0.12.3dev: Improved the help message for `trac-admin $ENV repository sync`.
0.12.3dev: Improved the help message for `trac-admin $ENV repository sync`.

Closes #9980.


git-svn-id: 764b04d0c6fbbea0ee05220aef3208173ff13049@10850 af82e41b-90c4-0310-8c96-b1721e28e2e2

rbaumg/trac,rbaumg/trac,rbaumg/trac,rbaumg/trac