+case "$onto_name" in
+*...*)
+ if left=${onto_name%...*} right=${onto_name#*...} &&
+ onto=$(git merge-base --all ${left:-HEAD} ${right:-HEAD})
+ then
+ case "$onto" in
+ ?*"$LF"?*)
+ die "$onto_name: there are more than one merge bases"
+ ;;
+ '')
+ die "$onto_name: there is no merge base"
+ ;;
+ esac
+ else
+ die "$onto_name: there is no merge base"
+ fi
+ ;;
+*)
+ onto=$(git rev-parse --verify "${onto_name}^0") || exit
+ ;;
+esac