WIP: Improve optimize sync conditions

This PR achieves the following:

- Do not disable optimize if we are switching from mirror to not mirror
  between two syncs. We can optmize in this case.
- Log additional reasons why we did not optimize in certain cases.
- Improve the readability of optimize conditions.

pulp_deb/app/tasks/synchronizing.py

@@ -546,19 +546,21 @@ def __init__(self, remote, optimize, mirror, previous_repo_version, *args, **kwa
         self.remote = remote
         self.optimize = optimize
         self.previous_repo_version = previous_repo_version
-        self.previous_sync_info = defaultdict(dict, previous_repo_version.info)
         self.sync_info = defaultdict()
         self.sync_info["remote_options"] = self._gen_remote_options()
         self.sync_info["sync_options"] = {
             "optimize": optimize,
             "mirror": mirror,
         }
         self.parsed_url = urlparse(remote.url)
-        self.sync_options_unchanged = (
-            self.previous_sync_info["remote_options"] == self.sync_info["remote_options"]
-            and self.previous_sync_info["sync_options"]["mirror"]
-            == self.sync_info["sync_options"]["mirror"]
-        )
+        if self.optimize:
+            previous_sync_info = defaultdict(dict, self.previous_repo_version.info)
+            if not previous_sync_info["remote_options"] == self.sync_info["remote_options"]:
+                log.info(_("Setting optimize=False since the remote options have changed."))
+                self.optimize = False
+            if mirror and not previous_sync_info["sync_options"]["mirror"]:
+                log.info(_("Setting optimize=False since this sync switches to mirror=True."))
+                self.optimize = False
 
     async def run(self):
         """
@@ -618,7 +620,7 @@ async def _handle_distribution(self, distribution):
         release_file = await self._create_unit(release_file_dc)
         if release_file is None:
             return
-        if self.optimize and self.sync_options_unchanged:
+        if self.optimize:
             previous_release_file = await _get_previous_release_file(
                 self.previous_repo_version, distribution
             )
@@ -899,7 +901,7 @@ async def _handle_package_index(
             else:
                 raise NoPackageIndexFile(relative_dir=package_index_dir)
 
-        if self.optimize and self.sync_options_unchanged:
+        if self.optimize:
             previous_package_index = await _get_previous_package_index(
                 self.previous_repo_version, relative_path
             )