Clarify some merge code.

* subversion/libsvn_client/merge.c
  (normalize_merge_sources_internal): Rewrite comments. Rename variables.
  (normalize_merge_sources): Rewrite the doc string. Fix a parameter
    declaration which was using the wrong typedef.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1435745 13f79535-47bb-0310-9956-ffa450edef68
Fix issues #3995 (redesign svn_fs_verify() for 1.8) and #4211 (verify
is slow and needs to handle node verification better).

This patch does two things. First, it adds a notification callback
to svn_fs_verify() and forwards its output to our console stream.

The second change is that revision-specific checks are begin moved
from svn_fs_fs__verify() to a new svn_fs_verify_rev() function.
Because the latter is being called as part of the per-revision checks,
progress is visible and access / cache locality is very much improved.

* subversion/include/svn_fs.h
  (svn_fs_progress_notify_func_t): declare new callback type
  (svn_fs_verify): add optional notification callbacks
  (svn_fs_verify_rev): declare new notification API

* subversion/include/svn_repos.h
  (svn_repos_notify_action_t): add svn_repos_notify_verify_struc_rev
   notification action

* subversion/libsvn_fs_base/fs.c
  (base_bdb_verify_rev): empty implementation of new API for BDB
  (fs_vtable,
   base_verify): update

* subversion/libsvn_fs_fs/fs.c
  (fs_vtable,
   fs_verify): update

* subversion/libsvn_fs_fs/fs_fs.h
  (svn_fs_fs__verify): update declaration
  (svn_fs_fs__verify_rev): declare implementation for new FS API

* subversion/libsvn_fs_fs/fs_fs.c
  (svn_fs_fs__verify): update and split off ...
  (svn_fs_fs__verify_rev): ... this part

* subversion/libsvn_fs/fs-loader.c
  (svn_fs_verify): update
  (svn_fs_verify_rev): new pass-through function

* subversion/libsvn_fs/fs-loader.h
  (fs_library_vtable_t,
   fs_vtable_t): update / extend vtables

* subversion/libsvn_fs_fs/rep-cache.h
  (svn_fs_fs__walk_rep_reference): add notification callbacks to API

* subversion/libsvn_fs_fs/rep-cache.c
  (svn_fs_fs__walk_rep_reference): send notifications

* subversion/libsvn_repos/dump.c
  (verify_fs2_notify_func_baton_t): new baton type for ...
  (verify_fs2_notify_func): ... this new forwarding notification handler
  (svn_repos_verify_fs2): initialize forwarding notification handle and
   use it to patch svn_fs_verify through to the parent; call the new
   per-revision verification API as well

* subversion/svnadmin/svnadmin.c
  (repos_notify_handler): handle svn_repos_notify_verify_struc_rev

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1435746 13f79535-47bb-0310-9956-ffa450edef68