comparators/deb: Fix matching for .deb archive members. (Closes: #903565)

my_members is iterated in DebContainer.perform_fuzzy_matching but is modified
in Container.comparisons.prep_yield which remove the current item from
my_members.

This causes an `RuntimeError: OrderedDict mutated during iteration` error.
This was not detected by the existing `test_deb.test_compare_different_compression`
test as it triggers only when there is more than one file in the .deb file.
(That test use only one file: control.tar.{gz,xz}).

Signed-off-by: Chris Lamb <lamby@debian.org>

diffoscope/comparators/deb.py

@@ -91,6 +91,11 @@ class DebContainer(LibarchiveContainer):
 
     def perform_fuzzy_matching(self, my_members, other_members):
         matched = set()
+
+        # Create local copies because they will be modified by consumer
+        my_members = dict(my_members)
+        other_members = dict(other_members)
+
         for name1 in my_members.keys():
             main, ext = os.path.splitext(name1)
             candidates = [name2 for name2 in other_members.keys() - matched

diffoscope/comparators/utils/fuzzy.py

@@ -34,7 +34,7 @@ def perform_fuzzy_matching(members1, members2):
     if tlsh is None or Config().fuzzy_threshold == 0:
         return
     already_compared = set()
-    # Perform local copies because they will be modified by consumer
+    # Create local copies because they will be modified by consumer
     members1 = dict(members1)
     members2 = dict(members2)
     for name1, (file1, _) in members1.items():

tests/comparators/test_deb.py

@@ -134,6 +134,9 @@ bug903391_deb1 = load_fixture('bug903391_1.deb')
 bug903391_deb2 = load_fixture('bug903391_2.deb')
 bug903401_deb1 = load_fixture('bug903401_1.deb')
 bug903401_deb2 = load_fixture('bug903401_2.deb')
+bug903565_deb1 = load_fixture('bug903565_1.deb')
+bug903565_deb2 = load_fixture('bug903565_2.deb')
+
 
 
 @skip_unless_tools_exist('xz')
@@ -151,3 +154,7 @@ def test_uncompressed_data_tar(bug903401_deb1, bug903401_deb2):
 
 def test_uncompressed_control_tar(bug903391_deb1, bug903391_deb2):
     bug903391_deb1.compare(bug903391_deb2)
+
+
+def test_compare_different_compression_multiple_files(bug903565_deb1, bug903565_deb2):
+    bug903565_deb1.compare(bug903565_deb2)