diff -r e2a1648a6ce7 -r 29a7d591ff42 mercurial/commands.py
--- a/mercurial/commands.py	Tue May 03 15:26:51 2016 +0000
+++ b/mercurial/commands.py	Wed May 04 18:18:24 2016 +0100
@@ -4567,7 +4567,10 @@
     Returns 0 if successful.
     """
 
-    textwidth = min(ui.termwidth(), 80) - 2
+    textwidth = ui.configint('ui', 'textwidth', 78)
+    termwidth = ui.termwidth() - 2
+    if textwidth <= 0 or termwidth < textwidth:
+        textwidth = termwidth
 
     keep = opts.get('system') or []
     if len(keep) == 0: