convert: improve support for unusual .gitmodules Previously convert would throw an exception if it encountered a git commit with a .gitmodules file that was malformed (i.e. was missing, but had submodule files, or was malformed). Instead of breaking the convert entirely, let's print error messages and move on.

convert: handle .gitmodules with non-tab whitespaces The old implementation assumed .gitmodules file lines always began with tabs. It can be any whitespace, so lets trim the lines appropriately.