Enable regression labeling aliases

Author: apiraino

triagebot.toml

@@ -38,6 +38,14 @@ allow-unauthenticated = [
     "has-merge-commits",
 ]
 
+[relabel.to-stable]
+add-labels = ["regression-from-stable-to-stable"]
+rem-labels = ["regression-from-stable-to-beta", "regression-from-stable-to-nightly"]
+
+[relabel.to-beta]
+add-labels = ["regression-from-stable-to-beta"]
+rem-labels = ["regression-from-stable-to-stable", "regression-from-stable-to-nightly"]
+
 [review-submitted]
 # This label is added when a "request changes" review is submitted.
 reviewed_label = "S-waiting-on-author"
@@ -644,7 +652,7 @@ trigger_files = [
 zulip_stream = 245100 # #t-compiler/prioritization/alerts
 topic = "#{number} {title}"
 message_on_add = """\
-@*WG-prioritization/alerts* issue #{number} has been requested for prioritization.
+Issue #{number} has been requested for prioritization.
 
 # [Procedure](https://forge.rust-lang.org/compiler/prioritization.html)
 - Priority?
@@ -741,9 +749,9 @@ zulip_stream = 474880 # #t-compiler/backports
 topic = "#{number}: beta-backport nomination"
 message_on_add = [
     """\
-PR #{number} "{title}" fixes a regression.
-{recipients}, please evaluate nominating this PR for backport.
-The following poll is a vibe-check and not binding.
+PR #{number} "{title}" fixes a regression and has been nominated for backport.
+{recipients}, what do you think about it?
+This topic will help T-compiler getting context about it.
 """,
     """\
 /poll Should #{number} be beta backported?