* subversion/tests/libsvn_subr/mergeinfo-test.c (verify_mergeinfo_parse): Rewrite conditional to avoid a GCC 5 warning "logical not is only applied to the left hand side of comparison". It also makes more sense to compare the svn_revnum_t directly to another integer.
Fix issue #4537 "mergeinfo parsing inconsistency: empty path". When parsing merginfo, allow the source path to be the empty string, for consistency.
This check was added in r868625. Since r1182771, all other non-canonical paths have been allowed and canonicalized by the parser for issue 4032 "Be graceful on non-canonical paths in mergeinfo".
* subversion/libsvn_subr/mergeinfo.c (parse_pathname): Don't throw an error if the mergeinfo path is empty.
* subversion/tests/libsvn_subr/mergeinfo-test.c (NBR_MERGEINFO_VALS, mergeinfo_vals, mergeinfo_paths, mergeinfo_ranges): Add an empty-path test case here. (NBR_BROKEN_MERGEINFO_VALS, broken_mergeinfo_vals): Remove the empty-path test case here.