Support running specific paster apps from .ini

Close #400

docs/source/run.rst

@@ -96,5 +96,9 @@ For example:
 
     gunicorn --paste development.ini -b :8080 --chdir /path/to/project
 
+Or use a different application:
+
+    gunicorn --paste development.ini#admin -b :8080 --chdir /path/to/project
+
 It is all here. No configuration files nor additional python modules to
 write !!

gunicorn/app/pasterapp.py

@@ -25,6 +25,7 @@ def paste_config(gconfig, config_url, relative_to, global_conf=None):
     sys.path.insert(0, relative_to)
     pkg_resources.working_set.add_entry(relative_to)
 
+    config_url = config_url.split('#')[0]
     cx = loadwsgi.loadcontext(SERVER, config_url, relative_to=relative_to,
             global_conf=global_conf)
     gc, lc = cx.global_conf.copy(), cx.local_conf.copy()

gunicorn/app/wsgiapp.py

@@ -14,14 +14,18 @@ from gunicorn import util
 class WSGIApplication(Application):
     def init(self, parser, opts, args):
         if opts.paste and opts.paste is not None:
+            app_name = 'main'
+            path = opts.paste
+            if '#' in path:
+                path, app_name = path.split('#')
             path = os.path.abspath(os.path.normpath(
-                os.path.join(util.getcwd(), opts.paste)))
+                os.path.join(util.getcwd(), path)))
 
             if not os.path.exists(path):
                 raise ConfigError("%r not found" % path)
 
             # paste application, load the config
-            self.cfgurl = 'config:%s' % path
+            self.cfgurl = 'config:%s#%s' % (path, app_name)
             self.relpath = os.path.dirname(path)
 
             from .pasterapp import paste_config

gunicorn/config.py

@@ -1222,7 +1222,12 @@ class Paste(Setting):
     validator = validate_string
     default = None
     desc = """\
-        Load a paste.deploy config file.
+        Load a paste.deploy config file. The argument may contain a "#" symbol
+        followed by the name of an app section from the config file, e.g.
+        "production.ini#admin".
+
+        At this time, using alternate server blocks is not supported. Use the
+        command line arguments to control server configuration instead.
         """