mercurial/localrepo.py

--- a/mercurial/localrepo.py	Fri Apr 17 19:35:18 2020 +0900
+++ b/mercurial/localrepo.py	Mon Apr 20 14:37:10 2020 -0700
@@ -3016,6 +3016,12 @@
                     self.ui.write(
                         _(b'note: commit message saved in %s\n') % msgfn
                     )
+                    self.ui.write(
+                        _(
+                            b"note: use 'hg commit --logfile "
+                            b".hg/last-message.txt --edit' to reuse it\n"
+                        )
+                    )
                 raise
 
         def commithook(unused_success):