git-svn: use SVN::Ra::get_dir2 when possible
This avoids the following failure with normal "get_dir" on newer
versions of SVN (tested with SVN 1.8.8-1ubuntu3.1):
Incorrect parameters given: Could not convert '%ld' into a number
get_dir2 also has the potential to be more efficient by requesting
less data.
ref: <
1414636504.45506.YahooMailBasic@web172304.mail.ir2.yahoo.com>
ref: <
1414722617.89476.YahooMailBasic@web172305.mail.ir2.yahoo.com>
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Cc: Hin-Tak Leung <htl10@users.sourceforge.net>