove everything, the rebase will be aborted.
+#
 EOF
-		git rev-list --no-merges --pretty=oneline --abbrev-commit \
-			--abbrev=7 --reverse $UPSTREAM..$HEAD | \
-			sed "s/^/pick /" >> "$TODO"
 
-		test -z "$(grep -ve '^$' -e '^#' < $TODO)" &&
+		has_action "$TODO" ||
 			die_abort "Nothing to do"
 
 		cp "$TODO" "$TODO".backup
-		${VISUAL:-${EDITOR:-vi}} "$TODO" ||
+		git_editor "$TODO" ||
 			die "Could not execute editor"
 
-		test -z "$(grep -ve '^$' -e '^#' < $TODO)" &&
+		has_action "$TODO" ||
 			die_abort "Nothing to do"
 
-		git checkout $ONTO && do_rest
+		test -d "$REWRITTEN" || skip_unnecessary_picks
+
+		git update-ref ORIG_HEAD $HEAD
+		output git checkout $ONTO && do_rest
+		;;
 	esac
 	shift
 done