color: be silent when falling back to ECMA-48 mode if "auto" mode was desired

Don't warn about missing setab/setaf terminfo entries unless we explicitly
asked for terminfo mode; fallback to ECMA-48 mode silently.

hgext/color.py

@@ -144,8 +144,11 b' def _terminfosetup(ui, mode):'
             ui.debug("no terminfo entry for %s\n" % e)
             del _terminfo_params[key]
     if not curses.tigetstr('setaf') or not curses.tigetstr('setab'):
-        ui.warn(_("no terminfo entry for setab/setaf: reverting to "
-          "ECMA-48 color\n"))
+        # Only warn about missing terminfo entries if we explicitly asked for
+        # terminfo mode.
+        if mode == "terminfo":
+            ui.warn(_("no terminfo entry for setab/setaf: reverting to "
+              "ECMA-48 color\n"))
         _terminfo_params = {}
 
 def _modesetup(ui, opts):