mercurial/color.py

--- a/mercurial/color.py	Thu Dec 22 14:17:52 2016 +0100
+++ b/mercurial/color.py	Thu Dec 22 14:30:46 2016 +0100
@@ -9,7 +9,11 @@
 
 from .i18n import _
 
-from . import pycompat
+from . import (
+    encoding,
+    pycompat,
+    util
+)
 
 try:
     import curses
@@ -157,6 +161,71 @@
               "ECMA-48 color\n"))
         _terminfo_params.clear()
 
+def _modesetup(ui, coloropt):
+    if coloropt == 'debug':
+        return 'debug'
+
+    auto = (coloropt == 'auto')
+    always = not auto and util.parsebool(coloropt)
+    if not always and not auto:
+        return None
+
+    formatted = (always or (encoding.environ.get('TERM') != 'dumb'
+                 and ui.formatted()))
+
+    mode = ui.config('color', 'mode', 'auto')
+
+    # If pager is active, color.pagermode overrides color.mode.
+    if getattr(ui, 'pageractive', False):
+        mode = ui.config('color', 'pagermode', mode)
+
+    realmode = mode
+    if mode == 'auto':
+        if pycompat.osname == 'nt':
+            term = encoding.environ.get('TERM')
+            # TERM won't be defined in a vanilla cmd.exe environment.
+
+            # UNIX-like environments on Windows such as Cygwin and MSYS will
+            # set TERM. They appear to make a best effort attempt at setting it
+            # to something appropriate. However, not all environments with TERM
+            # defined support ANSI. Since "ansi" could result in terminal
+            # gibberish, we error on the side of selecting "win32". However, if
+            # w32effects is not defined, we almost certainly don't support
+            # "win32", so don't even try.
+            if (term and 'xterm' in term) or not w32effects:
+                realmode = 'ansi'
+            else:
+                realmode = 'win32'
+        else:
+            realmode = 'ansi'
+
+    def modewarn():
+        # only warn if color.mode was explicitly set and we're in
+        # a formatted terminal
+        if mode == realmode and ui.formatted():
+            ui.warn(_('warning: failed to set color mode to %s\n') % mode)
+
+    if realmode == 'win32':
+        _terminfo_params.clear()
+        if not w32effects:
+            modewarn()
+            return None
+        _effects.update(w32effects)
+    elif realmode == 'ansi':
+        _terminfo_params.clear()
+    elif realmode == 'terminfo':
+        _terminfosetup(ui, mode)
+        if not _terminfo_params:
+            ## FIXME Shouldn't we return None in this case too?
+            modewarn()
+            realmode = 'ansi'
+    else:
+        return None
+
+    if always or (auto and formatted):
+        return realmode
+    return None
+
 def configstyles(ui):
     for status, cfgeffects in ui.configitems('color'):
         if '.' not in status or status.startswith(('color.', 'terminfo.')):