updatemeta: correctly handle empty metadata When the repo metadata is empty (just created/cloned but not populated yet), there is no lastpulled file or the revmap doesn't have a last entry with hash. Currently "hg svn updatemeta" would crash due to unexpected exception. See issue reported at https://bitbucket.org/durin42/hgsubversion/issue/356/updatemeta-crashes-with-traceback-if-there The fix is to check the existence of lastpulled file and the hash entry in revmap, as part of "hg svn updatemeta" command. When they are not present, do a rebuildmetadata. Also added a new unit test, test_updatemeta.py.