diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -3208,7 +3208,12 @@
     repo.dirstate.write(tr)
     pending = tr and tr.writepending() and repo.root
 
-    editortext = repo.ui.edit(committext, ctx.user(), ctx.extra(),
+    # provide an unambigious path suffix so editors can provide special support
+    # for authoring Hg commit messages
+    extra = ctx.extra()
+    extra['suffix'] = '.hgcommit.txt'
+
+    editortext = repo.ui.edit(committext, ctx.user(), extra,
                               editform=editform, pending=pending,
                               repopath=repo.path)
     text = editortext