tsmretriever: On retrieve error, warn on partial files

Warn if we find files with size mismatch on retrieve errors.

There are some corner cases where this helps pinpoint the reason for
repeated retries etc. The most common case is duplicate files,
as described in #12

tsmretriever.pl

@@ -538,6 +538,19 @@ ()
 						printlog "dsmc output: " . join("\n", @out);
 					}
 
+					# Check if we got any files of
+					# unexpected size. This can happen if
+					# we run out of disk space, or if there
+					# are duplicate archived files with
+					# different file size.
+					while(my($f, $s) = each(%lfinfo)) {
+						my $fn = "$indir/$f";
+						my $fsize = (stat($fn))[7];
+						if(defined($fsize) && $fsize != $s) {
+							printlog("Warning: Retrieved file $fn size $fsize but it doesn't match request size $s. If the problem persists, manual investigation and intervention is needed.");
+						}
+					}
+
 					# sleep to pace ourselves if these are
 					# persistent reoccurring failures
 					sleep $conf{sleeptime};