Fix binary diff

Dockerfile

@@ -0,0 +1,14 @@
+FROM python:3.8
+
+WORKDIR /usr/src/colcon-cache
+
+COPY requirements.txt .
+COPY test/requirements.txt ./test/
+RUN pip install -r test/requirements.txt
+
+COPY . .
+RUN colcon build \
+        --symlink-install
+
+RUN colcon test && \
+    colcon test-result --verbose

colcon_cache/task/lock/git.py

@@ -110,19 +110,21 @@ def compute_current_checksums(self, args, lockfile):  # noqa: D102
 
         lockfile.metadata['reference_revision'] = reference_commit.hexsha
 
-        diff_args = []
-        diff_args.append('--diff-filter={}'.format(args.git_diff_filter))
-        diff_args.append(reference_commit.hexsha)
-        diff_args.append(args.path)
-        diff = repo.git.diff(diff_args)
-
         h = hashlib.sha1()
         for _, checksum in lockfile.dependencies.items():
             h.update(bytes.fromhex(checksum))
 
         h.update(bytes.fromhex(reference_commit.hexsha))
         lockfile.checksums.reference = h.hexdigest()
 
+        diff = reference_commit.diff(None, paths=[args.path])
         if diff:
-            h.update(diff.encode('utf-8'))
+            for change_type in sorted(args.git_diff_filter):
+                for change in diff.iter_change_type(change_type):
+                    h.update(change.change_type.encode('utf-8'))
+                    h.update(change.a_path.encode('utf-8'))
+                    h.update(change.b_path.encode('utf-8'))
+                    if not change.deleted_file:
+                        hash_object = repo.git.hash_object(change.b_path)
+                        h.update(bytes.fromhex(hash_object))
         lockfile.checksums.current = h.hexdigest()

test/test_main.py

@@ -100,6 +100,10 @@ def test_main():
         with open(test_file, 'w') as f:
             f.write('def test_empty():\n    assert False\n')
 
+        test_file = \
+            ws_base / 'src' / 'test-repo' / 'test-package-c' / 'trash.txt'
+        os.remove(test_file)
+
         main(argv=argv + ['cache', 'lock'])
 
         main(argv=argv + ['list', '--packages-select-cache-modified'])