filter-repo: handle typechange modifications when first parent is pruned

Commit 509a624b (filter-repo: fix issue with pruning of empty commits,
2019-10-03) added code to get a new list of file changes when the first
parent was pruned.  However, this logic did not handle cases where one
of the file modifications was a typechange.  Add the necessary logic to
handle that case.

Signed-off-by: Elijah Newren <newren@gmail.com>

git-filter-repo

@@ -1595,7 +1595,7 @@ class GitUtils(object):
       oldmode, mode, oldhash, newhash, changetype = fileinfo.split()
       if changetype == b'D':
         file_changes.append(FileChange(b'D', path))
-      elif changetype in (b'A', b'M'):
+      elif changetype in (b'A', b'M', b'T'):
         identifier = HASH_TO_ID.get(newhash, newhash)
         file_changes.append(FileChange(b'M', path, identifier, mode))
       else: # pragma: no cover

t/t9390-filter-repo.sh

@@ -1408,6 +1408,43 @@ test_expect_success 'degenerate merge with non-matching filenames' '
 	)
 '
 
+test_expect_success 'degenerate merge with typechange' '
+	test_create_repo degenerate_merge_with_typechange &&
+	(
+		cd degenerate_merge_with_typechange &&
+
+		touch irrelevant_file &&
+		git add irrelevant_file &&
+		git commit -m "Irrelevant, unwanted file"
+		git branch A &&
+
+		git checkout --orphan B &&
+		git reset --hard &&
+		echo hello >world &&
+		git add world &&
+		git commit -m "greeting" &&
+		echo goodbye >planet &&
+		git add planet &&
+		git commit -m "farewell" &&
+
+		git checkout A &&
+		git merge --allow-unrelated-histories --no-commit B &&
+		rm world &&
+		ln -s planet world &&
+		git add world &&
+		git commit &&
+
+		git filter-repo --force --path world &&
+		test_path_is_missing irrelevant_file &&
+		test_path_is_missing planet &&
+		echo world >expect &&
+		git ls-files >actual &&
+		test_cmp expect actual &&
+
+		test_line_count = 2 <(git log --oneline HEAD)
+	)
+'
+
 test_expect_success 'Filtering a blob to make it match previous version' '
 	test_create_repo remove_unique_bits_of_blob &&
 	(