Contributed by Steve Loughran.
This complements the StreamCapabilities Interface by allowing applications to probe for a specific path on a specific instance of a FileSystem client
to offer a specific capability.
This is intended to allow applications to determine
* Whether a method is implemented before calling it and dealing with UnsupportedOperationException.
* Whether a specific feature is believed to be available in the remote store.
As well as a common set of capabilities defined in CommonPathCapabilities,
file systems are free to add their own capabilities, prefixed with
fs. + schema + .
The plan is to identify and document more capabilities -and for file systems which add new features, for a declaration of the availability of the feature to always be available.
Note
* The remote store is not expected to be checked for the feature;
It is more a check of client API and the client's configuration/knowledge
of the state of the remote system.
* Permissions are not checked.
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