Rollup merge of rust-lang#116957 - fmease:meta-notify-rustdoc-zulip-on-backport-nominations, r=GuillaumeGomez

meta: notify #t-rustdoc Zulip stream on backport nominations

In July '23, it was decided to handle rustdoc-specific backport nominations in t-rustdoc meetings going forward ([Zulip announcement](https://rust-lang.zulipchat.com/#narrow/stream/266220-t-rustdoc/topic/T-rustdoc.20backports/near/374828518)). However, t-rustdoc meetings are far too infrequent for them to address nominations on time (contrary to the weekly t-compiler meetings).

Hence GuillaumeGomez and I came to the conclusion that {beta,stable}-nominated rustdoc PRs should be dealt with on a case by case basis, e.g. on Zulip.

This PR attempts to partially automate this process. ~~Sadly, `triagebot` is not quite as flexible has I've hoped. Blocked on `triagebot` improvements (see the `FIXME`s in this PR).~~ (Fixed in rust-lang/triagebot#1791).

r? GuillaumeGomez

Author: RalfJung

triagebot.toml

@@ -417,6 +417,54 @@ message_on_remove = "Issue #{number}'s prioritization request has been removed."
 message_on_close = "Issue #{number} has been closed while requested for prioritization."
 message_on_reopen = "Issue #{number} has been reopened."
 
+# FIXME: Patch triagebot to support `notify-zulip.<label>` getting mapped to an array of actions.
+#        At the moment, the beta-nominated+T-rustdoc action fully occupies the beta-nominated slot
+#        preventing others from adding more beta-nominated actions.
+[notify-zulip."beta-nominated"]
+required_labels = ["T-rustdoc"]
+zulip_stream = 266220 # #t-rustdoc
+topic = "beta-nominated: #{number}"
+# Zulip polls may not be preceded by any other text and pings & short links inside
+# the title of a poll don't get recognized. Therefore we need to send two messages.
+message_on_add = [
+    """\
+@*T-rustdoc* PR #{number} "{title}" has been nominated for beta backport.
+""",
+    """\
+/poll Approve beta backport of #{number}?
+approve
+decline
+don't know
+""",
+]
+message_on_remove = "PR #{number}'s beta-nomination has been removed."
+message_on_close = "PR #{number} has been closed. Thanks for participating!"
+message_on_reopen = "PR #{number} has been reopened. Pinging @*T-rustdoc*."
+
+# FIXME: Patch triagebot to support `notify-zulip.<label>` getting mapped to an array of actions.
+#        At the moment, the stable-nominated+T-rustdoc action fully occupies the stable-nominated slot
+#        preventing others from adding more stable-nominated actions.
+[notify-zulip."stable-nominated"]
+required_labels = ["T-rustdoc"]
+zulip_stream = 266220 # #t-rustdoc
+topic = "stable-nominated: #{number}"
+# Zulip polls may not be preceded by any other text and pings & short links inside
+# the title of a poll don't get recognized. Therefore we need to send two messages.
+message_on_add = [
+    """\
+@*T-rustdoc* PR #{number} "{title}" has been nominated for stable backport.
+""",
+    """\
+/poll Approve stable backport of #{number}?
+approve
+decline
+don't know
+""",
+]
+message_on_remove = "PR #{number}'s stable-nomination has been removed."
+message_on_close = "PR #{number} has been closed. Thanks for participating!"
+message_on_reopen = "PR #{number} has been reopened. Pinging @*T-rustdoc*."
+
 [notify-zulip."I-types-nominated"]
 zulip_stream = 326866 # #T-types/nominated
 topic = "#{number}: {title}"