Implement the new 'svnadmin load-revprops' sub-command. It takes a normal dumpfile but applies the revprop data only, and only to existing revisions.
We simply use the existing dumpfile parser infrastructure and implement two callbacks: Starting a revision record b/c we don't create a txn here and closing revisions - which sets the revprops. Revprop parser and magic header callbacks can be reused from the standard dumpfile loader.
* subversion/include/svn_repos.h (svn_repos_notify_action_t): Add a new notification for writing revprops. (svn_repos_load_fs_revprops): Declare new API. This is a variant of the existing svn_repos_load_fs5. We don't trigger hooks nor do we modify the UUID.
* subversion/libsvn_repos/load-fs-vtable.c (revprops_new_revision_record, revprops_close_revision): New callback implementations. (build_revprop_parser): New parser setup function. Based on the preexisting svn_repos_get_fs_build_parser5. (svn_repos_load_fs_revprops): Implement new API.
* subversion/svnadmin/svnadmin.c (svn_opt_subcommand_t): Declare new sub-command. (cmd_table): Add UI spec for the new sub-command. (repos_notify_handler): Handle the new notification type. (get_load_range): New utility, factored out from ... (subcommand_load): ... this. (subcommand_load_revprops): Implement the new sub-command. Code taken mostly from subcommand_load.