[PATCH 8 of 8] ui: unify argument name of ui.log()

[Yuya Nishihara]

# HG changeset patch
# User Yuya Nishihara <yuya at tcha.org>
# Date 1541926763 -32400
#      Sun Nov 11 17:59:23 2018 +0900
# Node ID 7d3ab070784c415798228718af187ad99928e7cb
# Parent  cae8cb38be59c8ec66f6be3fa9c2db432409497d
ui: unify argument name of ui.log()

It's called an "event" in both blackbox and logtoprocess.

diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -1709,10 +1709,10 @@ class ui(object):
         '''exists only so low-level modules won't need to import scmutil'''
         return scmutil.progress(self, topic, unit, total)
 
-    def log(self, service, *msg, **opts):
+    def log(self, event, *msg, **opts):
         '''hook for logging facility extensions
 
-        service should be a readily-identifiable subsystem, which will
+        event should be a readily-identifiable subsystem, which will
         allow filtering.
 
         *msg should be a newline-terminated format string to log, and