Avoid rebuilds when unimportant morphology contents change

This changes the cache key generation so that it will ignore unimportant
fields of the morphology, e.g. description, build-depends, chunks.

description is unimportant because it does not affect building, and
build-depends/chunks are unimportant because they are already considered

1 files changed, 8 insertions, 0 deletions

diff --git a/morphlib/cachekeycomputer.py b/morphlib/cachekeycomputer.py
index a11334e3..a4ea10ed 100644
--- a/morphlib/cachekeycomputer.py
+++ b/morphlib/cachekeycomputer.py
@@ -91,6 +91,14 @@ class CacheKeyComputer(object):
         elif kind in ('system', 'stratum'):
             morphology = artifact.source.morphology
             le_dict = dict((k, morphology[k]) for k in morphology.keys())
+
+            # Disregard all fields of a morphology that aren't important
+            ignored_fields = ('strata', 'build-depends', 'description',
+                              'chunks')
+            for ignored_field in ignored_fields:
+                if ignored_field in le_dict:
+                    del le_dict[ignored_field]
+
             checksum = hashlib.sha1()
             self._hash_thing(checksum, le_dict)
             keys['morphology-sha1'] = checksum.hexdigest()