1 files changed, 75 insertions, 0 deletions
diff --git a/morphlib/plugins/diff_plugin.py b/morphlib/plugins/diff_plugin.py
new file mode 100644
index 00000000..4763ba40
--- /dev/null
+++ b/morphlib/plugins/diff_plugin.py
@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+# Copyright © 2015  Codethink Limited
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+import cliapp
+
+from morphlib.cmdline_parse_utils import parse_cmdline_system_lists
+from morphlib.morphologyfinder import MorphologyFinder
+from morphlib.morphloader import MorphologyLoader
+from morphlib.util import new_repo_caches
+
+
+class DiffPlugin(cliapp.Plugin):
+
+    def enable(self):
+        self.app.add_subcommand(
+            'definition-diff', self.definition_diff,
+            arg_synopsis='REPO REF [SYSTEM]... - REPO REF [SYSTEM]...')
+
+    def disable(self):
+        pass
+
+    def definition_diff(self, args):
+        '''Show the difference between definitions.
+
+        When given two definition file specifiers, prints the logical
+        differences between the definitions.
+
+        '''
+        # NOTE: It would be more useful to have this operate at the graphed
+        #       dependency level, so you could use it to compare two different
+        #       systems, and avoid duplicated logic to interpret how
+        #       definitions are parsed.
+        #       However at the time of writing the data model does not support:
+        #       1.  Separately loading definition files from (repo, ref) and
+        #           having the loaded definitions being shared between computed
+        #           sources.
+        #       2.  Parsing definitions for multiple systems together.
+        #           This is because parameters from the parent definition (i.e.
+        #           arch) are passed down to included definitions, but this is
+        #           not taken into account for the lookup table, which is keyed
+        #           on name, so it can't handle two chunks with the same name
+        #           but different architectures.
+        from_spec, to_spec = parse_definition_lists(
+                                 definition_list_name_list=('from', 'to'),
+                                 args=args)
+
+        lrc, rrc = new_repo_caches(self.app)
+        ml = MorphologyLoader()
+
+
+        def load_morphset((reponame, ref, definitions)):
+            repo = lrc.get_updated_repo(reponame, ref=ref)
+            mf = MorphologyFinder(gitdir=repo.gitdir, ref=ref)
+            if not definitions:
+                definitions = mf.list_morphologies()
+            ms = MorphologySet()
+            for definition in definitions:
+                m = ml.parse_morphology_text(mf.read_morphology(definition),
+                                             definition)
+                ms.add_morphology(m)
+        from_morphset = load_morphset(from_spec)
+        to_morphset = load_morphset(to_spec)