complete cache conversion code

we need to create the borg cache directory

dry run was ignored, fixed.

process cache before segment, because we want to do the faster stuff first

borg/converter.py

@@ -17,7 +17,11 @@ class AtticRepositoryConverter(Repository):
         those are the files that need to be converted here, from most
         important to least important: segments, key files, and various
         caches, the latter being optional, as they will be rebuilt if
-        missing."""
+        missing.
+
+        we nevertheless do the order in reverse, as we prefer to do
+        the fast stuff first, to improve interactivity.
+        """
         print("reading segments from attic repository using borg")
         # we need to open it to load the configuration and other fields
         self.open(self.path, exclusive=False)
@@ -33,8 +37,8 @@ class AtticRepositoryConverter(Repository):
         self.lock = UpgradableLock(os.path.join(self.path, 'lock'),
                                    exclusive=True).acquire()
         try:
-            self.convert_segments(segments, dryrun)
             self.convert_cache(dryrun)
+            self.convert_segments(segments, dryrun)
         finally:
             self.lock.release()
             self.lock = None
@@ -146,13 +150,21 @@ class AtticRepositoryConverter(Repository):
         for cache in [ 'files', 'chunks' ]:
             attic_cache = os.path.join(attic_cache_dir, hexlify(self.id).decode('ascii'), cache)
             if os.path.exists(attic_cache):
-                borg_cache = os.path.join(get_cache_dir(), hexlify(self.id).decode('ascii'), cache)
-                shutil.copy(attic_cache, borg_cache)
+                borg_cache_dir = os.path.join(get_cache_dir(), hexlify(self.id).decode('ascii'))
+                if not os.path.exists(borg_cache_dir):
+                    os.makedirs(borg_cache_dir)
+                borg_cache = os.path.join(borg_cache_dir, cache)
+                print("copying attic cache from %s to %s" % (attic_cache, borg_cache))
+                if not dryrun:
+                    shutil.copy(attic_cache, borg_cache)
                 caches += [borg_cache]
+            else:
+                print("no %s cache found in %s" % (cache, attic_cache))
 
         for cache in caches:
             print("converting cache %s" % cache)
-            AtticRepositoryConverter.header_replace(cache, b'ATTICIDX', b'BORG_IDX')
+            if not dryrun:
+                AtticRepositoryConverter.header_replace(cache, b'ATTICIDX', b'BORG_IDX')
 
 
 class AtticKeyfileKey(KeyfileKey):