Ignore tempfiles created by Mercurial VCS

Mercurial creates temporary files in the .hg directory while running
certain commands. The creation of these should not invalidate the tree
status cache for the repository.

Fixes #2206

powerline/lib/vcs/mercurial.py

@@ -86,3 +86,8 @@ class Repository(object):
 			get_func=branch_name_from_config_file,
 			create_watcher=self.create_watcher,
 		)
+
+	@staticmethod
+	def ignore_event(path, name):
+		# Ignore temporary files created during mercurial commands
+		return path.endswith('.hg') and name.startswith(b'tmp')