diff_local.c

Reduce coupling between diff drivers and diff writers.

Let diff drivers anchor the diff-processor at the requested target paths,
rather than sometimes there and sometimes at the parent of one of them, in
summarize mode. The quirky anchoring still persists in non-summarize mode.

* subversion/libsvn_client/diff.c
(diff_driver_info_t): Expand comments.
(diff_wc_wc,
diff_repos_repos,
diff_repos_wc): Remove 'root_relpath' and 'root_is_dir' outputs; instead
anchor the diff processor at the requested targets if no 'ddi' coupling
parameter is given.
(do_diff,
svn_client_diff7,
svn_client_diff_peg7,
svn_client_diff_summarize2,
svn_client_diff_summarize_peg2): Update the calls accordingly.

* subversion/libsvn_client/diff_local.c,
subversion/libsvn_client/client.h
(svn_client__arbitrary_nodes_diff): Remove 'root_relpath' and 'root_is_dir'
outputs. Take an 'anchor_at_given_paths' mode flag and obey it.

* subversion/libsvn_client/diff_summarize.c,
subversion/libsvn_client/client.h
(summarize_baton_t,
send_summary): Remove path adjustment.
(svn_client__get_diff_summarize_callbacks): Remove path adjustment and
an unused parameter.

* subversion/libsvn_wc/diff_local.c,
subversion/include/private/svn_wc_private.h
(svn_wc__diff7): Remove 'root_relpath' and 'root_is_dir' outputs. Take an
'anchor_at_given_paths' mode flag and obey it.
(svn_wc_diff6): Update the call to svn_wc__diff7() accordingly.