* Made secure() call doPrepare() for caller dummy proofing (especially those that don't check the status).
In FSFileBackend:
* Removed redundant wfMkdirParents() calls in FSFileBackend, we already have prepare() for this purpose. This also keeps it's behavior more consistent with the other backends.
* Made use of 'backend-fail-store' message in doStoreInternal().
Other:
* Updated unit tests and renamed $src => $source in some functions for consistency.
* Added some documentation comments and @since tags.
* Made 'success', 'successCount', and 'failCount' fields reflect the overall operation in FileBackendMultiWrite::doOperationsInternal(). This makes it match up with single-write backends.
* Made FileBackend::clearCache() part of the public API.
* Added getFileSize()/getFileStat() functions. Refactored some functions to use the stat function for better reuse and caching/consistency.
* Refactored streamFile() to allow for subclasses to avoid local file copying with less duplication. Also make last-modified check actually work since we always get the timestamp of the original file.
* Renamed 'ignoreErrors' parameter to 'force'.
In FileBackendMultiWrite:
* Simplified how read ops are done (use 'master' backend for consistency).
* Added consistency check to doOperationsInternal() to check if the files are synced.
* Various fixes after testing.
In StreamFile:
* Split out prepareForStream() function from stream() in StreamFile for code reuse.
In FileBackendTest:
* Properly cover FileBackendMultiWrite in tests.
* Various test improvements.
* Make sure FSFileIterator::current() directly returns the string path and that it is relative to the directory being searched.
* Fixed silly bug in testGetFileList that masked any bugs.
* Added a few code comments.
* Changed concatenate to store to a specified temp FS file rather than a final storage destination. This makes it better fit the use case (chunked upload), so we can avoid extra copying around. Subclasses no longer have to implement this function now as well.
* Added extensionFromPath() helper function.
* Moved createInternal() up a bit and fixed @see comments pointing to the wrong functions.
In FSFileBackend:
* Use parent implementation of doConcatenateInternal().
In FileRepo/File:
* Added FileRepo::ALLOW_STALE and made thumbnail transforms use it.
