Permit cache-url to work with fifos.

This makes it easier to work with temporary files - less traps
scattered around higher layer code.

Change-Id: I2fdd93115a7b0d289c2e28f8c133d4059de75b87

elements/cache-url/bin/cache-url

@@ -24,8 +24,14 @@ url=$1
 dest=$2
 time_cond=
 
+if [ -p $dest ]; then
+  type="fifo"
+  tmp=$(mktemp --tmpdir download.XXXXXXXX)
+else
+  type="normal"
   mkdir -p $(dirname $dest)
   tmp=$(mktemp $(dirname $dest)/.download.XXXXXXXX)
+fi
 
 if [ -f $dest -a -s $dest ] ; then
     time_cond="-z $dest"
@@ -44,8 +50,13 @@ if [ "$rcode" == "200" -o "${url:0:7}" == "file://" ] ; then
         rm -f $tmp
     else
         echo $success
+        if [ "fifo" = "$type" ]; then
+          cp $tmp $dest
+          rm $tmp
+        else
           mv $tmp $dest
         fi
+    fi
 # 213 is the response to a ftp MDTM command, curl outputs a 213 as the status
 # if the url redirected to a ftp server and Not-Modified
 elif [ "$rcode" = "304" -o "$rcode" = "213" ] ; then