factors out prune_out to bin

http/Makefile

@@ -3,34 +3,9 @@ all: microlog blog public out
 .PHONY: prune
 prune: prune_microlog prune_blog prune_out
 
-.SILENT: prune_out
 .PHONY: prune_out
 prune_out:
-	for out in $$(find out -type f); do \
-		out_basename="$$(basename "$$out")"; \
-		out_ext="$${out_basename##*\.}"; \
-		rel_path="$$(echo "$${out}" | cut -c5-)"; \
-		if [ -f "public/$${rel_path}" ]; then \
-			continue 2; \
-		fi; \
-		base_rel_path="$${rel_path%%.$${out_ext}}"; \
-		src_path="src/$${base_rel_path}.upp$${out_ext}"; \
-		if [ -f "$$src_path" ]; then \
-  		continue 2; \
-		fi; \
-		for layout in $$(find share/layouts -name "*.layout.upp$${out_ext}"); do \
-			layout="$$(basename "$$layout")"; \
-			layout="$${layout::$${#layout}-15}"; \
-			rel_path="$$(echo "$${out}" | cut -c5-)"; \
-			base_rel_path="$${rel_path%%.$${out_ext}}"; \
-			src_path="src/$${base_rel_path}.$${layout}.upp$${out_ext}"; \
-			if [ -f "$$src_path" ]; then \
-				continue 2; \
-			fi; \
-		done; \
-    echo "No source file found to match $${out}: removing it"; \
-		rm "$$out"; \
-	done
+	./bin/prune_out
 
 .SILENT: prune_microlog
 .PHONY: prune_microlog