git-svn: avoid respewing similar error messages for missing paths
We ignore errors if the path we're tracking did not exist for
a particular revision range, but we still print out warnings
telling the user about that.
As pointed out by Seth Falcon, this amounts to a lot of warnings
that could confuse and worry users. I'm not entirely comfortable
completely silencing the warnings, but showing one warning per
path that we track should be reasonable.
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>