merge(third_party/git): Merge squashed git subtree at v2.23.0

Merge commit '1b593e1ea4' as 'third_party/git'

third_party/git/mergetools/tortoisemerge

@@ -0,0 +1,32 @@
+can_diff () {
+	return 1
+}
+
+merge_cmd () {
+	if $base_present
+	then
+		basename="$(basename "$merge_tool_path" .exe)"
+		if test "$basename" = "tortoisegitmerge"
+		then
+			"$merge_tool_path" \
+				-base "$BASE" -mine "$LOCAL" \
+				-theirs "$REMOTE" -merged "$MERGED"
+		else
+			"$merge_tool_path" \
+				-base:"$BASE" -mine:"$LOCAL" \
+				-theirs:"$REMOTE" -merged:"$MERGED"
+		fi
+	else
+		echo "$merge_tool_path cannot be used without a base" 1>&2
+		return 1
+	fi
+}
+
+translate_merge_tool_path() {
+	if type tortoisegitmerge >/dev/null 2>/dev/null
+	then
+		echo tortoisegitmerge
+	else
+		echo tortoisemerge
+	fi
+}