pacman-mirror add: offer to add files outside the current directory

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

pacman-mirror.sh

@@ -137,7 +137,8 @@ add () { # <file>
 	do
 		case "${path##*/}" in
 		mingw-w64-*.pkg.tar.xz)
-			arch=${path##mingw-w64-}
+			arch=${path##*/}
+			arch=${arch##mingw-w64-}
 			arch=${arch%%-*}
 			;;
 		*-*.pkg.tar.xz)