Auto merge of #1730 - RalfJung:zulip, r=oli-obk
Auto merge of #1730 - RalfJung:zulip, r=oli-obk

add date to Zulip notification subject

We sometimes have discussions in those threads; let's make sure we have a new thread for each new day (which likely means a new problem... or nobody got around to fixing things yet^^).

rust-lang/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri