Enable git trace2 event format logging.

Ways to enable logging:
1) Set git's trace2.eventtarget config variable to desired logging path
2) Specify path via --git_trace2_event_log option

A unique logfile name is generated per repo execution (based on the repo session-id).

Testing:
1) Verified git config 'trace2.eventtarget' and flag enable logging.
2) Verified version/start/end events are expected format:
  https://git-scm.com/docs/api-trace2#_event_format
3) Unit tests

Bug: https://crbug.com/gerrit/13706
Change-Id: I335eba68124055321c4149979bec36ac16ef81eb
Tested-by: Ian Kasprzak <iankaz@google.com>
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/292262
Reviewed-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Jonathan Nieder <jrn@google.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/main.py b/main.py
index e152de4f..a7c3c684 100755
--- a/main.py
+++ b/main.py
@@ -50,6 +50,7 @@ import event_log
 from repo_trace import SetTrace
 from git_command import user_agent
 from git_config import init_ssh, close_ssh, RepoConfig
+from git_trace2_event_log import EventLog
 from command import InteractiveCommand
 from command import MirrorSafeCommand
 from command import GitcAvailableCommand, GitcClientCommand
@@ -130,6 +131,8 @@ global_options.add_option('--version',
 global_options.add_option('--event-log',
                           dest='event_log', action='store',
                           help='filename of event log to append timeline to')
+global_options.add_option('--git-trace2-event-log', action='store',
+                          help='directory to write git trace2 event log to')
 
 
 class _Repo(object):
@@ -211,6 +214,7 @@ class _Repo(object):
             file=sys.stderr)
       return 1
 
+    git_trace2_event_log = EventLog()
     cmd.repodir = self.repodir
     cmd.client = RepoClient(cmd.repodir)
     cmd.manifest = cmd.client.manifest
@@ -261,6 +265,8 @@ class _Repo(object):
     start = time.time()
     cmd_event = cmd.event_log.Add(name, event_log.TASK_COMMAND, start)
     cmd.event_log.SetParent(cmd_event)
+    git_trace2_event_log.StartEvent()
+
     try:
       cmd.ValidateOptions(copts, cargs)
       result = cmd.Execute(copts, cargs)
@@ -303,10 +309,13 @@ class _Repo(object):
 
       cmd.event_log.FinishEvent(cmd_event, finish,
                                 result is None or result == 0)
+      git_trace2_event_log.ExitEvent(result)
+
       if gopts.event_log:
         cmd.event_log.Write(os.path.abspath(
                             os.path.expanduser(gopts.event_log)))
 
+      git_trace2_event_log.Write(gopts.git_trace2_event_log)
     return result