Tor should reload keys from disk when receiving a SIGHUP
When running as a relay and receiving a HUP signal (reload) Tor should reload and validate keys from disk again. It would do the same validation operations related to ed25519 identity keys as when started normally.
This way, an operator can generate and move the new medium signing key and certificate to $datadirectory/keys and easily do a 'service tor reload'.
Change should be applied to ed25519_keygen branch. At this time, 0.2.7.2-alpha doesn't do the correct operations related to ed25519 identity keys at startup.
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