dsv/dsv: record source URL in dsv-* file; new option -u to show it

This adds a second line to the dsv-* files, containing the source URL.
dsv -u <word> shows the URL.

Compatibility with older versions of dsv:

- "dsv -u" will fail with an error if running on an old data sheet
  database, while the rest of dsv works as before

- to update the database, run the usual "dsv setup ..."
  (most dsv-using projects have a "make dsv" target for this)

- older version of dsv will not be able to display data sheets or paths
  if run with an updated database

dsv/dsv

@@ -30,12 +30,13 @@ DSV_DIR=.dsv
 
 usage()
 {
-    echo "usage: $0 [-p] <component>" 2>&1
+    echo "usage: $0 [-p|-u] <component>" 2>&1
     echo "       $0 help" 2>&1
     echo "       $0 [ls]" 2>&1
     echo "       $0 setup <info-file> ..." 2>&1
     echo 2>&1
     echo "  -p   show the path instead of displaying the file " 2>&1
+    echo "  -u   show source URL instead of displaying the file " 2>&1
     exit 1
 }
 
@@ -78,7 +79,7 @@ flush()
     fi
     eval for n in $name $alias\; do \
         'nm=`echo "$n" | sed "s/%/%25/g;s|/|%2F|g"`;' \
-	echo '"$ds"' '>$DSV_DIR/dsv-$nm'\; \
+	\{ echo '"$ds"'\; echo '"$url"'\; \} '>$DSV_DIR/dsv-$nm'\; \
     done
     name=
     alias=
@@ -157,7 +158,18 @@ search()
 	if [ -d $DSV_DIR ]; then
     	    name=`echo "$1" | sed 's/%/%25/g;s|/|%2F|g'`
 	    if [ -r "$DSV_DIR/dsv-$name" ]; then
-		file=`cat "$DSV_DIR/dsv-$name"`
+		if $show_url; then
+		    url=`sed 1d "$DSV_DIR/dsv-$name"`
+		    if [ "$url" ]; then
+			echo "$url"
+			exit
+		    else
+			echo "$DSV_DIR/dsv-$name" \
+			  "does not contain an URL - please regenerate" 1>&2
+			exit 1
+		    fi
+		fi
+		file=`sed 1q "$DSV_DIR/dsv-$name"`
 		if [ ! -r "$DSV_DIR/$file" ]; then
 		    echo "$1 -> $file: does not exist" 2>&1
 		    exit 1
@@ -179,10 +191,15 @@ search()
 
 
 path=false
+show_url=false
 if [ "$1" = -p ]; then
     path=true
     shift
 fi
+if [ "$1" = -u ]; then
+    show_url=true
+    shift
+fi
 
 case "$1" in
     help|-*)	usage;;