tree: enforce coverage of silent entry replacement

tests-clar/object/tree/duplicateentries.c

+#include "clar_libgit2.h"
+#include "tree.h"
+
+static git_repository *_repo;
+
+void test_object_tree_duplicateentries__initialize(void) {
+   _repo = cl_git_sandbox_init("testrepo");
+}
+
+void test_object_tree_duplicateentries__cleanup(void) {
+   cl_git_sandbox_cleanup();
+}
+
+/*
+ * $ git show --format=raw refs/heads/dir
+ * commit 144344043ba4d4a405da03de3844aa829ae8be0e
+ * tree d52a8fe84ceedf260afe4f0287bbfca04a117e83
+ * parent cf80f8de9f1185bf3a05f993f6121880dd0cfbc9
+ * author Ben Straub <bstraub@github.com> 1343755506 -0700
+ * committer Ben Straub <bstraub@github.com> 1343755506 -0700
+ * 
+ *     Change a file mode
+ * 
+ * diff --git a/a/b.txt b/a/b.txt
+ * old mode 100644
+ * new mode 100755
+ *
+ * $ git ls-tree d52a8fe84ceedf260afe4f0287bbfca04a117e83
+ * 100644 blob a8233120f6ad708f843d861ce2b7228ec4e3dec6    README
+ * 040000 tree 4e0883eeeeebc1fb1735161cea82f7cb5fab7e63    a
+ * 100644 blob 45b983be36b73c0788dc9cbcb76cbb80fc7bb057    branch_file.txt
+ * 100644 blob a71586c1dfe8a71c6cbf6c129f404c5642ff31bd    new.txt
+ */
+
+static void tree_checker(
+	git_oid *tid,
+	const char *expected_sha,
+	git_filemode_t expected_filemode)
+{
+	git_tree *tree;
+	const git_tree_entry *entry;
+	git_oid oid;
+
+	cl_git_pass(git_tree_lookup(&tree, _repo, tid));
+	cl_assert_equal_i(1, git_tree_entrycount(tree));
+	entry = git_tree_entry_byindex(tree, 0);
+
+	cl_git_pass(git_oid_fromstr(&oid, expected_sha));
+
+	cl_assert_equal_i(0, git_oid_cmp(&oid, git_tree_entry_id(entry)));
+	cl_assert_equal_i(expected_filemode, git_tree_entry_filemode(entry));
+
+	git_tree_free(tree);
+}
+
+static void tree_creator(git_oid *out, void (*fn)(git_treebuilder *))
+{
+	git_treebuilder *builder;
+
+	cl_git_pass(git_treebuilder_create(&builder, NULL));
+
+	fn(builder);
+
+	cl_git_pass(git_treebuilder_write(out, _repo, builder));
+	git_treebuilder_free(builder);
+}
+
+static void two_blobs(git_treebuilder *bld)
+{
+	git_oid oid;
+	const git_tree_entry *entry;
+	
+	cl_git_pass(git_oid_fromstr(&oid,
+		"a8233120f6ad708f843d861ce2b7228ec4e3dec6"));	/* blob oid (README) */
+
+	cl_git_pass(git_treebuilder_insert(
+		&entry,	bld, "duplicate", &oid,
+		GIT_FILEMODE_BLOB));
+
+	cl_git_pass(git_oid_fromstr(&oid,
+		"a71586c1dfe8a71c6cbf6c129f404c5642ff31bd"));	/* blob oid (new.txt) */
+
+	cl_git_pass(git_treebuilder_insert(
+		&entry,	bld, "duplicate", &oid,
+		GIT_FILEMODE_BLOB));
+}
+
+static void one_blob_and_one_tree(git_treebuilder *bld)
+{
+	git_oid oid;
+	const git_tree_entry *entry;
+	
+	cl_git_pass(git_oid_fromstr(&oid,
+		"a8233120f6ad708f843d861ce2b7228ec4e3dec6"));	/* blob oid (README) */
+
+	cl_git_pass(git_treebuilder_insert(
+		&entry,	bld, "duplicate", &oid,
+		GIT_FILEMODE_BLOB));
+
+	cl_git_pass(git_oid_fromstr(&oid,
+		"4e0883eeeeebc1fb1735161cea82f7cb5fab7e63"));	/* tree oid (a) */
+
+	cl_git_pass(git_treebuilder_insert(
+		&entry,	bld, "duplicate", &oid,
+		GIT_FILEMODE_TREE));
+}
+
+void test_object_tree_duplicateentries__cannot_create_a_duplicate_entry_through_the_treebuilder(void)
+{
+	git_oid tid;
+
+	tree_creator(&tid, two_blobs);
+	tree_checker(&tid, "a71586c1dfe8a71c6cbf6c129f404c5642ff31bd", GIT_FILEMODE_BLOB);
+	
+	tree_creator(&tid, one_blob_and_one_tree);
+	tree_checker(&tid, "4e0883eeeeebc1fb1735161cea82f7cb5fab7e63", GIT_FILEMODE_TREE);
+}