diff --git a/builtin.h b/builtin.h
index 46cc789789..cb0db67681 100644
--- a/builtin.h
+++ b/builtin.h
@@ -107,6 +107,16 @@ void setup_auto_pager(const char *cmd, int def);
 
 int is_builtin(const char *s);
 
+/*
+ * Builtins which do not use RUN_SETUP should never see
+ * a prefix that is not empty; use this to protect downstream
+ * code which is not prepared to call prefix_filename(), etc.
+ */
+#define BUG_ON_NON_EMPTY_PREFIX(prefix) do { \
+	if ((prefix)) \
+		BUG("unexpected prefix in builtin: %s", (prefix)); \
+} while (0)
+
 int cmd_add(int argc, const char **argv, const char *prefix);
 int cmd_am(int argc, const char **argv, const char *prefix);
 int cmd_annotate(int argc, const char **argv, const char *prefix);
diff --git a/builtin/check-ref-format.c b/builtin/check-ref-format.c
index fd0e5f8683..462eefe102 100644
--- a/builtin/check-ref-format.c
+++ b/builtin/check-ref-format.c
@@ -60,6 +60,8 @@ int cmd_check_ref_format(int argc, const char **argv, const char *prefix)
 	char *to_free = NULL;
 	int ret = 1;
 
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(builtin_check_ref_format_usage);
 
diff --git a/builtin/credential.c b/builtin/credential.c
index d7b304fa08..7010752987 100644
--- a/builtin/credential.c
+++ b/builtin/credential.c
@@ -6,7 +6,7 @@
 static const char usage_msg[] =
 	"git credential (fill|approve|reject)";
 
-int cmd_credential(int argc, const char **argv, const char *prefix)
+int cmd_credential(int argc, const char **argv, const char *prefix UNUSED)
 {
 	const char *op;
 	struct credential c = CREDENTIAL_INIT;
diff --git a/builtin/diff.c b/builtin/diff.c
index 26f1e532c6..bc9da7bcb6 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -74,7 +74,7 @@ static void stuff_change(struct diff_options *opt,
 }
 
 static int builtin_diff_b_f(struct rev_info *revs,
-			    int argc, const char **argv,
+			    int argc, const char **argv UNUSED,
 			    struct object_array_entry **blob)
 {
 	/* Blob vs file in the working tree*/
@@ -109,7 +109,7 @@ static int builtin_diff_b_f(struct rev_info *revs,
 }
 
 static int builtin_diff_blobs(struct rev_info *revs,
-			      int argc, const char **argv,
+			      int argc, const char **argv UNUSED,
 			      struct object_array_entry **blob)
 {
 	const unsigned mode = canon_mode(S_IFREG | 0644);
@@ -209,7 +209,7 @@ static int builtin_diff_tree(struct rev_info *revs,
 }
 
 static int builtin_diff_combined(struct rev_info *revs,
-				 int argc, const char **argv,
+				 int argc, const char **argv UNUSED,
 				 struct object_array_entry *ent,
 				 int ents, int first_non_parent)
 {
diff --git a/builtin/fast-import.c b/builtin/fast-import.c
index f7548ff4a3..19427e05f1 100644
--- a/builtin/fast-import.c
+++ b/builtin/fast-import.c
@@ -176,6 +176,7 @@ static FILE *pack_edges;
 static unsigned int show_stats = 1;
 static int global_argc;
 static const char **global_argv;
+static const char *global_prefix;
 
 /* Memory pools */
 static struct mem_pool fi_mem_pool = {
@@ -3246,7 +3247,7 @@ static void parse_alias(void)
 static char* make_fast_import_path(const char *path)
 {
 	if (!relative_marks_paths || is_absolute_path(path))
-		return xstrdup(path);
+		return prefix_filename(global_prefix, path);
 	return git_pathdup("info/fast-import/%s", path);
 }
 
@@ -3317,9 +3318,11 @@ static void option_cat_blob_fd(const char *fd)
 
 static void option_export_pack_edges(const char *edges)
 {
+	char *fn = prefix_filename(global_prefix, edges);
 	if (pack_edges)
 		fclose(pack_edges);
-	pack_edges = xfopen(edges, "a");
+	pack_edges = xfopen(fn, "a");
+	free(fn);
 }
 
 static void option_rewrite_submodules(const char *arg, struct string_list *list)
@@ -3334,11 +3337,13 @@ static void option_rewrite_submodules(const char *arg, struct string_list *list)
 	f++;
 	CALLOC_ARRAY(ms, 1);
 
+	f = prefix_filename(global_prefix, f);
 	fp = fopen(f, "r");
 	if (!fp)
 		die_errno("cannot read '%s'", f);
 	read_mark_file(&ms, fp, insert_oid_entry);
 	fclose(fp);
+	free(f);
 
 	string_list_insert(list, s)->util = ms;
 }
@@ -3552,6 +3557,7 @@ int cmd_fast_import(int argc, const char **argv, const char *prefix)
 
 	global_argc = argc;
 	global_argv = argv;
+	global_prefix = prefix;
 
 	rc_free = mem_pool_alloc(&fi_mem_pool, cmd_save * sizeof(*rc_free));
 	for (i = 0; i < (cmd_save - 1); i++)
diff --git a/builtin/fetch-pack.c b/builtin/fetch-pack.c
index d1a4306da3..0d75e474f0 100644
--- a/builtin/fetch-pack.c
+++ b/builtin/fetch-pack.c
@@ -42,7 +42,7 @@ static void add_sought_entry(struct ref ***sought, int *nr, int *alloc,
 	(*sought)[*nr - 1] = ref;
 }
 
-int cmd_fetch_pack(int argc, const char **argv, const char *prefix)
+int cmd_fetch_pack(int argc, const char **argv, const char *prefix UNUSED)
 {
 	int i, ret;
 	struct ref *ref = NULL;
diff --git a/builtin/fsmonitor--daemon.c b/builtin/fsmonitor--daemon.c
index cae804a190..3d4f2ae1d0 100644
--- a/builtin/fsmonitor--daemon.c
+++ b/builtin/fsmonitor--daemon.c
@@ -1575,7 +1575,7 @@ int cmd_fsmonitor__daemon(int argc, const char **argv, const char *prefix)
 }
 
 #else
-int cmd_fsmonitor__daemon(int argc, const char **argv, const char *prefix)
+int cmd_fsmonitor__daemon(int argc, const char **argv, const char *prefix UNUSED)
 {
 	struct option options[] = {
 		OPT_END()
diff --git a/builtin/get-tar-commit-id.c b/builtin/get-tar-commit-id.c
index 491af9202d..4324d39fb4 100644
--- a/builtin/get-tar-commit-id.c
+++ b/builtin/get-tar-commit-id.c
@@ -14,7 +14,7 @@ static const char builtin_get_tar_commit_id_usage[] =
 #define RECORDSIZE	(512)
 #define HEADERSIZE (2 * RECORDSIZE)
 
-int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
+int cmd_get_tar_commit_id(int argc, const char **argv UNUSED, const char *prefix)
 {
 	char buffer[HEADERSIZE];
 	struct ustar_header *header = (struct ustar_header *)buffer;
@@ -24,6 +24,8 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
 	long len;
 	char *end;
 
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	if (argc != 1)
 		usage(builtin_get_tar_commit_id_usage);
 
diff --git a/builtin/mailsplit.c b/builtin/mailsplit.c
index 73509f651b..91e93f0c77 100644
--- a/builtin/mailsplit.c
+++ b/builtin/mailsplit.c
@@ -277,6 +277,8 @@ int cmd_mailsplit(int argc, const char **argv, const char *prefix)
 	const char **argp;
 	static const char *stdin_only[] = { "-", NULL };
 
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	for (argp = argv+1; *argp; argp++) {
 		const char *arg = *argp;
 
diff --git a/builtin/merge-index.c b/builtin/merge-index.c
index c875f5d37e..b747b4ed98 100644
--- a/builtin/merge-index.c
+++ b/builtin/merge-index.c
@@ -71,7 +71,7 @@ static void merge_all(void)
 	}
 }
 
-int cmd_merge_index(int argc, const char **argv, const char *prefix)
+int cmd_merge_index(int argc, const char **argv, const char *prefix UNUSED)
 {
 	int i, force_file = 0;
 
diff --git a/builtin/merge-ours.c b/builtin/merge-ours.c
index 284eb48609..c2e519301e 100644
--- a/builtin/merge-ours.c
+++ b/builtin/merge-ours.c
@@ -14,7 +14,7 @@
 static const char builtin_merge_ours_usage[] =
 	"git merge-ours <base>... -- HEAD <remote>...";
 
-int cmd_merge_ours(int argc, const char **argv, const char *prefix)
+int cmd_merge_ours(int argc, const char **argv, const char *prefix UNUSED)
 {
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(builtin_merge_ours_usage);
diff --git a/builtin/merge-recursive.c b/builtin/merge-recursive.c
index b9acbf5d34..0a50d0a0ae 100644
--- a/builtin/merge-recursive.c
+++ b/builtin/merge-recursive.c
@@ -20,7 +20,7 @@ static char *better_branch_name(const char *branch)
 	return xstrdup(name ? name : branch);
 }
 
-int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
+int cmd_merge_recursive(int argc, const char **argv, const char *prefix UNUSED)
 {
 	const struct object_id *bases[21];
 	unsigned bases_count = 0;
diff --git a/builtin/mktag.c b/builtin/mktag.c
index 42c2457c70..967a4442de 100644
--- a/builtin/mktag.c
+++ b/builtin/mktag.c
@@ -81,7 +81,7 @@ int cmd_mktag(int argc, const char **argv, const char *prefix)
 	int tagged_type;
 	struct object_id result;
 
-	argc = parse_options(argc, argv, NULL,
+	argc = parse_options(argc, argv, prefix,
 			     builtin_mktag_options,
 			     builtin_mktag_usage, 0);
 
diff --git a/builtin/pack-redundant.c b/builtin/pack-redundant.c
index 5e93d87320..d50c2d6693 100644
--- a/builtin/pack-redundant.c
+++ b/builtin/pack-redundant.c
@@ -558,7 +558,7 @@ static void load_all(void)
 	}
 }
 
-int cmd_pack_redundant(int argc, const char **argv, const char *prefix)
+int cmd_pack_redundant(int argc, const char **argv, const char *prefix UNUSED)
 {
 	int i;
 	int i_still_use_this = 0;
diff --git a/builtin/remote-ext.c b/builtin/remote-ext.c
index ee338bf440..282782eccd 100644
--- a/builtin/remote-ext.c
+++ b/builtin/remote-ext.c
@@ -197,6 +197,8 @@ static int command_loop(const char *child)
 
 int cmd_remote_ext(int argc, const char **argv, const char *prefix)
 {
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	if (argc != 3)
 		usage(usage_msg);
 
diff --git a/builtin/remote-fd.c b/builtin/remote-fd.c
index b2a3980b1d..9020fab9c5 100644
--- a/builtin/remote-fd.c
+++ b/builtin/remote-fd.c
@@ -59,6 +59,8 @@ int cmd_remote_fd(int argc, const char **argv, const char *prefix)
 	int output_fd = -1;
 	char *end;
 
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	if (argc != 3)
 		usage(usage_msg);
 
diff --git a/builtin/revert.c b/builtin/revert.c
index 62986a7b1b..287721fd37 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -94,7 +94,8 @@ static void verify_opt_compatible(const char *me, const char *base_opt, ...)
 		die(_("%s: %s cannot be used with %s"), me, this_opt, base_opt);
 }
 
-static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
+static int run_sequencer(int argc, const char **argv, const char *prefix,
+			 struct replay_opts *opts)
 {
 	const char * const * usage_str = revert_or_cherry_pick_usage(opts);
 	const char *me = action_name(opts);
@@ -141,7 +142,7 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 		options = parse_options_concat(options, cp_extra);
 	}
 
-	argc = parse_options(argc, argv, NULL, options, usage_str,
+	argc = parse_options(argc, argv, prefix, options, usage_str,
 			PARSE_OPT_KEEP_ARGV0 |
 			PARSE_OPT_KEEP_UNKNOWN_OPT);
 
@@ -246,7 +247,7 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
 
 	opts.action = REPLAY_REVERT;
 	sequencer_init_config(&opts);
-	res = run_sequencer(argc, argv, &opts);
+	res = run_sequencer(argc, argv, prefix, &opts);
 	if (res < 0)
 		die(_("revert failed"));
 	replay_opts_release(&opts);
@@ -260,7 +261,7 @@ int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 
 	opts.action = REPLAY_PICK;
 	sequencer_init_config(&opts);
-	res = run_sequencer(argc, argv, &opts);
+	res = run_sequencer(argc, argv, prefix, &opts);
 	if (res < 0)
 		die(_("cherry-pick failed"));
 	replay_opts_release(&opts);
diff --git a/builtin/stash.c b/builtin/stash.c
index 6a12fed271..5f327435b5 100644
--- a/builtin/stash.c
+++ b/builtin/stash.c
@@ -1466,7 +1466,7 @@ done:
 	return ret;
 }
 
-static int create_stash(int argc, const char **argv, const char *prefix)
+static int create_stash(int argc, const char **argv, const char *prefix UNUSED)
 {
 	int ret;
 	struct strbuf stash_msg_buf = STRBUF_INIT;
diff --git a/builtin/submodule--helper.c b/builtin/submodule--helper.c
index d05d1a8462..65a053261a 100644
--- a/builtin/submodule--helper.c
+++ b/builtin/submodule--helper.c
@@ -2766,7 +2766,7 @@ cleanup:
 	return ret;
 }
 
-static int push_check(int argc, const char **argv, const char *prefix)
+static int push_check(int argc, const char **argv, const char *prefix UNUSED)
 {
 	struct remote *remote;
 	const char *superproject_head;
diff --git a/builtin/unpack-file.c b/builtin/unpack-file.c
index e9b105a539..374d980c91 100644
--- a/builtin/unpack-file.c
+++ b/builtin/unpack-file.c
@@ -24,7 +24,7 @@ static char *create_temp_file(struct object_id *oid)
 	return path;
 }
 
-int cmd_unpack_file(int argc, const char **argv, const char *prefix)
+int cmd_unpack_file(int argc, const char **argv, const char *prefix UNUSED)
 {
 	struct object_id oid;
 
diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c
index 1908dcfcff..3d8510ccf8 100644
--- a/builtin/unpack-objects.c
+++ b/builtin/unpack-objects.c
@@ -600,7 +600,7 @@ static void unpack_all(void)
 		die("unresolved deltas left after unpacking");
 }
 
-int cmd_unpack_objects(int argc, const char **argv, const char *prefix)
+int cmd_unpack_objects(int argc, const char **argv, const char *prefix UNUSED)
 {
 	int i;
 	struct object_id oid;
diff --git a/builtin/upload-archive.c b/builtin/upload-archive.c
index 945ee2b412..7f9320ac6d 100644
--- a/builtin/upload-archive.c
+++ b/builtin/upload-archive.c
@@ -79,6 +79,8 @@ int cmd_upload_archive(int argc, const char **argv, const char *prefix)
 {
 	struct child_process writer = CHILD_PROCESS_INIT;
 
+	BUG_ON_NON_EMPTY_PREFIX(prefix);
+
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(upload_archive_usage);
 
diff --git a/builtin/var.c b/builtin/var.c
index d9943be9af..acb988d2d5 100644
--- a/builtin/var.c
+++ b/builtin/var.c
@@ -78,7 +78,7 @@ static int show_config(const char *var, const char *value, void *cb)
 	return git_default_config(var, value, cb);
 }
 
-int cmd_var(int argc, const char **argv, const char *prefix)
+int cmd_var(int argc, const char **argv, const char *prefix UNUSED)
 {
 	const struct git_var *git_var;
 	const char *val;
diff --git a/parse-options-cb.c b/parse-options-cb.c
index d346dbe210..4729277aa6 100644
--- a/parse-options-cb.c
+++ b/parse-options-cb.c
@@ -213,21 +213,6 @@ int parse_opt_noop_cb(const struct option *opt, const char *arg, int unset)
 	return 0;
 }
 
-/**
- * Report that the option is unknown, so that other code can handle
- * it. This can be used as a callback together with
- * OPTION_LOWLEVEL_CALLBACK to allow an option to be documented in the
- * "-h" output even if it's not being handled directly by
- * parse_options().
- */
-enum parse_opt_result parse_opt_unknown_cb(struct parse_opt_ctx_t *ctx,
-					   const struct option *opt,
-					   const char *arg, int unset)
-{
-	BUG_ON_OPT_ARG(arg);
-	return PARSE_OPT_UNKNOWN;
-}
-
 /**
  * Recreates the command-line option in the strbuf.
  */
diff --git a/parse-options.h b/parse-options.h
index 26f19384e5..fcb58c4043 100644
--- a/parse-options.h
+++ b/parse-options.h
@@ -479,9 +479,6 @@ int parse_opt_commit(const struct option *, const char *, int);
 int parse_opt_tertiary(const struct option *, const char *, int);
 int parse_opt_string_list(const struct option *, const char *, int);
 int parse_opt_noop_cb(const struct option *, const char *, int);
-enum parse_opt_result parse_opt_unknown_cb(struct parse_opt_ctx_t *ctx,
-					   const struct option *,
-					   const char *, int);
 int parse_opt_passthru(const struct option *, const char *, int);
 int parse_opt_passthru_argv(const struct option *, const char *, int);
 /* value is enum branch_track* */
diff --git a/scalar.c b/scalar.c
index ca19b95ce4..c7b8c16c8e 100644
--- a/scalar.c
+++ b/scalar.c
@@ -563,7 +563,7 @@ static int cmd_diagnose(int argc, const char **argv)
 	return res;
 }
 
-static int cmd_list(int argc, const char **argv)
+static int cmd_list(int argc, const char **argv UNUSED)
 {
 	if (argc != 1)
 		die(_("`scalar list` does not take arguments"));
diff --git a/t/helper/test-ctype.c b/t/helper/test-ctype.c
index 534ca66441..71a1a5c9b0 100644
--- a/t/helper/test-ctype.c
+++ b/t/helper/test-ctype.c
@@ -47,7 +47,7 @@ static int is_in(const char *s, int ch)
 	"\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f" \
 	"\x7f"
 
-int cmd__ctype(int argc, const char **argv)
+int cmd__ctype(int argc UNUSED, const char **argv UNUSED)
 {
 	TEST_CLASS(isdigit, DIGIT);
 	TEST_CLASS(isspace, " \n\r\t");
diff --git a/t/helper/test-date.c b/t/helper/test-date.c
index 45951b1df8..cd6a6df702 100644
--- a/t/helper/test-date.c
+++ b/t/helper/test-date.c
@@ -104,7 +104,7 @@ static void getnanos(const char **argv)
 	printf("%lf\n", seconds);
 }
 
-int cmd__date(int argc, const char **argv)
+int cmd__date(int argc UNUSED, const char **argv)
 {
 	const char *x;
 
diff --git a/t/helper/test-drop-caches.c b/t/helper/test-drop-caches.c
index e37396dd9c..73e551cfc2 100644
--- a/t/helper/test-drop-caches.c
+++ b/t/helper/test-drop-caches.c
@@ -155,7 +155,7 @@ static int cmd_dropcaches(void)
 
 #endif
 
-int cmd__drop_caches(int argc, const char **argv)
+int cmd__drop_caches(int argc UNUSED, const char **argv UNUSED)
 {
 	cmd_sync();
 	return cmd_dropcaches();
diff --git a/t/helper/test-dump-cache-tree.c b/t/helper/test-dump-cache-tree.c
index 92dfc1aa8c..ba1c5ce717 100644
--- a/t/helper/test-dump-cache-tree.c
+++ b/t/helper/test-dump-cache-tree.c
@@ -57,7 +57,7 @@ static int dump_cache_tree(struct cache_tree *it,
 	return errs;
 }
 
-int cmd__dump_cache_tree(int ac, const char **av)
+int cmd__dump_cache_tree(int ac UNUSED, const char **av UNUSED)
 {
 	struct index_state istate;
 	struct cache_tree *another = cache_tree();
diff --git a/t/helper/test-dump-fsmonitor.c b/t/helper/test-dump-fsmonitor.c
index 975f0ac890..3d2fb92ade 100644
--- a/t/helper/test-dump-fsmonitor.c
+++ b/t/helper/test-dump-fsmonitor.c
@@ -1,7 +1,7 @@
 #include "test-tool.h"
 #include "cache.h"
 
-int cmd__dump_fsmonitor(int ac, const char **av)
+int cmd__dump_fsmonitor(int ac UNUSED, const char **av UNUSED)
 {
 	struct index_state *istate = the_repository->index;
 	int i;
diff --git a/t/helper/test-dump-split-index.c b/t/helper/test-dump-split-index.c
index 813d0a38fa..4fabbdea49 100644
--- a/t/helper/test-dump-split-index.c
+++ b/t/helper/test-dump-split-index.c
@@ -10,7 +10,7 @@ static void show_bit(size_t pos, void *data)
 	printf(" %d", (int)pos);
 }
 
-int cmd__dump_split_index(int ac, const char **av)
+int cmd__dump_split_index(int ac UNUSED, const char **av)
 {
 	struct split_index *si;
 	int i;
diff --git a/t/helper/test-dump-untracked-cache.c b/t/helper/test-dump-untracked-cache.c
index af953fabe8..bc1ef8d4dc 100644
--- a/t/helper/test-dump-untracked-cache.c
+++ b/t/helper/test-dump-untracked-cache.c
@@ -41,7 +41,7 @@ static void dump(struct untracked_cache_dir *ucd, struct strbuf *base)
 	strbuf_setlen(base, len);
 }
 
-int cmd__dump_untracked_cache(int ac, const char **av)
+int cmd__dump_untracked_cache(int ac UNUSED, const char **av UNUSED)
 {
 	struct untracked_cache *uc;
 	struct strbuf base = STRBUF_INIT;
diff --git a/t/helper/test-example-decorate.c b/t/helper/test-example-decorate.c
index 7c7fc8efc1..2cf302ffcb 100644
--- a/t/helper/test-example-decorate.c
+++ b/t/helper/test-example-decorate.c
@@ -3,7 +3,7 @@
 #include "object.h"
 #include "decorate.h"
 
-int cmd__example_decorate(int argc, const char **argv)
+int cmd__example_decorate(int argc UNUSED, const char **argv UNUSED)
 {
 	struct decoration n;
 	struct object_id one_oid = { {1} };
diff --git a/t/helper/test-fsmonitor-client.c b/t/helper/test-fsmonitor-client.c
index 54a4856c48..0a1e492e5b 100644
--- a/t/helper/test-fsmonitor-client.c
+++ b/t/helper/test-fsmonitor-client.c
@@ -11,7 +11,7 @@
 #include "trace2.h"
 
 #ifndef HAVE_FSMONITOR_DAEMON_BACKEND
-int cmd__fsmonitor_client(int argc, const char **argv)
+int cmd__fsmonitor_client(int argc UNUSED, const char **argv UNUSED)
 {
 	die("fsmonitor--daemon not available on this platform");
 }
diff --git a/t/helper/test-hexdump.c b/t/helper/test-hexdump.c
index 811e89c1bc..05f55eca21 100644
--- a/t/helper/test-hexdump.c
+++ b/t/helper/test-hexdump.c
@@ -4,7 +4,7 @@
 /*
  * Read stdin and print a hexdump to stdout.
  */
-int cmd__hexdump(int argc, const char **argv)
+int cmd__hexdump(int argc UNUSED, const char **argv UNUSED)
 {
 	char buf[1024];
 	ssize_t i, len;
diff --git a/t/helper/test-index-version.c b/t/helper/test-index-version.c
index fcd10968cc..a06c45c1f8 100644
--- a/t/helper/test-index-version.c
+++ b/t/helper/test-index-version.c
@@ -1,7 +1,7 @@
 #include "test-tool.h"
 #include "cache.h"
 
-int cmd__index_version(int argc, const char **argv)
+int cmd__index_version(int argc UNUSED, const char **argv UNUSED)
 {
 	struct cache_header hdr;
 	int version;
diff --git a/t/helper/test-match-trees.c b/t/helper/test-match-trees.c
index 04bc2563f3..184aa1a087 100644
--- a/t/helper/test-match-trees.c
+++ b/t/helper/test-match-trees.c
@@ -3,7 +3,7 @@
 #include "hex.h"
 #include "tree.h"
 
-int cmd__match_trees(int ac, const char **av)
+int cmd__match_trees(int ac UNUSED, const char **av)
 {
 	struct object_id hash1, hash2, shifted;
 	struct tree *one, *two;
diff --git a/t/helper/test-oid-array.c b/t/helper/test-oid-array.c
index 0906993ad5..c3a1a00466 100644
--- a/t/helper/test-oid-array.c
+++ b/t/helper/test-oid-array.c
@@ -9,7 +9,7 @@ static int print_oid(const struct object_id *oid, void *data)
 	return 0;
 }
 
-int cmd__oid_array(int argc, const char **argv)
+int cmd__oid_array(int argc UNUSED, const char **argv UNUSED)
 {
 	struct oid_array array = OID_ARRAY_INIT;
 	struct strbuf line = STRBUF_INIT;
diff --git a/t/helper/test-oidmap.c b/t/helper/test-oidmap.c
index 883d40efd4..ee92ae8494 100644
--- a/t/helper/test-oidmap.c
+++ b/t/helper/test-oidmap.c
@@ -22,7 +22,7 @@ struct test_entry {
  * iterate -> oidkey1 namevalue1\noidkey2 namevalue2\n...
  *
  */
-int cmd__oidmap(int argc, const char **argv)
+int cmd__oidmap(int argc UNUSED, const char **argv UNUSED)
 {
 	struct strbuf line = STRBUF_INIT;
 	struct oidmap map = OIDMAP_INIT;
diff --git a/t/helper/test-oidtree.c b/t/helper/test-oidtree.c
index 0b82431a70..6a18e1bce8 100644
--- a/t/helper/test-oidtree.c
+++ b/t/helper/test-oidtree.c
@@ -3,13 +3,13 @@
 #include "hex.h"
 #include "oidtree.h"
 
-static enum cb_next print_oid(const struct object_id *oid, void *data)
+static enum cb_next print_oid(const struct object_id *oid, void *data UNUSED)
 {
 	puts(oid_to_hex(oid));
 	return CB_CONTINUE;
 }
 
-int cmd__oidtree(int argc, const char **argv)
+int cmd__oidtree(int argc UNUSED, const char **argv UNUSED)
 {
 	struct oidtree ot;
 	struct strbuf line = STRBUF_INIT;
diff --git a/t/helper/test-online-cpus.c b/t/helper/test-online-cpus.c
index 8cb0d53840..47dc211711 100644
--- a/t/helper/test-online-cpus.c
+++ b/t/helper/test-online-cpus.c
@@ -2,7 +2,7 @@
 #include "git-compat-util.h"
 #include "thread-utils.h"
 
-int cmd__online_cpus(int argc, const char **argv)
+int cmd__online_cpus(int argc UNUSED, const char **argv UNUSED)
 {
 	printf("%d\n", online_cpus());
 	return 0;
diff --git a/t/helper/test-parse-options.c b/t/helper/test-parse-options.c
index 506835521a..b66039e575 100644
--- a/t/helper/test-parse-options.c
+++ b/t/helper/test-parse-options.c
@@ -263,14 +263,14 @@ int cmd__parse_options_flags(int argc, const char **argv)
 	return parse_options_flags__cmd(argc, argv, test_flags);
 }
 
-static int subcmd_one(int argc, const char **argv, const char *prefix)
+static int subcmd_one(int argc, const char **argv, const char *prefix UNUSED)
 {
 	printf("fn: subcmd_one\n");
 	print_args(argc, argv);
 	return 0;
 }
 
-static int subcmd_two(int argc, const char **argv, const char *prefix)
+static int subcmd_two(int argc, const char **argv, const char *prefix UNUSED)
 {
 	printf("fn: subcmd_two\n");
 	print_args(argc, argv);
diff --git a/t/helper/test-prio-queue.c b/t/helper/test-prio-queue.c
index 4915412e07..f0bf255f5f 100644
--- a/t/helper/test-prio-queue.c
+++ b/t/helper/test-prio-queue.c
@@ -16,7 +16,7 @@ static void show(int *v)
 	free(v);
 }
 
-int cmd__prio_queue(int argc, const char **argv)
+int cmd__prio_queue(int argc UNUSED, const char **argv)
 {
 	struct prio_queue pq = { intcmp };
 
diff --git a/t/helper/test-read-graph.c b/t/helper/test-read-graph.c
index 98b73bb8f2..f92aea9d1f 100644
--- a/t/helper/test-read-graph.c
+++ b/t/helper/test-read-graph.c
@@ -5,7 +5,7 @@
 #include "object-store.h"
 #include "bloom.h"
 
-int cmd__read_graph(int argc, const char **argv)
+int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
 {
 	struct commit_graph *graph = NULL;
 	struct object_directory *odb;
diff --git a/t/helper/test-ref-store.c b/t/helper/test-ref-store.c
index 1745b088b7..31c79a777a 100644
--- a/t/helper/test-ref-store.c
+++ b/t/helper/test-ref-store.c
@@ -201,7 +201,8 @@ static int cmd_verify_ref(struct ref_store *refs, const char **argv)
 	return ret;
 }
 
-static int cmd_for_each_reflog(struct ref_store *refs, const char **argv)
+static int cmd_for_each_reflog(struct ref_store *refs,
+			       const char **argv UNUSED)
 {
 	return refs_for_each_reflog(refs, each_ref, NULL);
 }
@@ -323,7 +324,7 @@ static struct command commands[] = {
 	{ NULL, NULL }
 };
 
-int cmd__ref_store(int argc, const char **argv)
+int cmd__ref_store(int argc UNUSED, const char **argv)
 {
 	struct ref_store *refs;
 	const char *func;
diff --git a/t/helper/test-scrap-cache-tree.c b/t/helper/test-scrap-cache-tree.c
index a26107ed70..8a42c475b3 100644
--- a/t/helper/test-scrap-cache-tree.c
+++ b/t/helper/test-scrap-cache-tree.c
@@ -5,7 +5,7 @@
 #include "tree.h"
 #include "cache-tree.h"
 
-int cmd__scrap_cache_tree(int ac, const char **av)
+int cmd__scrap_cache_tree(int ac UNUSED, const char **av UNUSED)
 {
 	struct lock_file index_lock = LOCK_INIT;
 
diff --git a/t/helper/test-sigchain.c b/t/helper/test-sigchain.c
index d1cf7377b7..2d5ecf7383 100644
--- a/t/helper/test-sigchain.c
+++ b/t/helper/test-sigchain.c
@@ -13,7 +13,7 @@ X(two)
 X(three)
 #undef X
 
-int cmd__sigchain(int argc, const char **argv)
+int cmd__sigchain(int argc UNUSED, const char **argv UNUSED)
 {
 	sigchain_push(SIGTERM, one);
 	sigchain_push(SIGTERM, two);
diff --git a/t/helper/test-strcmp-offset.c b/t/helper/test-strcmp-offset.c
index 44e4a6d143..96b9a5b529 100644
--- a/t/helper/test-strcmp-offset.c
+++ b/t/helper/test-strcmp-offset.c
@@ -1,7 +1,7 @@
 #include "test-tool.h"
 #include "cache.h"
 
-int cmd__strcmp_offset(int argc, const char **argv)
+int cmd__strcmp_offset(int argc UNUSED, const char **argv)
 {
 	int result;
 	size_t offset;
diff --git a/t/helper/test-submodule-config.c b/t/helper/test-submodule-config.c
index 22a41c4092..edeee41abd 100644
--- a/t/helper/test-submodule-config.c
+++ b/t/helper/test-submodule-config.c
@@ -4,7 +4,7 @@
 #include "submodule-config.h"
 #include "submodule.h"
 
-static void die_usage(int argc, const char **argv, const char *msg)
+static void die_usage(int argc UNUSED, const char **argv, const char *msg)
 {
 	fprintf(stderr, "%s\n", msg);
 	fprintf(stderr, "Usage: %s [<commit> <submodulepath>] ...\n", argv[0]);
diff --git a/t/helper/test-submodule.c b/t/helper/test-submodule.c
index e060cc6226..3b75358723 100644
--- a/t/helper/test-submodule.c
+++ b/t/helper/test-submodule.c
@@ -174,7 +174,7 @@ static int cmd__submodule_config_unset(int argc, const char **argv)
 	usage_with_options(usage, options);
 }
 
-static int cmd__submodule_config_writeable(int argc, const char **argv)
+static int cmd__submodule_config_writeable(int argc, const char **argv UNUSED)
 {
 	struct option options[] = {
 		OPT_END()
diff --git a/t/helper/test-trace2.c b/t/helper/test-trace2.c
index f374c21ec3..688c8d017d 100644
--- a/t/helper/test-trace2.c
+++ b/t/helper/test-trace2.c
@@ -208,7 +208,7 @@ static int ut_007BUG(int argc, const char **argv)
 	BUG("the bug message");
 }
 
-static int ut_008bug(int argc, const char **argv)
+static int ut_008bug(int argc UNUSED, const char **argv UNUSED)
 {
 	bug("a bug message");
 	bug("another bug message");
@@ -216,7 +216,7 @@ static int ut_008bug(int argc, const char **argv)
 	return 0;
 }
 
-static int ut_009bug_BUG(int argc, const char **argv)
+static int ut_009bug_BUG(int argc UNUSED, const char **argv UNUSED)
 {
 	bug("a bug message");
 	bug("another bug message");
@@ -224,7 +224,7 @@ static int ut_009bug_BUG(int argc, const char **argv)
 	return 0;
 }
 
-static int ut_010bug_BUG(int argc, const char **argv)
+static int ut_010bug_BUG(int argc UNUSED, const char **argv UNUSED)
 {
 	bug("a %s message", "bug");
 	BUG("a %s message", "BUG");
diff --git a/t/helper/test-xml-encode.c b/t/helper/test-xml-encode.c
index a648bbd961..b2f330d1a4 100644
--- a/t/helper/test-xml-encode.c
+++ b/t/helper/test-xml-encode.c
@@ -6,7 +6,7 @@ static const char *utf8_replace_character = "&#xfffd;";
  * Encodes (possibly incorrect) UTF-8 on <stdin> to <stdout>, to be embedded
  * in an XML file.
  */
-int cmd__xml_encode(int argc, const char **argv)
+int cmd__xml_encode(int argc UNUSED, const char **argv UNUSED)
 {
 	unsigned char buf[1024], tmp[4], *tmp2 = NULL;
 	ssize_t cur = 0, len = 1, remaining = 0;
diff --git a/t/t9304-fast-import-marks.sh b/t/t9304-fast-import-marks.sh
index a98ef032d9..410a871c52 100755
--- a/t/t9304-fast-import-marks.sh
+++ b/t/t9304-fast-import-marks.sh
@@ -49,4 +49,33 @@ test_expect_success 'import with submodule mapping' '
 	test_cmp expect actual
 '
 
+test_expect_success 'paths adjusted for relative subdir' '
+	git init deep-dst &&
+	mkdir deep-dst/subdir &&
+	>deep-dst/subdir/empty-marks &&
+	git -C deep-dst/subdir fast-import \
+		--rewrite-submodules-from=sub:../../from \
+		--rewrite-submodules-to=sub:../../to \
+		--import-marks=empty-marks \
+		--export-marks=exported-marks \
+		--export-pack-edges=exported-edges \
+		<dump &&
+	# we do not bother checking resulting repo; we just care that nothing
+	# complained about failing to open files for reading, and that files
+	# for writing were created in the expected spot
+	test_path_is_file deep-dst/subdir/exported-marks &&
+	test_path_is_file deep-dst/subdir/exported-edges
+'
+
+test_expect_success 'relative marks are not affected by subdir' '
+	git init deep-relative &&
+	mkdir deep-relative/subdir &&
+	git -C deep-relative/subdir fast-import \
+		--relative-marks \
+		--export-marks=exported-marks \
+		<dump &&
+	test_path_is_missing deep-relative/subdir/exported-marks &&
+	test_path_is_file deep-relative/.git/info/fast-import/exported-marks
+'
+
 test_done