Merge branch 'pd/mergetool-nvimdiff'

Fix regression introduced when nvimdiff support in mergetool was added.

* pd/mergetool-nvimdiff:
  mergetool: avoid letting `list_tool_variants` break user-defined setups
  mergetools/bc: add `bc4` to the alias list for Beyond Compare

git-mergetool--lib.sh

@@ -138,6 +138,10 @@ setup_user_tool () {
 	merge_cmd () {
 		( eval $merge_tool_cmd )
 	}
+
+	list_tool_variants () {
+		echo "$tool"
+	}
 }
 
 setup_tool () {

mergetools/bc

@@ -25,4 +25,5 @@ translate_merge_tool_path() {
 list_tool_variants () {
 	echo bc
 	echo bc3
+	echo bc4
 }