wireproto: don't expose changegroupsubset capability if not available We just marked the changegroupsubset command as only available to version 1 of the wire transports. There is a capability of the same name of the command that indicates if the command is supported. This commit teaches the capabilities code to conditionally emit that capability depending on whether the command is available for the current transport. Most test output is reordering of capabilities. But the limited tests for version 2 of the SSH protocol do show the capability disappearing. Differential Revision: https://phab.mercurial-scm.org/D2486