These are used as reference identities when checking the server certificate. These extra identities must result from user choices such as a selection of account type.
Will implement the changes to empathy in another bug.
Added tests in my extra-identities branch (rebased).
Changed param name 'extra-identities' to 'extra-certificate-identities'
Just some style points:
Why not initialize those variables to NULL when they're declared? Not a big thing though.
+ if (explicit_server != NULL && !tp_str_empty (explicit_server) &&
tp_str_empty checks for NULL so you don't have to.
Also I think this will conflict with the extra style patches you added to the bug 35410 branch.