History.txt in sup-0.23 vs History.txt in sup-1.0

@@ -1,4 +1,9 @@
+== 1.0 / 2020-07-12
+
+No changes. The version number is incremented to 1.0 to reflect the fact that
+Sup is mature and no further backwards-incompatible changes are planned.
+
 == 0.23 / 2020-07-10
 
 * #505: Shell metacharacters in attachment filenames are no longer escaped when
   saving the attachment to disk using 's'. Fixes attachments being saved with
   unnecessary \ escapes in their filename. (Felix Van der Jeugt)