Try some cursed Go templating, but it should work this time

.drone.yml

@@ -14,7 +14,7 @@ steps:
       use_sasl: yes
       sasl_password:
         from_secret: sasl_password
-      template: 'Updated https://casa.tildepages.org/ - {{ with build.message }}{{ if len . | gt 80 }}{{ slice . 0 80 | printf "%#v" }}{{ else }}{{ printf "%#v" . }}{{ end }}{{ end }} by {{ build.author }} - https://tildegit.org/casa/pages/commit/{{ build.commit }}'
+      template: 'Updated https://casa.tildepages.org/ - {{ $msg := build.message }}{{ if gt (len $msg) 80 }}{{ $msg = print (slice $msg 0 80) "…" }}{{ end }}{{ printf "%#v" $msg }} by {{ build.author }} - https://tildegit.org/casa/pages/commit/{{ build.commit }}'
     when:
       status:
         - success