[...]

diff --git a/refs.h b/refs.h
index e010f8aec28..4dad8f24914 100644
--- a/refs.h
+++ b/refs.h

@@ -732,6 +732,17 @@ int update_ref(const char *msg, const char *refname,
 	       const struct object_id *new_oid, const struct object_id *old_oid,
 	       unsigned int flags, enum action_on_err onerr);
 
+/* Pseudorefs (eg. HEAD, CHERRY_PICK_HEAD) have a separate routines for updating
+   and deletion as they cannot take part in normal transactional updates.
+   Pseudorefs should only be written for the main repository.
+*/
+int refs_write_pseudoref(struct ref_store *refs, const char *pseudoref,
+			 const struct object_id *oid,
+			 const struct object_id *old_oid, struct strbuf *err);
+int refs_delete_pseudoref(struct ref_store *refs, const char *pseudoref,
+			  const struct object_id *old_oid);
+int delete_pseudoref(const char *pseudoref, const struct object_id *old_oid);
+

 int parse_hide_refs_config(const char *var, const char *value, const char *);
 
 /*

diff --git a/refs/files-backend.c b/refs/files-backend.c
index 6516c7bc8c8..df7553f4cc3 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c

@@ -731,6 +731,115 @@ static int lock_raw_ref(struct files_ref_store *refs,
 	return ret;
 }
 
+static int files_write_pseudoref(struct ref_store *ref_store,
+				 const char *pseudoref,
+				 const struct object_id *oid,
+				 const struct object_id *old_oid,
+				 struct strbuf *err)
+{
+	struct files_ref_store *refs =
+		files_downcast(ref_store, REF_STORE_READ, "write_pseudoref");
+	int fd;
+	struct lock_file lock = LOCK_INIT;
+	struct strbuf filename = STRBUF_INIT;
+	struct strbuf buf = STRBUF_INIT;
+	int ret = -1;
+
+	if (!oid)
+		return 0;
+
+	strbuf_addf(&filename, "%s/%s", refs->gitdir, pseudoref);
+	fd = hold_lock_file_for_update_timeout(&lock, filename.buf, 0,
+					       get_files_ref_lock_timeout_ms());
+	if (fd < 0) {
+		strbuf_addf(err, _("could not open '%s' for writing: %s"),
+			    buf.buf, strerror(errno));
+		goto done;
+	}
+
+	if (old_oid) {
+		struct object_id actual_old_oid;
+
+		if (read_ref(pseudoref, &actual_old_oid)) {
+			if (!is_null_oid(old_oid)) {
+				strbuf_addf(err, _("could not read ref '%s'"),
+					    pseudoref);
+				rollback_lock_file(&lock);
+				goto done;
+			}
+		} else if (is_null_oid(old_oid)) {
+			strbuf_addf(err, _("ref '%s' already exists"),
+				    pseudoref);
+			rollback_lock_file(&lock);
+			goto done;
+		} else if (!oideq(&actual_old_oid, old_oid)) {
+			strbuf_addf(err,
+				    _("unexpected object ID when writing '%s'"),
+				    pseudoref);
+			rollback_lock_file(&lock);
+			goto done;
+		}
+	}
+
+	strbuf_addf(&buf, "%s\n", oid_to_hex(oid));
+	if (write_in_full(fd, buf.buf, buf.len) < 0) {
+		strbuf_addf(err, _("could not write to '%s'"), filename.buf);
+		rollback_lock_file(&lock);
+		goto done;
+	}
+
+	commit_lock_file(&lock);
+	ret = 0;
+done:
+	strbuf_release(&buf);
+	strbuf_release(&filename);
+	return ret;
+}
+
+static int files_delete_pseudoref(struct ref_store *ref_store,
+				  const char *pseudoref,
+				  const struct object_id *old_oid)
+{
+	struct files_ref_store *refs =
+		files_downcast(ref_store, REF_STORE_READ, "delete_pseudoref");
+	struct strbuf filename = STRBUF_INIT;
+	int ret = -1;
+
+	strbuf_addf(&filename, "%s/%s", refs->gitdir, pseudoref);
+
+	if (old_oid && !is_null_oid(old_oid)) {
+		struct lock_file lock = LOCK_INIT;
+		int fd;
+		struct object_id actual_old_oid;
+
+		fd = hold_lock_file_for_update_timeout(
+			&lock, filename.buf, 0,
+			get_files_ref_lock_timeout_ms());
+		if (fd < 0) {
+			error_errno(_("could not open '%s' for writing"),
+				    filename.buf);
+			goto done;
+		}
+		if (read_ref(pseudoref, &actual_old_oid))
+			die(_("could not read ref '%s'"), pseudoref);
+		if (!oideq(&actual_old_oid, old_oid)) {
+			error(_("unexpected object ID when deleting '%s'"),
+			      pseudoref);
+			rollback_lock_file(&lock);
+			goto done;
+		}
+
+		unlink(filename.buf);

+		rollback_lock_file(&lock);
+	} else {
+		unlink(filename.buf);
+	}
+	ret = 0;
+done:
+	strbuf_release(&filename);
+	return ret;
+}
+
 struct files_ref_iterator {
 	struct ref_iterator base;
 

@@ -3189,6 +3298,9 @@ struct ref_storage_be refs_be_files = {
 	files_rename_ref,
 	files_copy_ref,
 
+	files_write_pseudoref,
+	files_delete_pseudoref,
+
 	files_ref_iterator_begin,
 	files_read_raw_ref,
 

@@ -3198,5 +3310,5 @@ struct ref_storage_be refs_be_files = {
 	files_reflog_exists,
 	files_create_reflog,
 	files_delete_reflog,
-	files_reflog_expire
+	files_reflog_expire,
 };

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 4458a0f69cc..08e8253a893 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c

@@ -1590,6 +1590,22 @@ static int packed_copy_ref(struct ref_store *ref_store,
 	BUG("packed reference store does not support copying references");
 }
 
+static int packed_write_pseudoref(struct ref_store *ref_store,
+				  const char *pseudoref,
+				  const struct object_id *oid,
+				  const struct object_id *old_oid,
+				  struct strbuf *err)
+{
+	BUG("packed reference store does not support writing pseudo-references");
+}
+
+static int packed_delete_pseudoref(struct ref_store *ref_store,
+				   const char *pseudoref,
+				   const struct object_id *old_oid)
+{
+	BUG("packed reference store does not support deleting pseudo-references");
+}
+
 static struct ref_iterator *packed_reflog_iterator_begin(struct ref_store *ref_store)
 {
 	return empty_ref_iterator_begin();

@@ -1656,6 +1672,9 @@ struct ref_storage_be refs_be_packed = {
 	packed_rename_ref,
 	packed_copy_ref,
 
+	packed_write_pseudoref,
+	packed_delete_pseudoref,
+
 	packed_ref_iterator_begin,
 	packed_read_raw_ref,
 

@@ -1665,5 +1684,5 @@ struct ref_storage_be refs_be_packed = {
 	packed_reflog_exists,
 	packed_create_reflog,
 	packed_delete_reflog,
-	packed_reflog_expire
+	packed_reflog_expire,
 };

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 4271362d264..59b053d53a2 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h

@@ -556,6 +556,21 @@ typedef int copy_ref_fn(struct ref_store *ref_store,
 			  const char *oldref, const char *newref,
 			  const char *logmsg);
 
+typedef int write_pseudoref_fn(struct ref_store *ref_store,
+			       const char *pseudoref,
+			       const struct object_id *oid,
+			       const struct object_id *old_oid,
+			       struct strbuf *err);
+
+/*
+ * Deletes a pseudoref. Deletion always succeeds (even if the pseudoref doesn't
+ * exist.), except if old_oid is specified. If it is, it can fail due to lock
+ * failure, failure reading the old OID, or an OID mismatch
+ */
+typedef int delete_pseudoref_fn(struct ref_store *ref_store,
+				const char *pseudoref,
+				const struct object_id *old_oid);
+
 /*
  * Iterate over the references in `ref_store` whose names start with
  * `prefix`. `prefix` is matched as a literal string, without regard

@@ -655,6 +670,9 @@ struct ref_storage_be {
 	rename_ref_fn *rename_ref;
 	copy_ref_fn *copy_ref;
 
+	write_pseudoref_fn *write_pseudoref;
+	delete_pseudoref_fn *delete_pseudoref;
+
 	ref_iterator_begin_fn *iterator_begin;
 	read_raw_ref_fn *read_raw_ref;