Add stats about how many files we processed.

In the FILENAME MATCHING case it might be good to have the information,
which can also explain some of the timing spent. The example in
test/bossa.load currently loads data from 296 files total...

src/sources/common/md-methods.lisp

@@ -140,14 +140,18 @@
     (let* ((lp:*kernel* (make-kernel worker-count))
            (channel     (lp:make-channel))
            (path-list   (expand-spec (source copy))))
-      (loop :for path-spec :in path-list
-         :do (let ((table-source (clone-copy-for copy path-spec)))
-               (copy-from table-source
-                          :concurrency concurrency
-                          :kernel lp:*kernel*
-                          :channel channel
-                          :on-error-stop on-error-stop
-                          :disable-triggers disable-triggers)))
+      (with-stats-collection ("Files Processed" :section :post
+                                                :use-result-as-read t
+                                                :use-result-as-rows t)
+        (loop :for path-spec :in path-list
+           :count t
+           :do (let ((table-source (clone-copy-for copy path-spec)))
+                 (copy-from table-source
+                            :concurrency concurrency
+                            :kernel lp:*kernel*
+                            :channel channel
+                            :on-error-stop on-error-stop
+                            :disable-triggers disable-triggers))))
 
       ;; end kernel
       (with-stats-collection ("COPY Threads Completion" :section :post