diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 3ce7541783..6034408d48 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -87,9 +87,9 @@ static int debug_merge(const struct cache_entry * const *stages,
 {
 	int i;
 
-	printf("* %d-way merge\n", o->merge_size);
+	printf("* %d-way merge\n", o->internal.merge_size);
 	debug_stage("index", stages[0], o);
-	for (i = 1; i <= o->merge_size; i++) {
+	for (i = 1; i <= o->internal.merge_size; i++) {
 		char buf[24];
 		xsnprintf(buf, sizeof(buf), "ent#%d", i);
 		debug_stage(buf, stages[i], o);
@@ -144,7 +144,7 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
 		OPT__DRY_RUN(&opts.dry_run, N_("don't update the index or the work tree")),
 		OPT_BOOL(0, "no-sparse-checkout", &opts.skip_sparse_checkout,
 			 N_("skip applying sparse checkout filter")),
-		OPT_BOOL(0, "debug-unpack", &opts.debug_unpack,
+		OPT_BOOL(0, "debug-unpack", &opts.internal.debug_unpack,
 			 N_("debug unpack-trees")),
 		OPT_CALLBACK_F(0, "recurse-submodules", NULL,
 			    "checkout", "control recursive updating of submodules",
@@ -247,7 +247,7 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
 			opts.head_idx = 1;
 	}
 
-	if (opts.debug_unpack)
+	if (opts.internal.debug_unpack)
 		opts.fn = debug_merge;
 
 	/* If we're going to prime_cache_tree later, skip cache tree update */
@@ -263,7 +263,7 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
 	if (unpack_trees(nr_trees, t, &opts))
 		return 128;
 
-	if (opts.debug_unpack || opts.dry_run)
+	if (opts.internal.debug_unpack || opts.dry_run)
 		return 0; /* do not write the index out */
 
 	/*
diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
index c373815491..8d5ae6f2a6 100644
--- a/builtin/sparse-checkout.c
+++ b/builtin/sparse-checkout.c
@@ -217,16 +217,14 @@ static int update_working_directory(struct pattern_list *pl)
 	o.head_idx = -1;
 	o.src_index = r->index;
 	o.dst_index = r->index;
-	index_state_init(&o.result, r);
 	o.skip_sparse_checkout = 0;
-	o.pl = pl;
 
 	setup_work_tree();
 
 	repo_hold_locked_index(r, &lock_file, LOCK_DIE_ON_ERROR);
 
 	setup_unpack_trees_porcelain(&o, "sparse-checkout");
-	result = update_sparsity(&o);
+	result = update_sparsity(&o, pl);
 	clear_unpack_trees_porcelain(&o);
 
 	if (result == UPDATE_SPARSITY_WARNINGS)
diff --git a/dir.c b/dir.c
index 4e99f0c868..7adf242026 100644
--- a/dir.c
+++ b/dir.c
@@ -1190,7 +1190,7 @@ struct pattern_list *add_pattern_list(struct dir_struct *dir,
 	struct pattern_list *pl;
 	struct exclude_list_group *group;
 
-	group = &dir->exclude_list_group[group_type];
+	group = &dir->internal.exclude_list_group[group_type];
 	ALLOC_GROW(group->pl, group->nr + 1, group->alloc);
 	pl = &group->pl[group->nr++];
 	memset(pl, 0, sizeof(*pl));
@@ -1211,7 +1211,7 @@ static void add_patterns_from_file_1(struct dir_struct *dir, const char *fname,
 	 * differently when dir->untracked is non-NULL.
 	 */
 	if (!dir->untracked)
-		dir->unmanaged_exclude_files++;
+		dir->internal.unmanaged_exclude_files++;
 	pl = add_pattern_list(dir, EXC_FILE, fname);
 	if (add_patterns(fname, "", 0, pl, NULL, 0, oid_stat) < 0)
 		die(_("cannot use %s as an exclude file"), fname);
@@ -1219,7 +1219,7 @@ static void add_patterns_from_file_1(struct dir_struct *dir, const char *fname,
 
 void add_patterns_from_file(struct dir_struct *dir, const char *fname)
 {
-	dir->unmanaged_exclude_files++; /* see validate_untracked_cache() */
+	dir->internal.unmanaged_exclude_files++; /* see validate_untracked_cache() */
 	add_patterns_from_file_1(dir, fname, NULL);
 }
 
@@ -1519,7 +1519,7 @@ static struct path_pattern *last_matching_pattern_from_lists(
 	struct exclude_list_group *group;
 	struct path_pattern *pattern;
 	for (i = EXC_CMDL; i <= EXC_FILE; i++) {
-		group = &dir->exclude_list_group[i];
+		group = &dir->internal.exclude_list_group[i];
 		for (j = group->nr - 1; j >= 0; j--) {
 			pattern = last_matching_pattern_from_list(
 				pathname, pathlen, basename, dtype_p,
@@ -1545,20 +1545,20 @@ static void prep_exclude(struct dir_struct *dir,
 	struct untracked_cache_dir *untracked;
 	int current;
 
-	group = &dir->exclude_list_group[EXC_DIRS];
+	group = &dir->internal.exclude_list_group[EXC_DIRS];
 
 	/*
 	 * Pop the exclude lists from the EXCL_DIRS exclude_list_group
 	 * which originate from directories not in the prefix of the
 	 * path being checked.
 	 */
-	while ((stk = dir->exclude_stack) != NULL) {
+	while ((stk = dir->internal.exclude_stack) != NULL) {
 		if (stk->baselen <= baselen &&
-		    !strncmp(dir->basebuf.buf, base, stk->baselen))
+		    !strncmp(dir->internal.basebuf.buf, base, stk->baselen))
 			break;
-		pl = &group->pl[dir->exclude_stack->exclude_ix];
-		dir->exclude_stack = stk->prev;
-		dir->pattern = NULL;
+		pl = &group->pl[dir->internal.exclude_stack->exclude_ix];
+		dir->internal.exclude_stack = stk->prev;
+		dir->internal.pattern = NULL;
 		free((char *)pl->src); /* see strbuf_detach() below */
 		clear_pattern_list(pl);
 		free(stk);
@@ -1566,7 +1566,7 @@ static void prep_exclude(struct dir_struct *dir,
 	}
 
 	/* Skip traversing into sub directories if the parent is excluded */
-	if (dir->pattern)
+	if (dir->internal.pattern)
 		return;
 
 	/*
@@ -1574,12 +1574,12 @@ static void prep_exclude(struct dir_struct *dir,
 	 * memset(dir, 0, sizeof(*dir)) before use. Changing all of
 	 * them seems lots of work for little benefit.
 	 */
-	if (!dir->basebuf.buf)
-		strbuf_init(&dir->basebuf, PATH_MAX);
+	if (!dir->internal.basebuf.buf)
+		strbuf_init(&dir->internal.basebuf, PATH_MAX);
 
 	/* Read from the parent directories and push them down. */
 	current = stk ? stk->baselen : -1;
-	strbuf_setlen(&dir->basebuf, current < 0 ? 0 : current);
+	strbuf_setlen(&dir->internal.basebuf, current < 0 ? 0 : current);
 	if (dir->untracked)
 		untracked = stk ? stk->ucd : dir->untracked->root;
 	else
@@ -1599,32 +1599,33 @@ static void prep_exclude(struct dir_struct *dir,
 				die("oops in prep_exclude");
 			cp++;
 			untracked =
-				lookup_untracked(dir->untracked, untracked,
+				lookup_untracked(dir->untracked,
+						 untracked,
 						 base + current,
 						 cp - base - current);
 		}
-		stk->prev = dir->exclude_stack;
+		stk->prev = dir->internal.exclude_stack;
 		stk->baselen = cp - base;
 		stk->exclude_ix = group->nr;
 		stk->ucd = untracked;
 		pl = add_pattern_list(dir, EXC_DIRS, NULL);
-		strbuf_add(&dir->basebuf, base + current, stk->baselen - current);
-		assert(stk->baselen == dir->basebuf.len);
+		strbuf_add(&dir->internal.basebuf, base + current, stk->baselen - current);
+		assert(stk->baselen == dir->internal.basebuf.len);
 
 		/* Abort if the directory is excluded */
 		if (stk->baselen) {
 			int dt = DT_DIR;
-			dir->basebuf.buf[stk->baselen - 1] = 0;
-			dir->pattern = last_matching_pattern_from_lists(dir,
+			dir->internal.basebuf.buf[stk->baselen - 1] = 0;
+			dir->internal.pattern = last_matching_pattern_from_lists(dir,
 									istate,
-				dir->basebuf.buf, stk->baselen - 1,
-				dir->basebuf.buf + current, &dt);
-			dir->basebuf.buf[stk->baselen - 1] = '/';
-			if (dir->pattern &&
-			    dir->pattern->flags & PATTERN_FLAG_NEGATIVE)
-				dir->pattern = NULL;
-			if (dir->pattern) {
-				dir->exclude_stack = stk;
+				dir->internal.basebuf.buf, stk->baselen - 1,
+				dir->internal.basebuf.buf + current, &dt);
+			dir->internal.basebuf.buf[stk->baselen - 1] = '/';
+			if (dir->internal.pattern &&
+			    dir->internal.pattern->flags & PATTERN_FLAG_NEGATIVE)
+				dir->internal.pattern = NULL;
+			if (dir->internal.pattern) {
+				dir->internal.exclude_stack = stk;
 				return;
 			}
 		}
@@ -1647,15 +1648,15 @@ static void prep_exclude(struct dir_struct *dir,
 		      */
 		     !is_null_oid(&untracked->exclude_oid))) {
 			/*
-			 * dir->basebuf gets reused by the traversal, but we
-			 * need fname to remain unchanged to ensure the src
-			 * member of each struct path_pattern correctly
+			 * dir->internal.basebuf gets reused by the traversal,
+			 * but we need fname to remain unchanged to ensure the
+			 * src member of each struct path_pattern correctly
 			 * back-references its source file.  Other invocations
 			 * of add_pattern_list provide stable strings, so we
 			 * strbuf_detach() and free() here in the caller.
 			 */
 			struct strbuf sb = STRBUF_INIT;
-			strbuf_addbuf(&sb, &dir->basebuf);
+			strbuf_addbuf(&sb, &dir->internal.basebuf);
 			strbuf_addstr(&sb, dir->exclude_per_dir);
 			pl->src = strbuf_detach(&sb, NULL);
 			add_patterns(pl->src, pl->src, stk->baselen, pl, istate,
@@ -1681,10 +1682,10 @@ static void prep_exclude(struct dir_struct *dir,
 			invalidate_gitignore(dir->untracked, untracked);
 			oidcpy(&untracked->exclude_oid, &oid_stat.oid);
 		}
-		dir->exclude_stack = stk;
+		dir->internal.exclude_stack = stk;
 		current = stk->baselen;
 	}
-	strbuf_setlen(&dir->basebuf, baselen);
+	strbuf_setlen(&dir->internal.basebuf, baselen);
 }
 
 /*
@@ -1704,8 +1705,8 @@ struct path_pattern *last_matching_pattern(struct dir_struct *dir,
 
 	prep_exclude(dir, istate, pathname, basename-pathname);
 
-	if (dir->pattern)
-		return dir->pattern;
+	if (dir->internal.pattern)
+		return dir->internal.pattern;
 
 	return last_matching_pattern_from_lists(dir, istate, pathname, pathlen,
 			basename, dtype_p);
@@ -1742,7 +1743,7 @@ static struct dir_entry *dir_add_name(struct dir_struct *dir,
 	if (index_file_exists(istate, pathname, len, ignore_case))
 		return NULL;
 
-	ALLOC_GROW(dir->entries, dir->nr+1, dir->alloc);
+	ALLOC_GROW(dir->entries, dir->nr+1, dir->internal.alloc);
 	return dir->entries[dir->nr++] = dir_entry_new(pathname, len);
 }
 
@@ -1753,7 +1754,7 @@ struct dir_entry *dir_add_ignored(struct dir_struct *dir,
 	if (!index_name_is_other(istate, pathname, len))
 		return NULL;
 
-	ALLOC_GROW(dir->ignored, dir->ignored_nr+1, dir->ignored_alloc);
+	ALLOC_GROW(dir->ignored, dir->ignored_nr+1, dir->internal.ignored_alloc);
 	return dir->ignored[dir->ignored_nr++] = dir_entry_new(pathname, len);
 }
 
@@ -2569,7 +2570,7 @@ static enum path_treatment read_directory_recursive(struct dir_struct *dir,
 
 	if (open_cached_dir(&cdir, dir, untracked, istate, &path, check_only))
 		goto out;
-	dir->visited_directories++;
+	dir->internal.visited_directories++;
 
 	if (untracked)
 		untracked->check_only = !!check_only;
@@ -2578,7 +2579,7 @@ static enum path_treatment read_directory_recursive(struct dir_struct *dir,
 		/* check how the file or directory should be treated */
 		state = treat_path(dir, untracked, &cdir, istate, &path,
 				   baselen, pathspec);
-		dir->visited_paths++;
+		dir->internal.visited_paths++;
 
 		if (state > dir_state)
 			dir_state = state;
@@ -2586,7 +2587,8 @@ static enum path_treatment read_directory_recursive(struct dir_struct *dir,
 		/* recurse into subdir if instructed by treat_path */
 		if (state == path_recurse) {
 			struct untracked_cache_dir *ud;
-			ud = lookup_untracked(dir->untracked, untracked,
+			ud = lookup_untracked(dir->untracked,
+					      untracked,
 					      path.buf + baselen,
 					      path.len - baselen);
 			subdir_state =
@@ -2846,7 +2848,7 @@ static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *d
 	 * condition also catches running setup_standard_excludes()
 	 * before setting dir->untracked!
 	 */
-	if (dir->unmanaged_exclude_files)
+	if (dir->internal.unmanaged_exclude_files)
 		return NULL;
 
 	/*
@@ -2875,7 +2877,7 @@ static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *d
 	 * EXC_CMDL is not considered in the cache. If people set it,
 	 * skip the cache.
 	 */
-	if (dir->exclude_list_group[EXC_CMDL].nr)
+	if (dir->internal.exclude_list_group[EXC_CMDL].nr)
 		return NULL;
 
 	if (!ident_in_untracked(dir->untracked)) {
@@ -2935,15 +2937,15 @@ static struct untracked_cache_dir *validate_untracked_cache(struct dir_struct *d
 
 	/* Validate $GIT_DIR/info/exclude and core.excludesfile */
 	root = dir->untracked->root;
-	if (!oideq(&dir->ss_info_exclude.oid,
+	if (!oideq(&dir->internal.ss_info_exclude.oid,
 		   &dir->untracked->ss_info_exclude.oid)) {
 		invalidate_gitignore(dir->untracked, root);
-		dir->untracked->ss_info_exclude = dir->ss_info_exclude;
+		dir->untracked->ss_info_exclude = dir->internal.ss_info_exclude;
 	}
-	if (!oideq(&dir->ss_excludes_file.oid,
+	if (!oideq(&dir->internal.ss_excludes_file.oid,
 		   &dir->untracked->ss_excludes_file.oid)) {
 		invalidate_gitignore(dir->untracked, root);
-		dir->untracked->ss_excludes_file = dir->ss_excludes_file;
+		dir->untracked->ss_excludes_file = dir->internal.ss_excludes_file;
 	}
 
 	/* Make sure this directory is not dropped out at saving phase */
@@ -2969,9 +2971,9 @@ static void emit_traversal_statistics(struct dir_struct *dir,
 	}
 
 	trace2_data_intmax("read_directory", repo,
-			   "directories-visited", dir->visited_directories);
+			   "directories-visited", dir->internal.visited_directories);
 	trace2_data_intmax("read_directory", repo,
-			   "paths-visited", dir->visited_paths);
+			   "paths-visited", dir->internal.visited_paths);
 
 	if (!dir->untracked)
 		return;
@@ -2993,8 +2995,8 @@ int read_directory(struct dir_struct *dir, struct index_state *istate,
 	struct untracked_cache_dir *untracked;
 
 	trace2_region_enter("dir", "read_directory", istate->repo);
-	dir->visited_paths = 0;
-	dir->visited_directories = 0;
+	dir->internal.visited_paths = 0;
+	dir->internal.visited_directories = 0;
 
 	if (has_symlink_leading_path(path, len)) {
 		trace2_region_leave("dir", "read_directory", istate->repo);
@@ -3342,14 +3344,14 @@ void setup_standard_excludes(struct dir_struct *dir)
 		excludes_file = xdg_config_home("ignore");
 	if (excludes_file && !access_or_warn(excludes_file, R_OK, 0))
 		add_patterns_from_file_1(dir, excludes_file,
-					 dir->untracked ? &dir->ss_excludes_file : NULL);
+					 dir->untracked ? &dir->internal.ss_excludes_file : NULL);
 
 	/* per repository user preference */
 	if (startup_info->have_repository) {
 		const char *path = git_path_info_exclude();
 		if (!access_or_warn(path, R_OK, 0))
 			add_patterns_from_file_1(dir, path,
-						 dir->untracked ? &dir->ss_info_exclude : NULL);
+						 dir->untracked ? &dir->internal.ss_info_exclude : NULL);
 	}
 }
 
@@ -3405,7 +3407,7 @@ void dir_clear(struct dir_struct *dir)
 	struct dir_struct new = DIR_INIT;
 
 	for (i = EXC_CMDL; i <= EXC_FILE; i++) {
-		group = &dir->exclude_list_group[i];
+		group = &dir->internal.exclude_list_group[i];
 		for (j = 0; j < group->nr; j++) {
 			pl = &group->pl[j];
 			if (i == EXC_DIRS)
@@ -3422,13 +3424,13 @@ void dir_clear(struct dir_struct *dir)
 	free(dir->ignored);
 	free(dir->entries);
 
-	stk = dir->exclude_stack;
+	stk = dir->internal.exclude_stack;
 	while (stk) {
 		struct exclude_stack *prev = stk->prev;
 		free(stk);
 		stk = prev;
 	}
-	strbuf_release(&dir->basebuf);
+	strbuf_release(&dir->internal.basebuf);
 
 	memcpy(dir, &new, sizeof(*dir));
 }
diff --git a/dir.h b/dir.h
index 8acfc04418..e8106e1eca 100644
--- a/dir.h
+++ b/dir.h
@@ -212,17 +212,6 @@ struct untracked_cache {
  */
 struct dir_struct {
 
-	/* The number of members in `entries[]` array. */
-	int nr;
-
-	/* Internal use; keeps track of allocation of `entries[]` array.*/
-	int alloc;
-
-	/* The number of members in `ignored[]` array. */
-	int ignored_nr;
-
-	int ignored_alloc;
-
 	/* bit-field of options */
 	enum {
 
@@ -287,60 +276,81 @@ struct dir_struct {
 		DIR_SKIP_NESTED_GIT = 1<<9
 	} flags;
 
+	/* The number of members in `entries[]` array. */
+	int nr; /* output only */
+
+	/* The number of members in `ignored[]` array. */
+	int ignored_nr; /* output only */
+
 	/* An array of `struct dir_entry`, each element of which describes a path. */
-	struct dir_entry **entries;
+	struct dir_entry **entries; /* output only */
 
 	/**
 	 * used for ignored paths with the `DIR_SHOW_IGNORED_TOO` and
 	 * `DIR_COLLECT_IGNORED` flags.
 	 */
-	struct dir_entry **ignored;
+	struct dir_entry **ignored; /* output only */
+
+	/* Enable/update untracked file cache if set */
+	struct untracked_cache *untracked;
 
 	/**
-	 * The name of the file to be read in each directory for excluded files
-	 * (typically `.gitignore`).
+	 * Deprecated: ls-files is the only allowed caller; all other callers
+	 * should leave this as NULL; it pre-dated the
+	 * setup_standard_excludes() mechanism that replaces this.
+	 *
+	 * This field tracks the name of the file to be read in each directory
+	 * for excluded files (typically `.gitignore`).
 	 */
 	const char *exclude_per_dir;
 
-	/*
-	 * We maintain three groups of exclude pattern lists:
-	 *
-	 * EXC_CMDL lists patterns explicitly given on the command line.
-	 * EXC_DIRS lists patterns obtained from per-directory ignore files.
-	 * EXC_FILE lists patterns from fallback ignore files, e.g.
-	 *   - .git/info/exclude
-	 *   - core.excludesfile
-	 *
-	 * Each group contains multiple exclude lists, a single list
-	 * per source.
-	 */
+	struct dir_struct_internal {
+		/* Keeps track of allocation of `entries[]` array.*/
+		int alloc;
+
+		/* Keeps track of allocation of `ignored[]` array. */
+		int ignored_alloc;
+
+		/*
+		 * We maintain three groups of exclude pattern lists:
+		 *
+		 * EXC_CMDL lists patterns explicitly given on the command line.
+		 * EXC_DIRS lists patterns obtained from per-directory ignore
+		 *          files.
+		 * EXC_FILE lists patterns from fallback ignore files, e.g.
+		 *   - .git/info/exclude
+		 *   - core.excludesfile
+		 *
+		 * Each group contains multiple exclude lists, a single list
+		 * per source.
+		 */
 #define EXC_CMDL 0
 #define EXC_DIRS 1
 #define EXC_FILE 2
-	struct exclude_list_group exclude_list_group[3];
+		struct exclude_list_group exclude_list_group[3];
 
-	/*
-	 * Temporary variables which are used during loading of the
-	 * per-directory exclude lists.
-	 *
-	 * exclude_stack points to the top of the exclude_stack, and
-	 * basebuf contains the full path to the current
-	 * (sub)directory in the traversal. Exclude points to the
-	 * matching exclude struct if the directory is excluded.
-	 */
-	struct exclude_stack *exclude_stack;
-	struct path_pattern *pattern;
-	struct strbuf basebuf;
+		/*
+		 * Temporary variables which are used during loading of the
+		 * per-directory exclude lists.
+		 *
+		 * exclude_stack points to the top of the exclude_stack, and
+		 * basebuf contains the full path to the current
+		 * (sub)directory in the traversal. Exclude points to the
+		 * matching exclude struct if the directory is excluded.
+		 */
+		struct exclude_stack *exclude_stack;
+		struct path_pattern *pattern;
+		struct strbuf basebuf;
 
-	/* Enable untracked file cache if set */
-	struct untracked_cache *untracked;
-	struct oid_stat ss_info_exclude;
-	struct oid_stat ss_excludes_file;
-	unsigned unmanaged_exclude_files;
+		/* Additional metadata related to 'untracked' */
+		struct oid_stat ss_info_exclude;
+		struct oid_stat ss_excludes_file;
+		unsigned unmanaged_exclude_files;
 
-	/* Stats about the traversal */
-	unsigned visited_paths;
-	unsigned visited_directories;
+		/* Stats about the traversal */
+		unsigned visited_paths;
+		unsigned visited_directories;
+	} internal;
 };
 
 #define DIR_INIT { 0 }
diff --git a/t/t2021-checkout-overwrite.sh b/t/t2021-checkout-overwrite.sh
index 713c3fa603..034f62c13c 100755
--- a/t/t2021-checkout-overwrite.sh
+++ b/t/t2021-checkout-overwrite.sh
@@ -50,10 +50,13 @@ test_expect_success 'checkout commit with dir must not remove untracked a/b' '
 
 test_expect_success SYMLINKS 'the symlink remained' '
 
-	test_when_finished "rm a/b" &&
 	test -h a/b
 '
 
+test_expect_success 'cleanup after previous symlink tests' '
+	rm a/b
+'
+
 test_expect_success SYMLINKS 'checkout -f must not follow symlinks when removing entries' '
 	git checkout -f start &&
 	mkdir dir &&
@@ -66,4 +69,15 @@ test_expect_success SYMLINKS 'checkout -f must not follow symlinks when removing
 	test_path_is_file untracked/f
 '
 
+test_expect_success 'checkout --overwrite-ignore should succeed if only ignored files in the way' '
+	git checkout -b df_conflict &&
+	test_commit contents some_dir &&
+	git checkout start &&
+	mkdir some_dir &&
+	echo autogenerated information >some_dir/ignore &&
+	echo ignore >.git/info/exclude &&
+	git checkout --overwrite-ignore df_conflict &&
+	! test_path_is_dir some_dir
+'
+
 test_done
diff --git a/unpack-trees.c b/unpack-trees.c
index 3d05e45a27..a37ab292bb 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -66,8 +66,8 @@ static const char *unpack_plumbing_errors[NB_UNPACK_TREES_WARNING_TYPES] = {
 };
 
 #define ERRORMSG(o,type) \
-	( ((o) && (o)->msgs[(type)]) \
-	  ? ((o)->msgs[(type)])      \
+	( ((o) && (o)->internal.msgs[(type)]) \
+	  ? ((o)->internal.msgs[(type)])      \
 	  : (unpack_plumbing_errors[(type)]) )
 
 static const char *super_prefixed(const char *path, const char *super_prefix)
@@ -108,10 +108,10 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 				  const char *cmd)
 {
 	int i;
-	const char **msgs = opts->msgs;
+	const char **msgs = opts->internal.msgs;
 	const char *msg;
 
-	strvec_init(&opts->msgs_to_free);
+	strvec_init(&opts->internal.msgs_to_free);
 
 	if (!strcmp(cmd, "checkout"))
 		msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
@@ -129,7 +129,7 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 			  "Please commit your changes or stash them before you %s.")
 		      : _("Your local changes to the following files would be overwritten by %s:\n%%s");
 	msgs[ERROR_WOULD_OVERWRITE] = msgs[ERROR_NOT_UPTODATE_FILE] =
-		strvec_pushf(&opts->msgs_to_free, msg, cmd, cmd);
+		strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);
 
 	msgs[ERROR_NOT_UPTODATE_DIR] =
 		_("Updating the following directories would lose untracked files in them:\n%s");
@@ -153,7 +153,7 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 			  "Please move or remove them before you %s.")
 		      : _("The following untracked working tree files would be removed by %s:\n%%s");
 	msgs[ERROR_WOULD_LOSE_UNTRACKED_REMOVED] =
-		strvec_pushf(&opts->msgs_to_free, msg, cmd, cmd);
+		strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);
 
 	if (!strcmp(cmd, "checkout"))
 		msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
@@ -171,7 +171,7 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 			  "Please move or remove them before you %s.")
 		      : _("The following untracked working tree files would be overwritten by %s:\n%%s");
 	msgs[ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN] =
-		strvec_pushf(&opts->msgs_to_free, msg, cmd, cmd);
+		strvec_pushf(&opts->internal.msgs_to_free, msg, cmd, cmd);
 
 	/*
 	 * Special case: ERROR_BIND_OVERLAP refers to a pair of paths, we
@@ -189,16 +189,16 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 	msgs[WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN] =
 		_("The following paths were already present and thus not updated despite sparse patterns:\n%s");
 
-	opts->show_all_errors = 1;
+	opts->internal.show_all_errors = 1;
 	/* rejected paths may not have a static buffer */
-	for (i = 0; i < ARRAY_SIZE(opts->unpack_rejects); i++)
-		opts->unpack_rejects[i].strdup_strings = 1;
+	for (i = 0; i < ARRAY_SIZE(opts->internal.unpack_rejects); i++)
+		opts->internal.unpack_rejects[i].strdup_strings = 1;
 }
 
 void clear_unpack_trees_porcelain(struct unpack_trees_options *opts)
 {
-	strvec_clear(&opts->msgs_to_free);
-	memset(opts->msgs, 0, sizeof(opts->msgs));
+	strvec_clear(&opts->internal.msgs_to_free);
+	memset(opts->internal.msgs, 0, sizeof(opts->internal.msgs));
 }
 
 static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
@@ -210,7 +210,7 @@ static int do_add_entry(struct unpack_trees_options *o, struct cache_entry *ce,
 		set |= CE_WT_REMOVE;
 
 	ce->ce_flags = (ce->ce_flags & ~clear) | set;
-	return add_index_entry(&o->result, ce,
+	return add_index_entry(&o->internal.result, ce,
 			       ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE);
 }
 
@@ -218,7 +218,7 @@ static void add_entry(struct unpack_trees_options *o,
 		      const struct cache_entry *ce,
 		      unsigned int set, unsigned int clear)
 {
-	do_add_entry(o, dup_cache_entry(ce, &o->result), set, clear);
+	do_add_entry(o, dup_cache_entry(ce, &o->internal.result), set, clear);
 }
 
 /*
@@ -233,7 +233,7 @@ static int add_rejected_path(struct unpack_trees_options *o,
 	if (o->quiet)
 		return -1;
 
-	if (!o->show_all_errors)
+	if (!o->internal.show_all_errors)
 		return error(ERRORMSG(o, e), super_prefixed(path,
 							    o->super_prefix));
 
@@ -241,7 +241,7 @@ static int add_rejected_path(struct unpack_trees_options *o,
 	 * Otherwise, insert in a list for future display by
 	 * display_(error|warning)_msgs()
 	 */
-	string_list_append(&o->unpack_rejects[e], path);
+	string_list_append(&o->internal.unpack_rejects[e], path);
 	return -1;
 }
 
@@ -253,7 +253,7 @@ static void display_error_msgs(struct unpack_trees_options *o)
 	int e;
 	unsigned error_displayed = 0;
 	for (e = 0; e < NB_UNPACK_TREES_ERROR_TYPES; e++) {
-		struct string_list *rejects = &o->unpack_rejects[e];
+		struct string_list *rejects = &o->internal.unpack_rejects[e];
 
 		if (rejects->nr > 0) {
 			int i;
@@ -281,7 +281,7 @@ static void display_warning_msgs(struct unpack_trees_options *o)
 	unsigned warning_displayed = 0;
 	for (e = NB_UNPACK_TREES_ERROR_TYPES + 1;
 	     e < NB_UNPACK_TREES_WARNING_TYPES; e++) {
-		struct string_list *rejects = &o->unpack_rejects[e];
+		struct string_list *rejects = &o->internal.unpack_rejects[e];
 
 		if (rejects->nr > 0) {
 			int i;
@@ -600,13 +600,14 @@ static void mark_ce_used(struct cache_entry *ce, struct unpack_trees_options *o)
 {
 	ce->ce_flags |= CE_UNPACKED;
 
-	if (o->cache_bottom < o->src_index->cache_nr &&
-	    o->src_index->cache[o->cache_bottom] == ce) {
-		int bottom = o->cache_bottom;
+	if (o->internal.cache_bottom < o->src_index->cache_nr &&
+	    o->src_index->cache[o->internal.cache_bottom] == ce) {
+		int bottom = o->internal.cache_bottom;
+
 		while (bottom < o->src_index->cache_nr &&
 		       o->src_index->cache[bottom]->ce_flags & CE_UNPACKED)
 			bottom++;
-		o->cache_bottom = bottom;
+		o->internal.cache_bottom = bottom;
 	}
 }
 
@@ -652,7 +653,7 @@ static void mark_ce_used_same_name(struct cache_entry *ce,
 static struct cache_entry *next_cache_entry(struct unpack_trees_options *o)
 {
 	const struct index_state *index = o->src_index;
-	int pos = o->cache_bottom;
+	int pos = o->internal.cache_bottom;
 
 	while (pos < index->cache_nr) {
 		struct cache_entry *ce = index->cache[pos];
@@ -711,7 +712,7 @@ static void restore_cache_bottom(struct traverse_info *info, int bottom)
 
 	if (o->diff_index_cached)
 		return;
-	o->cache_bottom = bottom;
+	o->internal.cache_bottom = bottom;
 }
 
 static int switch_cache_bottom(struct traverse_info *info)
@@ -721,13 +722,13 @@ static int switch_cache_bottom(struct traverse_info *info)
 
 	if (o->diff_index_cached)
 		return 0;
-	ret = o->cache_bottom;
+	ret = o->internal.cache_bottom;
 	pos = find_cache_pos(info->prev, info->name, info->namelen);
 
 	if (pos < -1)
-		o->cache_bottom = -2 - pos;
+		o->internal.cache_bottom = -2 - pos;
 	else if (pos < 0)
-		o->cache_bottom = o->src_index->cache_nr;
+		o->internal.cache_bottom = o->src_index->cache_nr;
 	return ret;
 }
 
@@ -838,7 +839,7 @@ static int traverse_by_cache_tree(int pos, int nr_entries, int nr_names,
 		mark_ce_used(src[0], o);
 	}
 	free(tree_ce);
-	if (o->debug_unpack)
+	if (o->internal.debug_unpack)
 		printf("Unpacked %d entries from %s to %s using cache-tree\n",
 		       nr_entries,
 		       o->src_index->cache[pos]->name,
@@ -873,9 +874,9 @@ static int traverse_trees_recursive(int n, unsigned long dirmask,
 		 * save and restore cache_bottom anyway to not miss
 		 * unprocessed entries before 'pos'.
 		 */
-		bottom = o->cache_bottom;
+		bottom = o->internal.cache_bottom;
 		ret = traverse_by_cache_tree(pos, nr_entries, n, info);
-		o->cache_bottom = bottom;
+		o->internal.cache_bottom = bottom;
 		return ret;
 	}
 
@@ -1212,8 +1213,8 @@ static int unpack_single_entry(int n, unsigned long mask,
 		 * cache entry from the index aware logic.
 		 */
 		src[i + o->merge] = create_ce_entry(info, names + i, stage,
-						    &o->result, o->merge,
-						    bit & dirmask);
+						    &o->internal.result,
+						    o->merge, bit & dirmask);
 	}
 
 	if (o->merge) {
@@ -1237,7 +1238,7 @@ static int unpack_single_entry(int n, unsigned long mask,
 
 static int unpack_failed(struct unpack_trees_options *o, const char *message)
 {
-	discard_index(&o->result);
+	discard_index(&o->internal.result);
 	if (!o->quiet && !o->exiting_early) {
 		if (message)
 			return error("%s", message);
@@ -1260,7 +1261,7 @@ static int find_cache_pos(struct traverse_info *info,
 	struct index_state *index = o->src_index;
 	int pfxlen = info->pathlen;
 
-	for (pos = o->cache_bottom; pos < index->cache_nr; pos++) {
+	for (pos = o->internal.cache_bottom; pos < index->cache_nr; pos++) {
 		const struct cache_entry *ce = index->cache[pos];
 		const char *ce_name, *ce_slash;
 		int cmp, ce_len;
@@ -1271,8 +1272,8 @@ static int find_cache_pos(struct traverse_info *info,
 			 * we can never match it; don't check it
 			 * again.
 			 */
-			if (pos == o->cache_bottom)
-				++o->cache_bottom;
+			if (pos == o->internal.cache_bottom)
+				++o->internal.cache_bottom;
 			continue;
 		}
 		if (!ce_in_traverse_path(ce, info)) {
@@ -1450,7 +1451,7 @@ static int unpack_sparse_callback(int n, unsigned long mask, unsigned long dirma
 	 */
 	if (!is_null_oid(&names[0].oid)) {
 		src[0] = create_ce_entry(info, &names[0], 0,
-					&o->result, 1,
+					&o->internal.result, 1,
 					dirmask & (1ul << 0));
 		src[0]->ce_flags |= (CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE);
 	}
@@ -1487,7 +1488,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 	while (!p->mode)
 		p++;
 
-	if (o->debug_unpack)
+	if (o->internal.debug_unpack)
 		debug_unpack_callback(n, mask, dirmask, names, info);
 
 	/* Are we supposed to look at the index too? */
@@ -1560,7 +1561,7 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
 				 * in 'mark_ce_used()'
 				 */
 				if (!src[0] || !S_ISSPARSEDIR(src[0]->ce_mode))
-					o->cache_bottom += matches;
+					o->internal.cache_bottom += matches;
 				return mask;
 			}
 		}
@@ -1809,7 +1810,7 @@ static void populate_from_existing_patterns(struct unpack_trees_options *o,
 	if (get_sparse_checkout_patterns(pl) < 0)
 		o->skip_sparse_checkout = 1;
 	else
-		o->pl = pl;
+		o->internal.pl = pl;
 }
 
 static void update_sparsity_for_prefix(const char *prefix,
@@ -1871,8 +1872,12 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 
 	if (len > MAX_UNPACK_TREES)
 		die("unpack_trees takes at most %d trees", MAX_UNPACK_TREES);
-	if (o->dir)
-		BUG("o->dir is for internal use only");
+	if (o->internal.dir)
+		BUG("o->internal.dir is for internal use only");
+	if (o->internal.pl)
+		BUG("o->internal.pl is for internal use only");
+	if (o->df_conflict_entry)
+		BUG("o->df_conflict_entry is an output only field");
 
 	trace_performance_enter();
 	trace2_region_enter("unpack_trees", "unpack_trees", the_repository);
@@ -1889,9 +1894,9 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 		BUG("UNPACK_RESET_OVERWRITE_UNTRACKED incompatible with preserved ignored files");
 
 	if (!o->preserve_ignored) {
-		o->dir = &dir;
-		o->dir->flags |= DIR_SHOW_IGNORED;
-		setup_standard_excludes(o->dir);
+		o->internal.dir = &dir;
+		o->internal.dir->flags |= DIR_SHOW_IGNORED;
+		setup_standard_excludes(o->internal.dir);
 	}
 
 	if (o->prefix)
@@ -1899,49 +1904,50 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 
 	if (!core_apply_sparse_checkout || !o->update)
 		o->skip_sparse_checkout = 1;
-	if (!o->skip_sparse_checkout && !o->pl) {
+	if (!o->skip_sparse_checkout) {
 		memset(&pl, 0, sizeof(pl));
 		free_pattern_list = 1;
 		populate_from_existing_patterns(o, &pl);
 	}
 
-	index_state_init(&o->result, o->src_index->repo);
-	o->result.initialized = 1;
-	o->result.timestamp.sec = o->src_index->timestamp.sec;
-	o->result.timestamp.nsec = o->src_index->timestamp.nsec;
-	o->result.version = o->src_index->version;
+	index_state_init(&o->internal.result, o->src_index->repo);
+	o->internal.result.initialized = 1;
+	o->internal.result.timestamp.sec = o->src_index->timestamp.sec;
+	o->internal.result.timestamp.nsec = o->src_index->timestamp.nsec;
+	o->internal.result.version = o->src_index->version;
 	if (!o->src_index->split_index) {
-		o->result.split_index = NULL;
+		o->internal.result.split_index = NULL;
 	} else if (o->src_index == o->dst_index) {
 		/*
 		 * o->dst_index (and thus o->src_index) will be discarded
-		 * and overwritten with o->result at the end of this function,
-		 * so just use src_index's split_index to avoid having to
-		 * create a new one.
+		 * and overwritten with o->internal.result at the end of
+		 * this function, so just use src_index's split_index to
+		 * avoid having to create a new one.
 		 */
-		o->result.split_index = o->src_index->split_index;
-		o->result.split_index->refcount++;
+		o->internal.result.split_index = o->src_index->split_index;
+		o->internal.result.split_index->refcount++;
 	} else {
-		o->result.split_index = init_split_index(&o->result);
+		o->internal.result.split_index =
+			init_split_index(&o->internal.result);
 	}
-	oidcpy(&o->result.oid, &o->src_index->oid);
-	o->merge_size = len;
+	oidcpy(&o->internal.result.oid, &o->src_index->oid);
+	o->internal.merge_size = len;
 	mark_all_ce_unused(o->src_index);
 
-	o->result.fsmonitor_last_update =
+	o->internal.result.fsmonitor_last_update =
 		xstrdup_or_null(o->src_index->fsmonitor_last_update);
-	o->result.fsmonitor_has_run_once = o->src_index->fsmonitor_has_run_once;
+	o->internal.result.fsmonitor_has_run_once = o->src_index->fsmonitor_has_run_once;
 
 	if (!o->src_index->initialized &&
 	    !repo->settings.command_requires_full_index &&
-	    is_sparse_index_allowed(&o->result, 0))
-		o->result.sparse_index = 1;
+	    is_sparse_index_allowed(&o->internal.result, 0))
+		o->internal.result.sparse_index = 1;
 
 	/*
 	 * Sparse checkout loop #1: set NEW_SKIP_WORKTREE on existing entries
 	 */
 	if (!o->skip_sparse_checkout)
-		mark_new_skip_worktree(o->pl, o->src_index, 0,
+		mark_new_skip_worktree(o->internal.pl, o->src_index, 0,
 				       CE_NEW_SKIP_WORKTREE, o->verbose_update);
 
 	if (!dfc)
@@ -1955,7 +1961,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 		setup_traverse_info(&info, prefix);
 		info.fn = unpack_callback;
 		info.data = o;
-		info.show_all_errors = o->show_all_errors;
+		info.show_all_errors = o->internal.show_all_errors;
 		info.pathspec = o->pathspec;
 
 		if (o->prefix) {
@@ -1996,7 +2002,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	}
 	mark_all_ce_unused(o->src_index);
 
-	if (o->trivial_merges_only && o->nontrivial_merge) {
+	if (o->trivial_merges_only && o->internal.nontrivial_merge) {
 		ret = unpack_failed(o, "Merge requires file-level merging");
 		goto done;
 	}
@@ -2007,13 +2013,13 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 		 * If they will have NEW_SKIP_WORKTREE, also set CE_SKIP_WORKTREE
 		 * so apply_sparse_checkout() won't attempt to remove it from worktree
 		 */
-		mark_new_skip_worktree(o->pl, &o->result,
+		mark_new_skip_worktree(o->internal.pl, &o->internal.result,
 				       CE_ADDED, CE_SKIP_WORKTREE | CE_NEW_SKIP_WORKTREE,
 				       o->verbose_update);
 
 		ret = 0;
-		for (i = 0; i < o->result.cache_nr; i++) {
-			struct cache_entry *ce = o->result.cache[i];
+		for (i = 0; i < o->internal.result.cache_nr; i++) {
+			struct cache_entry *ce = o->internal.result.cache[i];
 
 			/*
 			 * Entries marked with CE_ADDED in merged_entry() do not have
@@ -2027,7 +2033,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 			    verify_absent(ce, WARNING_SPARSE_ORPHANED_NOT_OVERWRITTEN, o))
 				ret = 1;
 
-			if (apply_sparse_checkout(&o->result, ce, o))
+			if (apply_sparse_checkout(&o->internal.result, ce, o))
 				ret = 1;
 		}
 		if (ret == 1) {
@@ -2035,46 +2041,47 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 			 * Inability to sparsify or de-sparsify individual
 			 * paths is not an error, but just a warning.
 			 */
-			if (o->show_all_errors)
+			if (o->internal.show_all_errors)
 				display_warning_msgs(o);
 			ret = 0;
 		}
 	}
 
-	ret = check_updates(o, &o->result) ? (-2) : 0;
+	ret = check_updates(o, &o->internal.result) ? (-2) : 0;
 	if (o->dst_index) {
-		move_index_extensions(&o->result, o->src_index);
+		move_index_extensions(&o->internal.result, o->src_index);
 		if (!ret) {
 			if (git_env_bool("GIT_TEST_CHECK_CACHE_TREE", 0))
-				cache_tree_verify(the_repository, &o->result);
+				cache_tree_verify(the_repository,
+						  &o->internal.result);
 			if (!o->skip_cache_tree_update &&
-			    !cache_tree_fully_valid(o->result.cache_tree))
-				cache_tree_update(&o->result,
+			    !cache_tree_fully_valid(o->internal.result.cache_tree))
+				cache_tree_update(&o->internal.result,
 						  WRITE_TREE_SILENT |
 						  WRITE_TREE_REPAIR);
 		}
 
-		o->result.updated_workdir = 1;
+		o->internal.result.updated_workdir = 1;
 		discard_index(o->dst_index);
-		*o->dst_index = o->result;
+		*o->dst_index = o->internal.result;
 	} else {
-		discard_index(&o->result);
+		discard_index(&o->internal.result);
 	}
 	o->src_index = NULL;
 
 done:
 	if (free_pattern_list)
 		clear_pattern_list(&pl);
-	if (o->dir) {
-		dir_clear(o->dir);
-		o->dir = NULL;
+	if (o->internal.dir) {
+		dir_clear(o->internal.dir);
+		o->internal.dir = NULL;
 	}
 	trace2_region_leave("unpack_trees", "unpack_trees", the_repository);
 	trace_performance_leave("unpack_trees");
 	return ret;
 
 return_failed:
-	if (o->show_all_errors)
+	if (o->internal.show_all_errors)
 		display_error_msgs(o);
 	mark_all_ce_unused(o->src_index);
 	ret = unpack_failed(o, NULL);
@@ -2089,16 +2096,17 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
  *
  * CE_NEW_SKIP_WORKTREE is used internally.
  */
-enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
+enum update_sparsity_result update_sparsity(struct unpack_trees_options *o,
+					    struct pattern_list *pl)
 {
 	enum update_sparsity_result ret = UPDATE_SPARSITY_SUCCESS;
-	struct pattern_list pl;
 	int i;
 	unsigned old_show_all_errors;
 	int free_pattern_list = 0;
 
-	old_show_all_errors = o->show_all_errors;
-	o->show_all_errors = 1;
+	old_show_all_errors = o->internal.show_all_errors;
+	o->internal.show_all_errors = 1;
+	index_state_init(&o->internal.result, o->src_index->repo);
 
 	/* Sanity checks */
 	if (!o->update || o->index_only || o->skip_sparse_checkout)
@@ -2109,20 +2117,19 @@ enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
 	trace_performance_enter();
 
 	/* If we weren't given patterns, use the recorded ones */
-	if (!o->pl) {
-		memset(&pl, 0, sizeof(pl));
+	if (!pl) {
 		free_pattern_list = 1;
-		populate_from_existing_patterns(o, &pl);
-		if (o->skip_sparse_checkout)
-			goto skip_sparse_checkout;
+		pl = xcalloc(1, sizeof(*pl));
+		populate_from_existing_patterns(o, pl);
 	}
+	o->internal.pl = pl;
 
 	/* Expand sparse directories as needed */
-	expand_index(o->src_index, o->pl);
+	expand_index(o->src_index, o->internal.pl);
 
 	/* Set NEW_SKIP_WORKTREE on existing entries. */
 	mark_all_ce_unused(o->src_index);
-	mark_new_skip_worktree(o->pl, o->src_index, 0,
+	mark_new_skip_worktree(o->internal.pl, o->src_index, 0,
 			       CE_NEW_SKIP_WORKTREE, o->verbose_update);
 
 	/* Then loop over entries and update/remove as needed */
@@ -2142,14 +2149,16 @@ enum update_sparsity_result update_sparsity(struct unpack_trees_options *o)
 			ret = UPDATE_SPARSITY_WARNINGS;
 	}
 
-skip_sparse_checkout:
 	if (check_updates(o, o->src_index))
 		ret = UPDATE_SPARSITY_WORKTREE_UPDATE_FAILURES;
 
 	display_warning_msgs(o);
-	o->show_all_errors = old_show_all_errors;
-	if (free_pattern_list)
-		clear_pattern_list(&pl);
+	o->internal.show_all_errors = old_show_all_errors;
+	if (free_pattern_list) {
+		clear_pattern_list(pl);
+		free(pl);
+		o->internal.pl = NULL;
+	}
 	trace_performance_leave("update_sparsity");
 	return ret;
 }
@@ -2244,15 +2253,15 @@ static int verify_uptodate_sparse(const struct cache_entry *ce,
 }
 
 /*
- * TODO: We should actually invalidate o->result, not src_index [1].
+ * TODO: We should actually invalidate o->internal.result, not src_index [1].
  * But since cache tree and untracked cache both are not copied to
- * o->result until unpacking is complete, we invalidate them on
+ * o->internal.result until unpacking is complete, we invalidate them on
  * src_index instead with the assumption that they will be copied to
  * dst_index at the end.
  *
  * [1] src_index->cache_tree is also used in unpack_callback() so if
- * we invalidate o->result, we need to update it to use
- * o->result.cache_tree as well.
+ * we invalidate o->internal.result, we need to update it to use
+ * o->internal.result.cache_tree as well.
  */
 static void invalidate_ce_path(const struct cache_entry *ce,
 			       struct unpack_trees_options *o)
@@ -2336,8 +2345,8 @@ static int verify_clean_subdirectory(const struct cache_entry *ce,
 	pathbuf = xstrfmt("%.*s/", namelen, ce->name);
 
 	memset(&d, 0, sizeof(d));
-	if (o->dir)
-		d.exclude_per_dir = o->dir->exclude_per_dir;
+	if (o->internal.dir)
+		setup_standard_excludes(&d);
 	i = read_directory(&d, o->src_index, pathbuf, namelen+1, NULL);
 	dir_clear(&d);
 	free(pathbuf);
@@ -2391,8 +2400,8 @@ static int check_ok_to_remove(const char *name, int len, int dtype,
 	if (ignore_case && icase_exists(o, name, len, st))
 		return 0;
 
-	if (o->dir &&
-	    is_excluded(o->dir, o->src_index, name, &dtype))
+	if (o->internal.dir &&
+	    is_excluded(o->internal.dir, o->src_index, name, &dtype))
 		/*
 		 * ce->name is explicitly excluded, so it is Ok to
 		 * overwrite it.
@@ -2420,7 +2429,7 @@ static int check_ok_to_remove(const char *name, int len, int dtype,
 	 * delete this path, which is in a subdirectory that
 	 * is being replaced with a blob.
 	 */
-	result = index_file_exists(&o->result, name, len, 0);
+	result = index_file_exists(&o->internal.result, name, len, 0);
 	if (result) {
 		if (result->ce_flags & CE_REMOVE)
 			return 0;
@@ -2521,7 +2530,7 @@ static int merged_entry(const struct cache_entry *ce,
 			struct unpack_trees_options *o)
 {
 	int update = CE_UPDATE;
-	struct cache_entry *merge = dup_cache_entry(ce, &o->result);
+	struct cache_entry *merge = dup_cache_entry(ce, &o->internal.result);
 
 	if (!old) {
 		/*
@@ -2616,7 +2625,7 @@ static int merged_sparse_dir(const struct cache_entry * const *src, int n,
 	setup_traverse_info(&info, src[0]->name);
 	info.fn = unpack_sparse_callback;
 	info.data = o;
-	info.show_all_errors = o->show_all_errors;
+	info.show_all_errors = o->internal.show_all_errors;
 	info.pathspec = o->pathspec;
 
 	/* Get the tree descriptors of the sparse directory in each of the merging trees */
@@ -2834,7 +2843,7 @@ int threeway_merge(const struct cache_entry * const *stages,
 			return -1;
 	}
 
-	o->nontrivial_merge = 1;
+	o->internal.nontrivial_merge = 1;
 
 	/* #2, #3, #4, #6, #7, #9, #10, #11. */
 	count = 0;
@@ -2875,9 +2884,9 @@ int twoway_merge(const struct cache_entry * const *src,
 	const struct cache_entry *oldtree = src[1];
 	const struct cache_entry *newtree = src[2];
 
-	if (o->merge_size != 2)
+	if (o->internal.merge_size != 2)
 		return error("Cannot do a twoway merge of %d trees",
-			     o->merge_size);
+			     o->internal.merge_size);
 
 	if (oldtree == o->df_conflict_entry)
 		oldtree = NULL;
@@ -2957,9 +2966,9 @@ int bind_merge(const struct cache_entry * const *src,
 	const struct cache_entry *old = src[0];
 	const struct cache_entry *a = src[1];
 
-	if (o->merge_size != 1)
+	if (o->internal.merge_size != 1)
 		return error("Cannot do a bind merge of %d trees",
-			     o->merge_size);
+			     o->internal.merge_size);
 	if (a && old)
 		return o->quiet ? -1 :
 			error(ERRORMSG(o, ERROR_BIND_OVERLAP),
@@ -2983,9 +2992,9 @@ int oneway_merge(const struct cache_entry * const *src,
 	const struct cache_entry *old = src[0];
 	const struct cache_entry *a = src[1];
 
-	if (o->merge_size != 1)
+	if (o->internal.merge_size != 1)
 		return error("Cannot do a oneway merge of %d trees",
-			     o->merge_size);
+			     o->internal.merge_size);
 
 	if (!a || a == o->df_conflict_entry)
 		return deleted_entry(old, old, o);
@@ -3020,8 +3029,8 @@ int stash_worktree_untracked_merge(const struct cache_entry * const *src,
 	const struct cache_entry *worktree = src[1];
 	const struct cache_entry *untracked = src[2];
 
-	if (o->merge_size != 2)
-		BUG("invalid merge_size: %d", o->merge_size);
+	if (o->internal.merge_size != 2)
+		BUG("invalid merge_size: %d", o->internal.merge_size);
 
 	if (worktree && untracked)
 		return error(_("worktree and untracked commit have duplicate entries: %s"),
diff --git a/unpack-trees.h b/unpack-trees.h
index 3a7b3e5f00..61c06eb7c5 100644
--- a/unpack-trees.h
+++ b/unpack-trees.h
@@ -59,47 +59,54 @@ struct unpack_trees_options {
 		     preserve_ignored,
 		     clone,
 		     index_only,
-		     nontrivial_merge,
 		     trivial_merges_only,
 		     verbose_update,
 		     aggressive,
 		     skip_unmerged,
 		     initial_checkout,
 		     diff_index_cached,
-		     debug_unpack,
 		     skip_sparse_checkout,
 		     quiet,
 		     exiting_early,
-		     show_all_errors,
 		     dry_run,
 		     skip_cache_tree_update;
 	enum unpack_trees_reset_type reset;
 	const char *prefix;
 	const char *super_prefix;
-	int cache_bottom;
 	struct pathspec *pathspec;
 	merge_fn_t fn;
-	const char *msgs[NB_UNPACK_TREES_WARNING_TYPES];
-	struct strvec msgs_to_free;
-	/*
-	 * Store error messages in an array, each case
-	 * corresponding to a error message type
-	 */
-	struct string_list unpack_rejects[NB_UNPACK_TREES_WARNING_TYPES];
 
 	int head_idx;
-	int merge_size;
 
-	struct cache_entry *df_conflict_entry;
+	struct cache_entry *df_conflict_entry; /* output only */
 	void *unpack_data;
 
 	struct index_state *dst_index;
 	struct index_state *src_index;
-	struct index_state result;
 
-	struct pattern_list *pl; /* for internal use */
-	struct dir_struct *dir; /* for internal use only */
 	struct checkout_metadata meta;
+
+	struct unpack_trees_options_internal {
+		unsigned int nontrivial_merge,
+			     show_all_errors,
+			     debug_unpack; /* used by read-tree debugging */
+
+		int merge_size; /* used by read-tree debugging */
+		int cache_bottom;
+		const char *msgs[NB_UNPACK_TREES_WARNING_TYPES];
+		struct strvec msgs_to_free;
+
+		/*
+		 * Store error messages in an array, each case
+		 * corresponding to a error message type
+		 */
+		struct string_list unpack_rejects[NB_UNPACK_TREES_WARNING_TYPES];
+
+		struct index_state result;
+
+		struct pattern_list *pl;
+		struct dir_struct *dir;
+	} internal;
 };
 
 int unpack_trees(unsigned n, struct tree_desc *t,
@@ -112,7 +119,8 @@ enum update_sparsity_result {
 	UPDATE_SPARSITY_WORKTREE_UPDATE_FAILURES = -2
 };
 
-enum update_sparsity_result update_sparsity(struct unpack_trees_options *options);
+enum update_sparsity_result update_sparsity(struct unpack_trees_options *options,
+					    struct pattern_list *pl);
 
 int verify_uptodate(const struct cache_entry *ce,
 		    struct unpack_trees_options *o);