Fiber#transfer previously made it impossible to resume the fiber
if it was transferred to (no resuming the target of Fiber#transfer).
However, the documentation specifies that you cannot resume a fiber
that has transferred to another fiber (no resuming the source of
Fiber#transfer), unless control is transferred back.
Fix the code by setting the transferred flag on the current/source
fiber, and unsetting the transferred flag on the target fiber.
Added by jeremyevans (Jeremy Evans) over 4 years ago
Fix Fiber#transfer
Fiber#transfer previously made it impossible to resume the fiber
if it was transferred to (no resuming the target of Fiber#transfer).
However, the documentation specifies that you cannot resume a fiber
that has transferred to another fiber (no resuming the source of
Fiber#transfer), unless control is transferred back.
Fix the code by setting the transferred flag on the current/source
fiber, and unsetting the transferred flag on the target fiber.
Fixes [Bug #9664]
Fixes [Bug #12555]