R1:6716d4f6ae17

Separate "shouldPublishRef()" from "isPermanentRef()" and set "IMPORTED_PERMANENT" more narrowly

Summary:
Ref T13591. Currently, the "IMPORTED_PERMANENT" flag (previously "IMPORTED_CLOSEABLE", until D21514) flag is set by using the result of "shouldPublishRef()".

This method returns the wrong value for the flag when there is a repository-level reason not to publish the ref (most commonly, because the repository is currently importing).

Although it's correct that commits should not be published in an…