narrow: validate spec files are well-formed during clone (BC) Previously, specfiles would get read then normalized. We want specfiles to be normalized on read so there is no confusion about what the format of specfiles should be. This commit validates the parsed result of --specfile. If entries aren't prefixed, an error is raised. Previously, validation would occur at exchange time, hence why we dropped a line of test output related to server iteraction. Differential Revision: https://phab.mercurial-scm.org/D4526