[xzize] Use default (not max) compression level

It's not recommended to always use -9 with xz.

compression_utils/README

@@ -36,7 +36,7 @@ explained in the main README file.
 # xzize.sh #
 
 The xzize script compresses an uncompressed file, or recompresses a
-compressed file to xz (with maximum compression level).
+compressed file to xz (with default compression level).
 
 Known compression formats are GZip (.gz), BZip2 (.bz2), LZMA (.lzma),
 and Lempel-Ziv (.Z). Short tar compressed suffixes are also allowed:

compression_utils/xzize.sh

@@ -20,9 +20,11 @@
 set -u
 
 # Destination file suffix when source file name suffix is a
-# 3-letter compressed tar suffix :
+# 3-letter compressed tar suffix:
 TAR_XZ_EXT=txz
 
+# Default compression level:
+COMPRESSION_LEVEL=
 
 test_extension()
 {
@@ -52,7 +54,7 @@ do_recompress()
 		return 0
 	fi
 	echo "Recompressing « $SOURCE » to  « $DEST »…"
-	$ACTION -c "$SOURCE" | xz -9 >"$DEST"
+	$ACTION -c "$SOURCE" | xz $COMPRESSION_LEVEL >"$DEST"
 	return $?
 }
 
@@ -157,6 +159,6 @@ for SOURCE in "$@" ; do
 
 	# Uncompressed file: fall back to simple compression
 	echo "Compressing « $SOURCE » to xz…"
-	xz -9 "$SOURCE"
+	xz $COMPRESSION_LEVEL "$SOURCE"
 
 done