Update terminal renderer output depending on shell

Bash and zsh have different ways of escaping colors in the prompt, this
update checks the $SHELL environment variable and uses the correct
escape sequence for the current shell.

A known issue with this method is that $SHELL doesn't get updated when
switching shells (i.e. if you're running /bin/bash when you're in a zsh
shell) so in rare cases rendering errors may occur. A workaround which
is much slower is to parse the output of `ps -p $$` which always returns
the current shell.

powerline/ext/terminal/renderer.py

@@ -1,10 +1,23 @@
 # -*- coding: utf-8 -*-
 
+import os
+
 from powerline.renderer import Renderer
 
 
 class TerminalRenderer(Renderer):
 	'''Powerline terminal segment renderer.'''
+	_color_templates = {
+		'default': '[{code}m',
+		'bash': '\[[{code}m\]',
+		'zsh': '%{{[{code}m%}}',
+	}
+
+	def __init__(self, *args, **kwargs):
+		super(TerminalRenderer, self).__init__(*args, **kwargs)
+		shell = os.path.basename(os.environ.get('SHELL', 'default'))
+		self.color_template = self._color_templates[shell]
+
 	def hl(self, fg=None, bg=None, attr=None):
 		'''Highlight a segment.
 
@@ -29,4 +42,4 @@ class TerminalRenderer(Renderer):
 			else:
 				if attr & Renderer.ATTR_BOLD:
 					ansi += [1]
-		return '[{0}m'.format(';'.join(str(attr) for attr in ansi))
+		return self.color_template.format(code=';'.join(str(attr) for attr in ansi))