Log repo.* config variables in git trace2 logger.

Bug: [google internal] b/181758736
Testing:
- Unit tests
- Verified repo git trace2 logs had expected data

Change-Id: I9af8a574377bd91115f085808c1271e9dee16a36
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/299182
Tested-by: Ian Kasprzak <iankaz@google.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Raman Tenneti <rtenneti@google.com>

git_trace2_event_log.py

@@ -132,6 +132,21 @@ class EventLog(object):
     exit_event['code'] = result
     self._log.append(exit_event)
 
+  def DefParamRepoEvents(self, config):
+    """Append a 'def_param' event for each repo.* config key to the current log.
+
+    Args:
+      config: Repo configuration dictionary
+    """
+    # Only output the repo.* config parameters.
+    repo_config = {k: v for k, v in config.items() if k.startswith('repo.')}
+
+    for param, value in repo_config.items():
+      def_param_event = self._CreateEventDict('def_param')
+      def_param_event['param'] = param
+      def_param_event['value'] = value
+      self._log.append(def_param_event)
+
   def _GetEventTargetPath(self):
     """Get the 'trace2.eventtarget' path from git configuration.