diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index dada55884a..878aa7f0ed 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1029,8 +1029,8 @@ static int read_proc_receive_report(struct packet_reader *reader,
 
 	for (;;) {
 		struct object_id old_oid, new_oid;
-		const char *head;
-		const char *refname;
+		char *head;
+		char *refname;
 		char *p;
 		enum packet_read_status status;
 
@@ -1054,7 +1054,8 @@ static int read_proc_receive_report(struct packet_reader *reader,
 		}
 		*p++ = '\0';
 		if (!strcmp(head, "option")) {
-			const char *key, *val;
+			char *key;
+			const char *val;
 
 			if (!hint || !(report || new_report)) {
 				if (!once++)
diff --git a/convert.c b/convert.c
index a34ec6ecdc..eae36c8a59 100644
--- a/convert.c
+++ b/convert.c
@@ -1168,7 +1168,8 @@ static int ident_to_worktree(const char *src, size_t len,
 			     struct strbuf *buf, int ident)
 {
 	struct object_id oid;
-	char *to_free = NULL, *dollar, *spc;
+	char *to_free = NULL;
+	const char *dollar, *spc;
 	int cnt;
 
 	if (!ident)
diff --git a/git-compat-util.h b/git-compat-util.h
index 4b4ea2498f..ae1bdc90a4 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -335,11 +335,7 @@ static inline int is_path_owned_by_current_uid(const char *path,
 #endif
 
 #ifndef find_last_dir_sep
-static inline char *git_find_last_dir_sep(const char *path)
-{
-	return strrchr(path, '/');
-}
-#define find_last_dir_sep git_find_last_dir_sep
+#define find_last_dir_sep(path) strrchr((path), '/')
 #endif
 
 #ifndef has_dir_sep
@@ -467,6 +463,21 @@ void set_warn_routine(report_fn routine);
 report_fn get_warn_routine(void);
 void set_die_is_recursing_routine(int (*routine)(void));
 
+/*
+ * Check that an out-parameter is "at least as const as" a matching
+ * in-parameter. For example, skip_prefix() will return "out" that is a subset
+ * of "str". So:
+ *
+ *  const str, const out: ok
+ *  non-const str, const out: ok
+ *  non-const str, non-const out: ok
+ *  const str, non-const out: compile error
+ *
+ *  See the skip_prefix macro below for an example of use.
+ */
+#define CONST_OUTPARAM(in, out) \
+	((const char **)(0 ? ((*(out) = (in)),(out)) : (out)))
+
 /*
  * If the string "str" begins with the string found in "prefix", return true.
  * The "out" parameter is set to "str + strlen(prefix)" (i.e., to the point in
@@ -483,8 +494,10 @@ void set_die_is_recursing_routine(int (*routine)(void));
  *   [skip prefix if present, otherwise use whole string]
  *   skip_prefix(name, "refs/heads/", &name);
  */
-static inline bool skip_prefix(const char *str, const char *prefix,
-			       const char **out)
+#define skip_prefix(str, prefix, out) \
+	skip_prefix_impl((str), (prefix), CONST_OUTPARAM((str), (out)))
+static inline bool skip_prefix_impl(const char *str, const char *prefix,
+				    const char **out)
 {
 	do {
 		if (!*prefix) {
@@ -889,8 +902,10 @@ static inline size_t xsize_t(off_t len)
  * is done via tolower(), so it is strictly ASCII (no multi-byte characters or
  * locale-specific conversions).
  */
-static inline bool skip_iprefix(const char *str, const char *prefix,
-			       const char **out)
+#define skip_iprefix(str, prefix, out) \
+	skip_iprefix_impl((str), (prefix), CONST_OUTPARAM((str), (out)))
+static inline bool skip_iprefix_impl(const char *str, const char *prefix,
+				     const char **out)
 {
 	do {
 		if (!*prefix) {
diff --git a/hex.c b/hex.c
index 865a232167..bc756722ca 100644
--- a/hex.c
+++ b/hex.c
@@ -54,9 +54,9 @@ int get_oid_hex(const char *hex, struct object_id *oid)
 	return get_oid_hex_algop(hex, oid, the_hash_algo);
 }
 
-int parse_oid_hex_algop(const char *hex, struct object_id *oid,
-			const char **end,
-			const struct git_hash_algo *algop)
+int parse_oid_hex_algop_impl(const char *hex, struct object_id *oid,
+			     const char **end,
+			     const struct git_hash_algo *algop)
 {
 	int ret = get_oid_hex_algop(hex, oid, algop);
 	if (!ret)
diff --git a/hex.h b/hex.h
index e9ccb54065..1e9a65d83a 100644
--- a/hex.h
+++ b/hex.h
@@ -40,8 +40,10 @@ char *oid_to_hex(const struct object_id *oid);						/* same static buffer */
  * other invalid character.  end is only updated on success; otherwise, it is
  * unmodified.
  */
-int parse_oid_hex_algop(const char *hex, struct object_id *oid, const char **end,
-			const struct git_hash_algo *algo);
+#define parse_oid_hex_algop(hex, oid, end, algo) \
+	parse_oid_hex_algop_impl((hex), (oid), CONST_OUTPARAM((hex), (end)), (algo))
+int parse_oid_hex_algop_impl(const char *hex, struct object_id *oid, const char **end,
+			     const struct git_hash_algo *algo);
 
 /*
  * These functions work like get_oid_hex and parse_oid_hex, but they will parse
diff --git a/http-push.c b/http-push.c
index 06c3acbb5d..d143fe2845 100644
--- a/http-push.c
+++ b/http-push.c
@@ -99,7 +99,7 @@ static struct object_list *objects;
 
 struct repo {
 	char *url;
-	char *path;
+	const char *path;
 	int path_len;
 	int has_info_refs;
 	int can_update_info_refs;
diff --git a/http.c b/http.c
index d8d016891b..67c9c6fc60 100644
--- a/http.c
+++ b/http.c
@@ -748,7 +748,7 @@ static int has_proxy_cert_password(void)
 static int redact_sensitive_header(struct strbuf *header, size_t offset)
 {
 	int ret = 0;
-	const char *sensitive_header;
+	char *sensitive_header;
 
 	if (trace_curl_redact &&
 	    (skip_iprefix(header->buf + offset, "Authorization:", &sensitive_header) ||
@@ -765,7 +765,7 @@ static int redact_sensitive_header(struct strbuf *header, size_t offset)
 	} else if (trace_curl_redact &&
 		   skip_iprefix(header->buf + offset, "Cookie:", &sensitive_header)) {
 		struct strbuf redacted_header = STRBUF_INIT;
-		const char *cookie;
+		char *cookie;
 
 		while (isspace(*sensitive_header))
 			sensitive_header++;
diff --git a/pager.c b/pager.c
index 5531fff50e..35b210e048 100644
--- a/pager.c
+++ b/pager.c
@@ -108,10 +108,11 @@ const char *git_pager(struct repository *r, int stdout_is_tty)
 
 static void setup_pager_env(struct strvec *env)
 {
-	const char **argv;
+	char **argv;
 	int i;
 	char *pager_env = xstrdup(PAGER_ENV);
-	int n = split_cmdline(pager_env, &argv);
+	/* split_cmdline splits in place, so we know the result is writable */
+	int n = split_cmdline(pager_env, (const char ***)&argv);
 
 	if (n < 0)
 		die("malformed build-time PAGER_ENV: %s",
diff --git a/pkt-line.h b/pkt-line.h
index 3b33cc64f3..e6cf85e34e 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -184,7 +184,7 @@ struct packet_reader {
 	int pktlen;
 
 	/* the last line read */
-	const char *line;
+	char *line;
 
 	/* indicates if a line has been peeked */
 	int line_peeked;
diff --git a/pseudo-merge.c b/pseudo-merge.c
index a2d5bd85f9..ff18b6c364 100644
--- a/pseudo-merge.c
+++ b/pseudo-merge.c
@@ -638,14 +638,21 @@ static int pseudo_merge_commit_cmp(const void *va, const void *vb)
 	return 0;
 }
 
-static struct pseudo_merge_commit *find_pseudo_merge(const struct pseudo_merge_map *pm,
-						     uint32_t pos)
+static int find_pseudo_merge(const struct pseudo_merge_map *pm, uint32_t pos,
+			     struct pseudo_merge_commit *out)
 {
-	if (!pm->commits_nr)
-		return NULL;
+	const unsigned char *at;
 
-	return bsearch(&pos, pm->commits, pm->commits_nr,
-		       PSEUDO_MERGE_COMMIT_RAWSZ, pseudo_merge_commit_cmp);
+	if (!pm->commits_nr)
+		return 0;
+
+	at = bsearch(&pos, pm->commits, pm->commits_nr,
+		     PSEUDO_MERGE_COMMIT_RAWSZ, pseudo_merge_commit_cmp);
+	if (!at)
+		return 0;
+
+	read_pseudo_merge_commit_at(out, at);
+	return 1;
 }
 
 int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
@@ -653,16 +660,15 @@ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 				   struct commit *commit, uint32_t commit_pos)
 {
 	struct pseudo_merge *merge;
-	struct pseudo_merge_commit *merge_commit;
+	struct pseudo_merge_commit merge_commit;
 	int ret = 0;
 
-	merge_commit = find_pseudo_merge(pm, commit_pos);
-	if (!merge_commit)
+	if (!find_pseudo_merge(pm, commit_pos, &merge_commit))
 		return 0;
 
-	if (merge_commit->pseudo_merge_ofs & ((uint64_t)1<<63)) {
+	if (merge_commit.pseudo_merge_ofs & ((uint64_t)1<<63)) {
 		struct pseudo_merge_commit_ext ext = { 0 };
-		off_t ofs = merge_commit->pseudo_merge_ofs & ~((uint64_t)1<<63);
+		off_t ofs = merge_commit.pseudo_merge_ofs & ~((uint64_t)1<<63);
 		uint32_t i;
 
 		if (pseudo_merge_ext_at(pm, &ext, ofs) < -1) {
@@ -673,11 +679,11 @@ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 		}
 
 		for (i = 0; i < ext.nr; i++) {
-			if (nth_pseudo_merge_ext(pm, &ext, merge_commit, i) < 0)
+			if (nth_pseudo_merge_ext(pm, &ext, &merge_commit, i) < 0)
 				return ret;
 
 			merge = pseudo_merge_at(pm, &commit->object.oid,
-						merge_commit->pseudo_merge_ofs);
+						merge_commit.pseudo_merge_ofs);
 
 			if (!merge)
 				return ret;
@@ -687,7 +693,7 @@ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 		}
 	} else {
 		merge = pseudo_merge_at(pm, &commit->object.oid,
-					merge_commit->pseudo_merge_ofs);
+					merge_commit.pseudo_merge_ofs);
 
 		if (!merge)
 			return ret;
diff --git a/range-diff.c b/range-diff.c
index 2712a9a107..8e2dd2eb19 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -88,7 +88,7 @@ static int read_patches(const char *range, struct string_list *list,
 	line = contents.buf;
 	size = contents.len;
 	for (; size > 0; size -= len, line += len) {
-		const char *p;
+		char *p;
 		char *eol;
 
 		eol = memchr(line, '\n', size);
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 0537a72b2a..b3b0c25f84 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -2190,7 +2190,7 @@ static int show_one_reflog_ent(struct files_ref_store *refs,
 	char *email_end, *message;
 	timestamp_t timestamp;
 	int tz;
-	const char *p = sb->buf;
+	char *p = sb->buf;
 
 	/* old SP new SP name <email> SP time TAB msg LF */
 	if (!sb->len || sb->buf[sb->len - 1] != '\n' ||
diff --git a/run-command.c b/run-command.c
index 574d5c40f0..c146a56532 100644
--- a/run-command.c
+++ b/run-command.c
@@ -604,11 +604,11 @@ static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 	/* Last one wins, see run-command.c:prep_childenv() for context */
 	for (e = deltaenv; e && *e; e++) {
 		struct strbuf key = STRBUF_INIT;
-		char *equals = strchr(*e, '=');
+		const char *equals = strchr(*e, '=');
 
 		if (equals) {
 			strbuf_add(&key, *e, equals - *e);
-			string_list_insert(&envs, key.buf)->util = equals + 1;
+			string_list_insert(&envs, key.buf)->util = (void *)(equals + 1);
 		} else {
 			string_list_insert(&envs, *e)->util = NULL;
 		}
diff --git a/send-pack.c b/send-pack.c
index 07ecfae4de..b4361d5610 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -175,8 +175,8 @@ static int receive_status(struct repository *r,
 	ret = receive_unpack_status(reader);
 	while (1) {
 		struct object_id old_oid, new_oid;
-		const char *head;
-		const char *refname;
+		char *head;
+		char *refname;
 		char *p;
 		if (packet_reader_read(reader) != PACKET_READ_NORMAL)
 			break;
@@ -190,7 +190,8 @@ static int receive_status(struct repository *r,
 		*p++ = '\0';
 
 		if (!strcmp(head, "option")) {
-			const char *key, *val;
+			char *key;
+			const char *val;
 
 			if (!hint || !(report || new_report)) {
 				if (!once++)
diff --git a/transport-helper.c b/transport-helper.c
index 570d7c6439..4e5d1d914f 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -783,7 +783,8 @@ static int push_update_ref_status(struct strbuf *buf,
 
 	if (starts_with(buf->buf, "option ")) {
 		struct object_id old_oid, new_oid;
-		const char *key, *val;
+		char *key;
+		const char *val;
 		char *p;
 
 		if (!state->hint || !(state->report || state->new_report))