pmrule: add FILE_EMPTY rule

Succeeds if the specified path is a file and is empty.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>

test/pacman/README

@@ -299,6 +299,7 @@ its DEPENDS field.
 	. FILE rules
 
   FILE_EXIST=path/to/file
+  FILE_EMPTY=path/to/file
   FILE_MODIFIED=path/to/file
   FILE_MODE=path/to/file|octal
   FILE_TYPE=path/to/file|type  (possible types: dir, file, link)

test/pacman/pmrule.py

@@ -112,6 +112,10 @@ def check(self, test):
             if case == "EXIST":
                 if not os.path.isfile(filename):
                     success = 0
+            elif case == "EMPTY":
+                if not (os.path.isfile(filename)
+                        and os.path.getsize(filename) == 0):
+                    success = 0
             elif case == "MODIFIED":
                 for f in test.files:
                     if f.name == key: