Use "filepath" which is the current convention for naming full paths.
- Main use "name" which isn't obviously a file path.
- BlendFileData & FileGlobal used "filename" which is often
used for the name component of a path (without the directory).
The main goal of this refactor is to make BPath module use `IDTypeInfo`,
and move each ID-specific part of the `foreach_path` looper into their
own IDTypeInfo struct, using a new `foreach_path` callback.
Additionally, following improvements/cleanups are included:
* Attempt to get better, more consistent namings.
** In particular, move from `path_visitor` to more standard `foreach_path`.
* Update and extend documentation.
** API doc was moved to header, according to recent discussions on this
topic.
* Remove `BKE_bpath_relocate_visitor` from API, this is specific
callback that belongs in `lib_id.c` user code.
NOTE: This commit is expected to be 100% non-behavioral-change. This
implies that several potential further changes were only noted as
comments (like using a more generic solution for
`lib_id_library_local_paths`, addressing inconsistencies like path of
packed libraries always being skipped, regardless of the
`BKE_BPATH_FOREACH_PATH_SKIP_PACKED` `eBPathForeachFlag` flag value,
etc.).
NOTE: basic unittests were added to master already in
rBdcc500e5a265093bc9cc.
Reviewed By: brecht
Differential Revision: https://developer.blender.org/D13381
