thodg/libgit2

diff --git a/src/diff.c b/src/diff.c
index cb05a5f..0d1aed4 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -318,6 +318,31 @@ static const char *diff_mnemonic_prefix(
 	return pfx;
 }
 
+static void diff_set_ignore_case(git_diff *diff, bool ignore_case)
+{
+	if (!ignore_case) {
+		diff->opts.flags &= ~GIT_DIFF_IGNORE_CASE;
+
+		diff->strcomp    = git__strcmp;
+		diff->strncomp   = git__strncmp;
+		diff->pfxcomp    = git__prefixcmp;
+		diff->entrycomp  = git_index_entry_cmp;
+
+		git_vector_set_cmp(&diff->deltas, git_diff_delta__cmp);
+	} else {
+		diff->opts.flags |= GIT_DIFF_IGNORE_CASE;
+
+		diff->strcomp    = git__strcasecmp;
+		diff->strncomp   = git__strncasecmp;
+		diff->pfxcomp    = git__prefixcmp_icase;
+		diff->entrycomp  = git_index_entry_icmp;
+
+		git_vector_set_cmp(&diff->deltas, git_diff_delta__casecmp);
+	}
+
+	git_vector_sort(&diff->deltas);
+}
+
 static git_diff *diff_list_alloc(
 	git_repository *repo,
 	git_iterator *old_iter,
@@ -344,24 +369,10 @@ static git_diff *diff_list_alloc(
 
 	/* Use case-insensitive compare if either iterator has
 	 * the ignore_case bit set */
-	if (!git_iterator_ignore_case(old_iter) &&
-		!git_iterator_ignore_case(new_iter)) {
-		diff->opts.flags &= ~GIT_DIFF_IGNORE_CASE;
-
-		diff->strcomp    = git__strcmp;
-		diff->strncomp   = git__strncmp;
-		diff->pfxcomp    = git__prefixcmp;
-		diff->entrycomp  = git_index_entry__cmp;
-	} else {
-		diff->opts.flags |= GIT_DIFF_IGNORE_CASE;
-
-		diff->strcomp    = git__strcasecmp;
-		diff->strncomp   = git__strncasecmp;
-		diff->pfxcomp    = git__prefixcmp_icase;
-		diff->entrycomp  = git_index_entry__cmp_icase;
-
-		git_vector_set_cmp(&diff->deltas, git_diff_delta__casecmp);
-	}
+	diff_set_ignore_case(
+		diff,
+		git_iterator_ignore_case(old_iter) ||
+		git_iterator_ignore_case(new_iter));
 
 	return diff;
 }
@@ -1183,39 +1194,25 @@ int git_diff_tree_to_index(
 	const git_diff_options *opts)
 {
 	int error = 0;
-	bool reset_index_ignore_case = false;
+	bool index_ignore_case = false;
 
 	assert(diff && repo);
 
 	if (!index && (error = diff_load_index(&index, repo)) < 0)
 		return error;
 
-	if (index->ignore_case) {
-		git_index__set_ignore_case(index, false);
-		reset_index_ignore_case = true;
-	}
+	index_ignore_case = index->ignore_case;
 
 	DIFF_FROM_ITERATORS(
-		git_iterator_for_tree(&a, old_tree, 0, pfx, pfx),
-		git_iterator_for_index(&b, index, 0, pfx, pfx)
+		git_iterator_for_tree(
+			&a, old_tree, GIT_ITERATOR_DONT_IGNORE_CASE, pfx, pfx),
+		git_iterator_for_index(
+			&b, index, GIT_ITERATOR_DONT_IGNORE_CASE, pfx, pfx)
 	);
 
-	if (reset_index_ignore_case) {
-		git_index__set_ignore_case(index, true);
-
-		if (!error) {
-			git_diff *d = *diff;
-
-			d->opts.flags |= GIT_DIFF_IGNORE_CASE;
-			d->strcomp    = git__strcasecmp;
-			d->strncomp   = git__strncasecmp;
-			d->pfxcomp    = git__prefixcmp_icase;
-			d->entrycomp  = git_index_entry__cmp_icase;
-
-			git_vector_set_cmp(&d->deltas, git_diff_delta__casecmp);
-			git_vector_sort(&d->deltas);
-		}
-	}
+	/* if index is in case-insensitive order, re-sort deltas to match */
+	if (!error && index_ignore_case)
+		diff_set_ignore_case(*diff, true);
 
 	return error;
 }
diff --git a/src/index.c b/src/index.c
index f28cbef..d733e4e 100644
--- a/src/index.c
+++ b/src/index.c
@@ -106,7 +106,7 @@ static int write_index(git_index *index, git_filebuf *file);
 static void index_entry_free(git_index_entry *entry);
 static void index_entry_reuc_free(git_index_reuc_entry *reuc);
 
-static int index_srch(const void *key, const void *array_member)
+int git_index_entry_srch(const void *key, const void *array_member)
 {
 	const struct entry_srch_key *srch_key = key;
 	const git_index_entry *entry = array_member;
@@ -131,7 +131,7 @@ static int index_srch(const void *key, const void *array_member)
 	return 0;
 }
 
-static int index_isrch(const void *key, const void *array_member)
+int git_index_entry_isrch(const void *key, const void *array_member)
 {
 	const struct entry_srch_key *srch_key = key;
 	const git_index_entry *entry = array_member;
@@ -157,31 +157,21 @@ static int index_isrch(const void *key, const void *array_member)
 	return 0;
 }
 
-static int index_cmp_path(const void *a, const void *b)
-{
-	return strcmp((const char *)a, (const char *)b);
-}
-
-static int index_icmp_path(const void *a, const void *b)
-{
-	return strcasecmp((const char *)a, (const char *)b);
-}
-
-static int index_srch_path(const void *path, const void *array_member)
+static int index_entry_srch_path(const void *path, const void *array_member)
 {
 	const git_index_entry *entry = array_member;
 
 	return strcmp((const char *)path, entry->path);
 }
 
-static int index_isrch_path(const void *path, const void *array_member)
+static int index_entry_isrch_path(const void *path, const void *array_member)
 {
 	const git_index_entry *entry = array_member;
 
 	return strcasecmp((const char *)path, entry->path);
 }
 
-static int index_cmp(const void *a, const void *b)
+int git_index_entry_cmp(const void *a, const void *b)
 {
 	int diff;
 	const git_index_entry *entry_a = a;
@@ -195,7 +185,7 @@ static int index_cmp(const void *a, const void *b)
 	return diff;
 }
 
-static int index_icmp(const void *a, const void *b)
+int git_index_entry_icmp(const void *a, const void *b)
 {
 	int diff;
 	const git_index_entry *entry_a = a;
@@ -351,15 +341,22 @@ void git_index__set_ignore_case(git_index *index, bool ignore_case)
 {
 	index->ignore_case = ignore_case;
 
-	index->entries_cmp_path = ignore_case ? index_icmp_path : index_cmp_path;
-	index->entries_search = ignore_case ? index_isrch : index_srch;
-	index->entries_search_path = ignore_case ? index_isrch_path : index_srch_path;
+	if (ignore_case) {
+		index->entries_cmp_path    = git__strcasecmp_cb;
+		index->entries_search      = git_index_entry_isrch;
+		index->entries_search_path = index_entry_isrch_path;
+		index->reuc_search         = reuc_isrch;
+	} else {
+		index->entries_cmp_path    = git__strcmp_cb;
+		index->entries_search      = git_index_entry_srch;
+		index->entries_search_path = index_entry_srch_path;
+		index->reuc_search         = reuc_srch;
+	}
 
-	git_vector_set_cmp(&index->entries, ignore_case ? index_icmp : index_cmp);
+	git_vector_set_cmp(&index->entries,
+		ignore_case ? git_index_entry_icmp : git_index_entry_cmp);
 	index_sort_if_needed(index, true);
 
-	index->reuc_search = ignore_case ? reuc_isrch : reuc_srch;
-
 	git_vector_set_cmp(&index->reuc, ignore_case ? reuc_icmp : reuc_cmp);
 	git_vector_sort(&index->reuc);
 }
@@ -390,15 +387,15 @@ int git_index_open(git_index **index_out, const char *index_path)
 			index->on_disk = 1;
 	}
 
-	if (git_vector_init(&index->entries, 32, index_cmp) < 0 ||
+	if (git_vector_init(&index->entries, 32, git_index_entry_cmp) < 0 ||
 		git_vector_init(&index->names, 32, conflict_name_cmp) < 0 ||
 		git_vector_init(&index->reuc, 32, reuc_cmp) < 0 ||
-		git_vector_init(&index->deleted, 2, index_cmp) < 0)
+		git_vector_init(&index->deleted, 2, git_index_entry_cmp) < 0)
 		goto fail;
 
-	index->entries_cmp_path = index_cmp_path;
-	index->entries_search = index_srch;
-	index->entries_search_path = index_srch_path;
+	index->entries_cmp_path = git__strcmp_cb;
+	index->entries_search = git_index_entry_srch;
+	index->entries_search_path = index_entry_srch_path;
 	index->reuc_search = reuc_srch;
 
 	if (index_path != NULL && (error = git_index_read(index, true)) < 0)
@@ -727,22 +724,6 @@ void git_index_entry__init_from_stat(
 	entry->file_size = st->st_size;
 }
 
-int git_index_entry__cmp(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcmp(entry_a->path, entry_b->path);
-}
-
-int git_index_entry__cmp_icase(const void *a, const void *b)
-{
-	const git_index_entry *entry_a = a;
-	const git_index_entry *entry_b = b;
-
-	return strcasecmp(entry_a->path, entry_b->path);
-}
-
 static int index_entry_init(
 	git_index_entry **entry_out, git_index *index, const char *rel_path)
 {
@@ -1129,14 +1110,14 @@ int git_index_remove_directory(git_index *index, const char *dir, int stage)
 }
 
 int git_index__find_in_entries(
-	size_t *out, git_vector *entries, git_vector_cmp entry_cmp,
+	size_t *out, git_vector *entries, git_vector_cmp entry_srch,
 	const char *path, size_t path_len, int stage)
 {
 	struct entry_srch_key srch_key;
 	srch_key.path = path;
 	srch_key.path_len = !path_len ? strlen(path) : path_len;
 	srch_key.stage = stage;
-	return git_vector_bsearch2(out, entries, entry_cmp, &srch_key);
+	return git_vector_bsearch2(out, entries, entry_srch, &srch_key);
 }
 
 int git_index__find(
@@ -2040,7 +2021,7 @@ static int write_entries(git_index *index, git_filebuf *file)
 	/* If index->entries is sorted case-insensitively, then we need
 	 * to re-sort it case-sensitively before writing */
 	if (index->ignore_case) {
-		git_vector_dup(&case_sorted, &index->entries, index_cmp);
+		git_vector_dup(&case_sorted, &index->entries, git_index_entry_cmp);
 		git_vector_sort(&case_sorted);
 		entries = &case_sorted;
 	} else {
diff --git a/src/index.h b/src/index.h
index c2a9322..cb44258 100644
--- a/src/index.h
+++ b/src/index.h
@@ -53,8 +53,13 @@ struct git_index_conflict_iterator {
 extern void git_index_entry__init_from_stat(
 	git_index_entry *entry, struct stat *st, bool trust_mode);
 
-extern int git_index_entry__cmp(const void *a, const void *b);
-extern int git_index_entry__cmp_icase(const void *a, const void *b);
+/* Index entry comparison functions for array sorting */
+extern int git_index_entry_cmp(const void *a, const void *b);
+extern int git_index_entry_icmp(const void *a, const void *b);
+
+/* Index entry search functions for search using a search spec */
+extern int git_index_entry_srch(const void *a, const void *b);
+extern int git_index_entry_isrch(const void *a, const void *b);
 
 /* Search index for `path`, returning GIT_ENOTFOUND if it does not exist.
  * `at_pos` is set to the position where it is or would be inserted.
@@ -83,7 +88,7 @@ extern void git_index__release_snapshot(git_index *index);
 /* Allow searching in a snapshot; entries must already be sorted! */
 extern int git_index__find_in_entries(
 	size_t *at_pos,
-	git_vector *entries, git_vector_cmp entry_cmp,
+	git_vector *entries, git_vector_cmp entry_srch,
 	const char *path, size_t path_len, int stage);
 
 #endif
diff --git a/src/iterator.c b/src/iterator.c
index a84f4d3..53ef278 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -868,16 +868,20 @@ int git_iterator_for_index(
 		return error;
 	}
 	ii->index = index;
-	ii->entry_srch = index->entries_search;
 
 	ITERATOR_BASE_INIT(ii, index, INDEX, git_index_owner(index));
 
-	if (index->ignore_case) {
-		ii->base.flags |= GIT_ITERATOR_IGNORE_CASE;
-		ii->base.prefixcomp = git__prefixcmp_icase;
+	if ((error = iterator__update_ignore_case((git_iterator *)ii, flags)) < 0) {
+		git_iterator_free((git_iterator *)ii);
+		return error;
 	}
 
-	/* TODO: resort entries to match desired ignore_case behavior */
+	ii->entry_srch = iterator__ignore_case(ii) ?
+		git_index_entry_isrch : git_index_entry_srch;
+
+	git_vector_set_cmp(&ii->entries, iterator__ignore_case(ii) ?
+		git_index_entry_icmp : git_index_entry_cmp);
+	git_vector_sort(&ii->entries);
 
 	git_buf_init(&ii->partial, 0);
 	ii->tree_entry.mode = GIT_FILEMODE_TREE;
diff --git a/src/merge.c b/src/merge.c
index 9c4a07b..68105d4 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -1332,7 +1332,7 @@ int git_merge_diff_list__find_differences(
 {
 	git_iterator *iterators[3] = {0};
 	const git_index_entry *items[3] = {0}, *best_cur_item, *cur_items[3];
-	git_vector_cmp entry_compare = git_index_entry__cmp;
+	git_vector_cmp entry_compare = git_index_entry_cmp;
 	struct merge_diff_df_data df_data = {0};
 	int cur_item_modified;
 	size_t i, j;
diff --git a/src/util.c b/src/util.c
index 3767b89..3985825 100644
--- a/src/util.c
+++ b/src/util.c
@@ -542,10 +542,12 @@ int git__bsearch_r(
  */
 int git__strcmp_cb(const void *a, const void *b)
 {
-	const char *stra = (const char *)a;
-	const char *strb = (const char *)b;
+	return strcmp((const char *)a, (const char *)b);
+}
 
-	return strcmp(stra, strb);
+int git__strcasecmp_cb(const void *a, const void *b)
+{
+	return strcasecmp((const char *)a, (const char *)b);
 }
 
 int git__parse_bool(int *out, const char *value)
diff --git a/src/util.h b/src/util.h
index 5c2c563..d94463c 100644
--- a/src/util.h
+++ b/src/util.h
@@ -196,6 +196,7 @@ extern int git__bsearch_r(
 	size_t *position);
 
 extern int git__strcmp_cb(const void *a, const void *b);
+extern int git__strcasecmp_cb(const void *a, const void *b);
 
 extern int git__strcmp(const char *a, const char *b);
 extern int git__strcasecmp(const char *a, const char *b);
diff --git a/src/vector.c b/src/vector.c
index 9f7eed5..c769b69 100644
--- a/src/vector.c
+++ b/src/vector.c
@@ -177,7 +177,8 @@ void git_vector_sort(git_vector *v)
 	if (git_vector_is_sorted(v) || !v->_cmp)
 		return;
 
-	git__tsort(v->contents, v->length, v->_cmp);
+	if (v->length > 1)
+		git__tsort(v->contents, v->length, v->_cmp);
 	git_vector_set_sorted(v, 1);
 }
 
diff --git a/tests/diff/iterator.c b/tests/diff/iterator.c
index 891d8a6..19a9a00 100644
--- a/tests/diff/iterator.c
+++ b/tests/diff/iterator.c
@@ -355,6 +355,7 @@ static void index_iterator_test(
 	const char *sandbox,
 	const char *start,
 	const char *end,
+	git_iterator_flag_t flags,
 	int expected_count,
 	const char **expected_names,
 	const char **expected_oids)
@@ -364,9 +365,12 @@ static void index_iterator_test(
 	const git_index_entry *entry;
 	int error, count = 0;
 	git_repository *repo = cl_git_sandbox_init(sandbox);
+	unsigned int caps;
 
 	cl_git_pass(git_repository_index(&index, repo));
-	cl_git_pass(git_iterator_for_index(&i, index, 0, start, end));
+	caps = git_index_caps(index);
+
+	cl_git_pass(git_iterator_for_index(&i, index, flags, start, end));
 
 	while (!(error = git_iterator_advance(&entry, i))) {
 		cl_assert(entry);
@@ -388,6 +392,8 @@ static void index_iterator_test(
 	cl_assert_equal_i(expected_count, count);
 
 	git_iterator_free(i);
+
+	cl_assert(caps == git_index_caps(index));
 	git_index_free(index);
 }
 
@@ -446,7 +452,8 @@ static const char *expected_index_oids_0[] = {
 void test_diff_iterator__index_0(void)
 {
 	index_iterator_test(
-		"attr", NULL, NULL, 23, expected_index_0, expected_index_oids_0);
+		"attr", NULL, NULL, 0, ARRAY_SIZE(expected_index_0),
+		expected_index_0, expected_index_oids_0);
 }
 
 static const char *expected_index_range[] = {
@@ -466,25 +473,26 @@ static const char *expected_index_oids_range[] = {
 void test_diff_iterator__index_range(void)
 {
 	index_iterator_test(
-		"attr", "root", "root", 4, expected_index_range, expected_index_oids_range);
+		"attr", "root", "root", 0, ARRAY_SIZE(expected_index_range),
+		expected_index_range, expected_index_oids_range);
 }
 
 void test_diff_iterator__index_range_empty_0(void)
 {
 	index_iterator_test(
-		"attr", "empty", "empty", 0, NULL, NULL);
+		"attr", "empty", "empty", 0, 0, NULL, NULL);
 }
 
 void test_diff_iterator__index_range_empty_1(void)
 {
 	index_iterator_test(
-		"attr", "z_empty_after", NULL, 0, NULL, NULL);
+		"attr", "z_empty_after", NULL, 0, 0, NULL, NULL);
 }
 
 void test_diff_iterator__index_range_empty_2(void)
 {
 	index_iterator_test(
-		"attr", NULL, ".aaa_empty_before", 0, NULL, NULL);
+		"attr", NULL, ".aaa_empty_before", 0, 0, NULL, NULL);
 }
 
 static const char *expected_index_1[] = {
@@ -522,9 +530,45 @@ static const char* expected_index_oids_1[] = {
 void test_diff_iterator__index_1(void)
 {
 	index_iterator_test(
-		"status", NULL, NULL, 13, expected_index_1, expected_index_oids_1);
+		"status", NULL, NULL, 0, ARRAY_SIZE(expected_index_1),
+		expected_index_1, expected_index_oids_1);
 }
 
+static const char *expected_index_cs[] = {
+	"B", "D", "F", "H", "J", "L/1", "L/B", "L/D", "L/a", "L/c",
+	"a", "c", "e", "g", "i", "k/1", "k/B", "k/D", "k/a", "k/c",
+};
+
+static const char *expected_index_ci[] = {
+	"a", "B", "c", "D", "e", "F", "g", "H", "i", "J",
+	"k/1", "k/a", "k/B", "k/c", "k/D", "L/1", "L/a", "L/B", "L/c", "L/D",
+};
+
+void test_diff_iterator__index_case_folding(void)
+{
+	git_buf path = GIT_BUF_INIT;
+	int fs_is_ci = 0;
+
+	cl_git_pass(git_buf_joinpath(&path, cl_fixture("icase"), ".gitted/CoNfIg"));
+	fs_is_ci = git_path_exists(path.ptr);
+	git_buf_free(&path);
+
+	index_iterator_test(
+		"icase", NULL, NULL, 0, ARRAY_SIZE(expected_index_cs),
+		fs_is_ci ? expected_index_ci : expected_index_cs, NULL);
+
+	cl_git_sandbox_cleanup();
+
+	index_iterator_test(
+		"icase", NULL, NULL, GIT_ITERATOR_IGNORE_CASE,
+		ARRAY_SIZE(expected_index_ci), expected_index_ci, NULL);
+
+	cl_git_sandbox_cleanup();
+
+	index_iterator_test(
+		"icase", NULL, NULL, GIT_ITERATOR_DONT_IGNORE_CASE,
+		ARRAY_SIZE(expected_index_cs), expected_index_cs, NULL);
+}
 
 /* -- WORKDIR ITERATOR TESTS -- */