Add common global settings for images

The live_images, live_media and image_build phases have same options
that need to be specified on each image. This leads to a lot of
duplication in the config file. This patch adds global settings and
phase-level settings that allow to significantly reduce duplication.

Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

tests/test_phase_base.py

@@ -0,0 +1,73 @@
+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+import mock
+import unittest
+import os
+import sys
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from pungi.phases import base
+from tests.helpers import DummyCompose, PungiTestCase
+
+
+class Phase1(base.ImageConfigMixin, base.PhaseBase):
+    name = 'phase1'
+
+
+class Phase2(base.ImageConfigMixin, base.PhaseBase):
+    name = 'phase2'
+
+
+class Phase3(base.ImageConfigMixin, base.PhaseBase):
+    name = 'phase3'
+
+
+class DummyResolver(object):
+    def __init__(self):
+        self.num = 0
+
+    def __call__(self, url):
+        self.num += 1
+        return url.replace('HEAD', 'RES' + str(self.num))
+
+
+class ImageConfigMixinTestCase(PungiTestCase):
+
+    @mock.patch('pungi.util.resolve_git_url', new_callable=DummyResolver)
+    def test_git_url_resolved_once(self, resolve_git_url):
+        compose = DummyCompose(self.topdir, {
+            'global_ksurl': 'git://example.com/repo.git?#HEAD',
+            'phase1_ksurl': 'git://example.com/another.git?#HEAD',
+        })
+
+        p1 = Phase1(compose)
+        p2 = Phase2(compose)
+        p3 = Phase3(compose)
+
+        self.assertEqual(p1.get_ksurl({}),
+                         'git://example.com/another.git?#RES1')
+        # Phase-level setting retrieved second time.
+        self.assertEqual(p1.get_ksurl({}),
+                         'git://example.com/another.git?#RES1')
+
+        self.assertEqual(p2.get_ksurl({}),
+                         'git://example.com/repo.git?#RES2')
+        # Global setting retrieved again from same phase.
+        self.assertEqual(p2.get_ksurl({}),
+                         'git://example.com/repo.git?#RES2')
+
+        # Global setting retrieved from another phase.
+        self.assertEqual(p3.get_ksurl({}),
+                         'git://example.com/repo.git?#RES2')
+
+        # Local setting ignores global ones.
+        self.assertEqual(p3.get_ksurl({'ksurl': 'git://example.com/more.git?#HEAD'}),
+                         'git://example.com/more.git?#RES3')
+
+        self.assertEqual(resolve_git_url.num, 3, 'Resolver was not called three times')
+
+
+if __name__ == "__main__":
+    unittest.main()