[git_trace2] Add logs for critical cmds

Trace logs emitted from repo are not useful on error for many critical
commands. This change adds errors for critical commands to trace logs.

Change-Id: Ideb9358bee31e540bd84a94327a09ff9b0246a77
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/373814
Reviewed-by: Joanna Wang <jojwang@google.com>
Tested-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

subcmds/init.py

@@ -341,10 +341,12 @@ to update the working directory files.
                     quiet=opt.quiet,
                 )
             except wrapper.CloneFailure:
+                err_msg = "fatal: double check your --repo-rev setting."
                 print(
-                    "fatal: double check your --repo-rev setting.",
+                    err_msg,
                     file=sys.stderr,
                 )
+                self.git_event_log.ErrorEvent(err_msg)
                 sys.exit(1)
             branch = rp.GetBranch("default")
             branch.merge = remote_ref