Before this change there was lots of duplicated code in all the
dircache using backends to support DirMove.
This change factors this code into the dircache library.
Dircache was changed to:
- Remove special cases for the root directory
- Remove Fatal errors
- Call FindRoot on behalf of the user wherever possible
- Bring up to modern Go standards
Backends were changed to:
- Remove calls to FindRoot
- Change calls to FindRootAndPath to FindPath
- Don't make special cases for the root
This fixes several corner cases, for example removing a non existent
directory if FindRoot hasn't been called.
- Change rclone/fs interfaces to accept context.Context
- Update interface implementations to use context.Context
- Change top level usage to propagate context to lover level functions
Context propagation is needed for stopping transfers and passing other
request-scoped values.
This bug was introduced by the v3 API conversion in 07f20dd1fd.
The problem was that dircache.FindPath doesn't work for the root directory.
This adds an internal error for dircache.FindPath being called with
the root directory. This makes a failing test, which the fix to the
drive backend fixes.
This also improves the DirCache integration test.
