Do use sourcing when using <=tmux-1.8 by default

Otherwise each set option is displayed which under tmux-1.8 results in `[tmux]` 
in the statusline in place of `bash` (actually it is fine to check only whether 
tmux is 1.8 or not).

powerline/bindings/config.py

@@ -62,7 +62,7 @@ def get_tmux_configs(version):
 			yield (fname, priority + file_version.minor * 10 + file_version.major * 10000)
 
 
-def source_tmux_files(pl, args, source_tmux_file=source_tmux_file):
+def source_tmux_files(pl, args, tmux_version=None, source_tmux_file=source_tmux_file):
 	'''Source relevant version-specific tmux configuration files
 
 	Files are sourced in the following order:
@@ -70,9 +70,9 @@ def source_tmux_files(pl, args, source_tmux_file=source_tmux_file):
 	* If files for same versions are to be sourced then first _minus files are 
 	  sourced, then _plus files and then files without _minus or _plus suffixes.
 	'''
-	version = get_tmux_version(pl)
+	tmux_version = tmux_version or get_tmux_version(pl)
 	source_tmux_file(os.path.join(TMUX_CONFIG_DIRECTORY, 'powerline-base.conf'))
-	for fname, priority in sorted(get_tmux_configs(version), key=(lambda v: v[1])):
+	for fname, priority in sorted(get_tmux_configs(tmux_version), key=(lambda v: v[1])):
 		source_tmux_file(fname)
 	if not os.environ.get('POWERLINE_COMMAND'):
 		cmd = deduce_command()
@@ -172,29 +172,23 @@ def init_tmux_environment(pl, args, set_tmux_environment=set_tmux_environment):
 		' ' * powerline.renderer.strwidth(left_dividers['hard'])))
 
 
-def tmux_setup(pl, args):
-	init_tmux_environment(pl, args)
-	source_tmux_files(pl, args)
-
-
 TMUX_VAR_RE = re.compile('\$(_POWERLINE_\w+)')
 
 
-def tmux_setup_nosource(pl, args):
+def tmux_setup(pl, args):
 	tmux_environ = {}
+	tmux_version = get_tmux_version(pl)
 
-	def set_tmux_environment(varname, value, remove=True):
+	def set_tmux_environment_nosource(varname, value, remove=True):
 		tmux_environ[varname] = value
 
-	init_tmux_environment(pl, args, set_tmux_environment=set_tmux_environment)
-
 	def replace_cb(match):
 		return tmux_environ[match.group(1)]
 
 	def replace_env(s):
 		return TMUX_VAR_RE.subn(replace_cb, s)[0]
 
-	def source_tmux_file(fname):
+	def source_tmux_file_nosource(fname):
 		with open(fname) as fd:
 			for line in fd:
 				if line.startswith('#') or line == '\n':
@@ -203,7 +197,18 @@ def tmux_setup_nosource(pl, args):
 				args = [args[0]] + [replace_env(arg) for arg in args[1:]]
 				run_tmux_command(*args)
 
-	source_tmux_files(pl, args, source_tmux_file=source_tmux_file)
+	if args.source is None:
+		args.source = tmux_version < (1, 9)
+
+	if args.source:
+		ste = set_tmux_environment
+		stf = source_tmux_file
+	else:
+		ste = set_tmux_environment_nosource
+		stf = source_tmux_file_nosource
+
+	init_tmux_environment(pl, args, set_tmux_environment=ste)
+	source_tmux_files(pl, args, tmux_version=tmux_version, source_tmux_file=stf)
 
 
 def get_main_config(args):

powerline/bindings/tmux/powerline.conf

@@ -1,2 +1,2 @@
-if-shell 'env "$POWERLINE_CONFIG_COMMAND" tmux setup-nosource' '' 'run-shell "powerline-config tmux setup-nosource"'
+if-shell 'env "$POWERLINE_CONFIG_COMMAND" tmux setup' '' 'run-shell "powerline-config tmux setup"'
 # vim: ft=tmux

powerline/commands/config.py

@@ -22,7 +22,6 @@ TMUX_ACTIONS = {
 	'source': StrFunction(config.source_tmux_files, 'source'),
 	'setenv': StrFunction(config.init_tmux_environment, 'setenv'),
 	'setup': StrFunction(config.tmux_setup, 'setup'),
-	'setup-nosource': StrFunction(config.tmux_setup_nosource, 'setup-nosource'),
 }
 
 
@@ -61,7 +60,24 @@ def get_argparser(ArgumentParser=ConfigArgParser):
 		help='If action is `source\' then version-specific tmux configuration '
 		     'files are sourced, if it is `setenv\' then special '
 		     '(prefixed with `_POWERLINE\') tmux global environment variables '
-		     'are filled with data from powerline configuration.'
+		     'are filled with data from powerline configuration. '
+		     'Action `setup\' is just doing `setenv\' then `source\'.'
+	)
+	tpg = tmux_parser.add_mutually_exclusive_group()
+	tpg.add_argument(
+		'-s', '--source', action='store_true', default=None,
+		help='When using `setup\': always use configuration file sourcing. '
+		     'By default this is determined automatically based on tmux '
+		     'version: this is the default for tmux 1.8 and below.',
+	)
+	tpg.add_argument(
+		'-n', '--no-source', action='store_false', dest='source', default=None,
+		help='When using `setup\': in place of sourcing directly execute '
+		     'configuration files. That is, read each needed '
+		     'powerline-specific configuration file, substitute '
+		     '`$_POWERLINE_…\' variables with appropriate values and run '
+		     '`tmux config line\'. This is the default behaviour for '
+		     'tmux 1.9 and above.'
 	)
 
 	shell_parser = subparsers.add_parser('shell', help='Shell-specific commands')