commands: document the "event_log" class attribute

Add some notes explaining why it's instantiated at the Command class
level and not individual objects.

Change-Id: Ib8081bb8480e85f6d3dfc23953c6bbc6ecc64934
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/309323
Reviewed-by: Raman Tenneti <rtenneti@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/command.py b/command.py
index 8e930299..94f4d754 100644
--- a/command.py
+++ b/command.py
@@ -43,10 +43,15 @@ class Command(object):
   """Base class for any command line action in repo.
   """
 
-  event_log = EventLog()
   manifest = None
   _optparse = None
 
+  # Singleton for all commands to track overall repo command execution and
+  # provide event summary to callers.  Only used by sync subcommand currently.
+  #
+  # NB: This is being replaced by git trace2 events.  See git_trace2_event_log.
+  event_log = EventLog()
+
   # Whether this command is a "common" one, i.e. whether the user would commonly
   # use it or it's a more uncommon command.  This is used by the help command to
   # show short-vs-full summaries.