curses: use "text" interface if TERM=dumb

Differential Revision: https://phab.mercurial-scm.org/D3948

mercurial/ui.py

@@ -1214,7 +1214,7 b' class ui(object):'
                 "Feature %s does not handle all default interfaces" %
                 feature)
 
-        if self.plain():
+        if self.plain() or encoding.environ.get('TERM') == 'dumb':
             return "text"
 
         # Default interface for all the features

tests/test-commit-interactive-curses.t

@@ -368,6 +368,16 b" If only the default is set, we'll use th"
   $ chunkselectorinterface
   curses
 
+If TERM=dumb, we use text, even if the config says curses
+  $ chunkselectorinterface
+  curses
+  $ TERM=dumb chunkselectorinterface
+  text
+(Something is keeping TERM=dumb in the environment unless I do this, it's not
+scoped to just that previous command like in many shells)
+  $ TERM=xterm chunkselectorinterface
+  curses
+
 It is possible to override the default interface with a feature specific
 interface
   $ cp $HGRCPATH.pretest $HGRCPATH