Exclude ./nancy.db from FSEntry.from_path() scanning by default

src/nancy/fs.py

@@ -100,7 +100,7 @@ class FSEntry:
             self.sha256 = self.latest_version.sha256
 
     @classmethod
-    def from_path(cls, root, relpath='.', filestat=None):
+    def from_path(cls, root, relpath='.', filestat=None, exclude=['./nancy.db']):
         """
         Scan a path to instantiate (recursive).
         """
@@ -137,7 +137,8 @@ class FSEntry:
                     relpath=os.path.join(relpath, e.name),
                     filestat=e.stat(),
                 )
-                for e in direntries
+                for e in direntries \
+                    if os.path.join(relpath, e.name) not in exclude
             ]
             for c in children:  # now hash concatenated sorted hashes
                 # hash on perms+sha256 to enable recursively detecting perm