wic: Add command to list available source plugins

Add a 'wic list source-plugins' command enabling users to get a list
of valid partition --sources.  This is useful not only for determining
sources to use in .wks partition statements, but also for making sense
of errors in .wks partition processing.

(From OE-Core rev: 37db9423e7872012fabde67e8858db5b512832f6)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/image/engine.py

@@ -174,6 +174,16 @@ def list_canned_image_help(scripts_path, fullpath):
             break
 
 
+def list_source_plugins():
+    """
+    List the available source plugins i.e. plugins available for --source.
+    """
+    plugins = pluginmgr.get_source_plugins()
+
+    for plugin in plugins:
+        print "  %s" % plugin
+
+
 def wic_create(args, wks_file, rootfs_dir, bootimg_dir, kernel_dir,
                native_sysroot, hdddir, staging_data_dir, scripts_path,
                image_output_dir, debug, properties_file, properties=None):
@@ -258,6 +268,9 @@ def wic_list(args, scripts_path, properties_file):
         if args[0] == "images":
             list_canned_images(scripts_path)
             return True
+        elif args[0] == "source-plugins":
+            list_source_plugins()
+            return True
         elif args[0] == "properties":
             return True
         else:

scripts/lib/mic/plugin.py

@@ -117,6 +117,22 @@ class PluginMgr(object):
 
         return pluginbase.get_plugins(ptype)
 
+    def get_source_plugins(self):
+        """
+        Return list of available source plugins.
+        """
+        plugins_dir = self._build_plugin_dir_list(self.plugin_dir, 'source')
+
+        self.append_dirs(plugins_dir)
+
+        plugins = []
+
+        for _source_name, klass in self.get_plugins('source').iteritems():
+            plugins.append(_source_name)
+
+        return plugins
+
+
     def get_source_plugin_methods(self, source_name, methods):
         """
         The methods param is a dict with the method names to find.  On