[compression_utils] Bug fixes on xzize

xzize:
- Fix bug with file names with spaces.
- Fix bug when invoking program without arguments.
- Handle error when input file is not a regular file instead of delegate
  to xz.
- Add an info message when compressing an uncompressed file.

lz:
- Info message on stdout instead of stderr when uncompressing.

compression_utils/lz

@@ -45,7 +45,7 @@ for F in "$@" ; do
 	if [ "$ACTION" = "t" ] ; then
 		echo "*** Listing « $F » ***" >&2
 	else
-		echo "Extracting « $F »…" >&2
+		echo "Extracting « $F »…"
 	fi
 
 	# Simple Tar archive

compression_utils/xzize

@@ -41,7 +41,7 @@ do_recompress()
 		return 0
 	fi
 	echo "Recompressing « $SOURCE » to  « $DEST »…"
-	$ACTION -c $SOURCE | xz -9 >$DEST
+	$ACTION -c "$SOURCE" | xz -9 >"$DEST"
 	return $?
 }
 
@@ -49,7 +49,7 @@ do_recompress()
 ## Verify number of arguments ##
 
 if [ $# -lt 1 ] ; then
-	echo "$PROGRAM requires at least one argument!" >&2
+	echo "$0 requires at least one argument!" >&2
 	exit 2
 fi
 
@@ -57,6 +57,11 @@ fi
 ## Process files ##
 
 for SOURCE in "$@" ; do
+	# Regular file?
+	if [ ! -f "$SOURCE" ] ; then
+		echo "Skipping source file « $SOURCE »: is not a regular file!" >&2
+		continue
+	fi
 
 	# GZip
 	test_extension "$SOURCE" gz
@@ -92,11 +97,12 @@ for SOURCE in "$@" ; do
 
 	# XZ
 	if test_extension "$SOURCE" xz ; then
-		echo "Skipping source file « $DEST »: it has already .xz suffix!" >&2
+		echo "Skipping source file « $DEST »: has already .xz suffix!" >&2
 		continue
 	fi
 
 	# Uncompressed file: fall back to simple compression
+	echo "Compressing « $SOURCE » to xz…"
 	xz -9 "$SOURCE"
 
 done