[#5108] Alloe extensions to define Click commands

Currently, there is no way for extension to add commands
to the main ckan one

This changes implements the possibility for extensions
to do it.

ckan/cli/cli.py

@@ -2,6 +2,7 @@
 
 import logging
 
+import ckan.plugins as p
 import click
 from ckan.cli import config_tool
 from ckan.cli import (
@@ -31,19 +32,33 @@
 log = logging.getLogger(__name__)
 
 
+class IClick(click.Group):
+    def get_command(self, ctx, name):
+        cmd = self.commands.get(name)
+        if not cmd:
+            ckan.invoke(ctx)
+            cmd = self.commands.get(name)
+        return cmd
+
+
 class CkanCommand(object):
 
     def __init__(self, conf=None):
         self.config = load_config(conf)
         self.app = make_app(self.config.global_conf, **self.config.local_conf)
 
 
-@click.group()
+@click.group(
+    invoke_without_command=True,
+    cls=IClick
+)
 @click.help_option(u'-h', u'--help')
 @click_config_option
 @click.pass_context
 def ckan(ctx, config, *args, **kwargs):
     ctx.obj = CkanCommand(config)
+    for plugin in p.PluginImplementations(p.ICLICommands):
+        ckan.add_command(plugin.get_commands())
 
 
 ckan.add_command(jobs.jobs)

ckan/plugins/interfaces.py

@@ -39,6 +39,7 @@
     u'IBlueprint',
     u'IPermissionLabels',
     u'IForkObserver',
+    u'ICLICommands',
 ]
 
 
@@ -1779,3 +1780,14 @@ def before_fork(self):
         u'''
         Called shortly before the CKAN process is forked.
         '''
+
+
+class ICLICommands(Interface):
+    u'''
+    Allow extensions to define click commands.
+    '''
+    def get_commands(self):
+        u'''
+        Return command function object
+        to be registered by the click.add_command.
+        '''