diff --git a/builtin/fetch.c b/builtin/fetch.c
index 3ae52c015d..95beed57fa 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -27,6 +27,7 @@
 #include "branch.h"
 #include "promisor-remote.h"
 #include "commit-graph.h"
+#include "shallow.h"
 
 #define FORCED_UPDATES_DELAY_WARNING_IN_MS (10 * 1000)
 
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 03b85f5166..c5b433a23f 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -34,6 +34,7 @@
 #include "dir.h"
 #include "midx.h"
 #include "trace2.h"
+#include "shallow.h"
 
 #define IN_PACK(obj) oe_in_pack(&to_pack, obj)
 #define SIZE(obj) oe_size(&to_pack, obj)
diff --git a/builtin/prune.c b/builtin/prune.c
index fd9acc7222..02c6ab7cba 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -8,6 +8,7 @@
 #include "progress.h"
 #include "prune-packed.h"
 #include "object-store.h"
+#include "shallow.h"
 
 static const char * const prune_usage[] = {
 	N_("git prune [-n] [-v] [--progress] [--expire <time>] [--] [<head>...]"),
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index d37ab776b3..ea3d0f01af 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -28,6 +28,7 @@
 #include "protocol.h"
 #include "commit-reach.h"
 #include "worktree.h"
+#include "shallow.h"
 
 static const char * const receive_pack_usage[] = {
 	N_("git receive-pack <git-dir>"),
@@ -876,7 +877,7 @@ static void refuse_unconfigured_deny_delete_current(void)
 static int command_singleton_iterator(void *cb_data, struct object_id *oid);
 static int update_shallow_ref(struct command *cmd, struct shallow_info *si)
 {
-	struct lock_file shallow_lock = LOCK_INIT;
+	struct shallow_lock shallow_lock = SHALLOW_LOCK_INIT;
 	struct oid_array extra = OID_ARRAY_INIT;
 	struct check_connected_options opt = CHECK_CONNECTED_INIT;
 	uint32_t mask = 1 << (cmd->index % 32);
diff --git a/builtin/repack.c b/builtin/repack.c
index 1b686ee9ce..df287739d9 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -13,6 +13,7 @@
 #include "prune-packed.h"
 #include "object-store.h"
 #include "promisor-remote.h"
+#include "shallow.h"
 
 static int delta_base_offset = 1;
 static int pack_kept_objects = -1;
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 06056434ed..669dd2fd6f 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -16,6 +16,7 @@
 #include "split-index.h"
 #include "submodule.h"
 #include "commit-reach.h"
+#include "shallow.h"
 
 #define DO_REVS		1
 #define DO_NOREV	2
diff --git a/commit-graph.c b/commit-graph.c
index 5ea0c8e15c..e3420ddcbf 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -18,6 +18,7 @@
 #include "progress.h"
 #include "bloom.h"
 #include "commit-slab.h"
+#include "shallow.h"
 
 void git_test_write_commit_graph_or_die(void)
 {
diff --git a/commit.c b/commit.c
index c7099daeac..87686a7055 100644
--- a/commit.c
+++ b/commit.c
@@ -20,6 +20,7 @@
 #include "refs.h"
 #include "commit-reach.h"
 #include "run-command.h"
+#include "shallow.h"
 
 static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
 
@@ -110,7 +111,7 @@ static const unsigned char *commit_graft_sha1_access(size_t index, void *table)
 	return commit_graft_table[index]->oid.hash;
 }
 
-static int commit_graft_pos(struct repository *r, const unsigned char *sha1)
+int commit_graft_pos(struct repository *r, const unsigned char *sha1)
 {
 	return sha1_pos(sha1, r->parsed_objects->grafts,
 			r->parsed_objects->grafts_nr,
@@ -245,19 +246,6 @@ int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
 	return ret;
 }
 
-int unregister_shallow(const struct object_id *oid)
-{
-	int pos = commit_graft_pos(the_repository, oid->hash);
-	if (pos < 0)
-		return -1;
-	if (pos + 1 < the_repository->parsed_objects->grafts_nr)
-		MOVE_ARRAY(the_repository->parsed_objects->grafts + pos,
-			   the_repository->parsed_objects->grafts + pos + 1,
-			   the_repository->parsed_objects->grafts_nr - pos - 1);
-	the_repository->parsed_objects->grafts_nr--;
-	return 0;
-}
-
 struct commit_buffer {
 	void *buffer;
 	unsigned long size;
diff --git a/commit.h b/commit.h
index ab91d21131..1b2dea5d85 100644
--- a/commit.h
+++ b/commit.h
@@ -236,6 +236,8 @@ struct commit_graft {
 typedef int (*each_commit_graft_fn)(const struct commit_graft *, void *);
 
 struct commit_graft *read_graft_line(struct strbuf *line);
+/* commit_graft_pos returns an index into r->parsed_objects->grafts. */
+int commit_graft_pos(struct repository *r, const unsigned char *sha1);
 int register_commit_graft(struct repository *r, struct commit_graft *, int);
 void prepare_commit_graft(struct repository *r);
 struct commit_graft *lookup_commit_graft(struct repository *r, const struct object_id *oid);
@@ -247,55 +249,7 @@ struct commit *get_fork_point(const char *refname, struct commit *commit);
 
 struct oid_array;
 struct ref;
-int register_shallow(struct repository *r, const struct object_id *oid);
-int unregister_shallow(const struct object_id *oid);
-int commit_shallow_file(struct repository *r, struct lock_file *lk);
-void rollback_shallow_file(struct repository *r, struct lock_file *lk);
 int for_each_commit_graft(each_commit_graft_fn, void *);
-int is_repository_shallow(struct repository *r);
-struct commit_list *get_shallow_commits(struct object_array *heads,
-					int depth, int shallow_flag, int not_shallow_flag);
-struct commit_list *get_shallow_commits_by_rev_list(
-		int ac, const char **av, int shallow_flag, int not_shallow_flag);
-void set_alternate_shallow_file(struct repository *r, const char *path, int override);
-int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
-			  const struct oid_array *extra);
-void setup_alternate_shallow(struct lock_file *shallow_lock,
-			     const char **alternate_shallow_file,
-			     const struct oid_array *extra);
-const char *setup_temporary_shallow(const struct oid_array *extra);
-void advertise_shallow_grafts(int);
-
-/*
- * Initialize with prepare_shallow_info() or zero-initialize (equivalent to
- * prepare_shallow_info with a NULL oid_array).
- */
-struct shallow_info {
-	struct oid_array *shallow;
-	int *ours, nr_ours;
-	int *theirs, nr_theirs;
-	struct oid_array *ref;
-
-	/* for receive-pack */
-	uint32_t **used_shallow;
-	int *need_reachability_test;
-	int *reachable;
-	int *shallow_ref;
-	struct commit **commits;
-	int nr_commits;
-};
-
-void prepare_shallow_info(struct shallow_info *, struct oid_array *);
-void clear_shallow_info(struct shallow_info *);
-void remove_nonexistent_theirs_shallow(struct shallow_info *);
-void assign_shallow_commits_to_refs(struct shallow_info *info,
-				    uint32_t **used,
-				    int *ref_status);
-int delayed_reachability_test(struct shallow_info *si, int c);
-#define PRUNE_SHOW_ONLY 1
-#define PRUNE_QUICK 2
-void prune_shallow(unsigned options);
-extern struct trace_key trace_shallow;
 
 int interactive_add(int argc, const char **argv, const char *prefix, int patch);
 int run_add_interactive(const char *revision, const char *patch_mode,
diff --git a/environment.c b/environment.c
index 10c9061c43..aaca0e91ac 100644
--- a/environment.c
+++ b/environment.c
@@ -17,6 +17,7 @@
 #include "argv-array.h"
 #include "object-store.h"
 #include "chdir-notify.h"
+#include "shallow.h"
 
 int trust_executable_bit = 1;
 int trust_ctime = 1;
diff --git a/fetch-pack.c b/fetch-pack.c
index f73a2ce6cb..7eaa19d7c1 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -22,6 +22,7 @@
 #include "connected.h"
 #include "fetch-negotiator.h"
 #include "fsck.h"
+#include "shallow.h"
 
 static int transfer_unpack_limit = -1;
 static int fetch_unpack_limit = -1;
@@ -34,7 +35,7 @@ static int fetch_fsck_objects = -1;
 static int transfer_fsck_objects = -1;
 static int agent_supported;
 static int server_supports_filtering;
-static struct lock_file shallow_lock;
+static struct shallow_lock shallow_lock;
 static const char *alternate_shallow_file;
 static struct strbuf fsck_msg_types = STRBUF_INIT;
 
diff --git a/git.c b/git.c
index 2e4efb4ff0..a2d337eed7 100644
--- a/git.c
+++ b/git.c
@@ -4,6 +4,7 @@
 #include "help.h"
 #include "run-command.h"
 #include "alias.h"
+#include "shallow.h"
 
 #define RUN_SETUP		(1<<0)
 #define RUN_SETUP_GENTLY	(1<<1)
diff --git a/send-pack.c b/send-pack.c
index d1b7edc995..0abee22283 100644
--- a/send-pack.c
+++ b/send-pack.c
@@ -15,6 +15,7 @@
 #include "oid-array.h"
 #include "gpg-interface.h"
 #include "cache.h"
+#include "shallow.h"
 
 int option_parse_push_signed(const struct option *opt,
 			     const char *arg, int unset)
diff --git a/shallow.c b/shallow.c
index 321a27670f..b826de9b67 100644
--- a/shallow.c
+++ b/shallow.c
@@ -14,6 +14,7 @@
 #include "commit-slab.h"
 #include "list-objects.h"
 #include "commit-reach.h"
+#include "shallow.h"
 
 void set_alternate_shallow_file(struct repository *r, const char *path, int override)
 {
@@ -38,6 +39,19 @@ int register_shallow(struct repository *r, const struct object_id *oid)
 	return register_commit_graft(r, graft, 0);
 }
 
+int unregister_shallow(const struct object_id *oid)
+{
+	int pos = commit_graft_pos(the_repository, oid->hash);
+	if (pos < 0)
+		return -1;
+	if (pos + 1 < the_repository->parsed_objects->grafts_nr)
+		MOVE_ARRAY(the_repository->parsed_objects->grafts + pos,
+			   the_repository->parsed_objects->grafts + pos + 1,
+			   the_repository->parsed_objects->grafts_nr - pos - 1);
+	the_repository->parsed_objects->grafts_nr--;
+	return 0;
+}
+
 int is_repository_shallow(struct repository *r)
 {
 	FILE *fp;
@@ -78,16 +92,16 @@ static void reset_repository_shallow(struct repository *r)
 	stat_validity_clear(r->parsed_objects->shallow_stat);
 }
 
-int commit_shallow_file(struct repository *r, struct lock_file *lk)
+int commit_shallow_file(struct repository *r, struct shallow_lock *lk)
 {
-	int res = commit_lock_file(lk);
+	int res = commit_lock_file(&lk->lock);
 	reset_repository_shallow(r);
 	return res;
 }
 
-void rollback_shallow_file(struct repository *r, struct lock_file *lk)
+void rollback_shallow_file(struct repository *r, struct shallow_lock *lk)
 {
-	rollback_lock_file(lk);
+	rollback_lock_file(&lk->lock);
 	reset_repository_shallow(r);
 }
 
@@ -352,22 +366,22 @@ const char *setup_temporary_shallow(const struct oid_array *extra)
 	return "";
 }
 
-void setup_alternate_shallow(struct lock_file *shallow_lock,
+void setup_alternate_shallow(struct shallow_lock *shallow_lock,
 			     const char **alternate_shallow_file,
 			     const struct oid_array *extra)
 {
 	struct strbuf sb = STRBUF_INIT;
 	int fd;
 
-	fd = hold_lock_file_for_update(shallow_lock,
+	fd = hold_lock_file_for_update(&shallow_lock->lock,
 				       git_path_shallow(the_repository),
 				       LOCK_DIE_ON_ERROR);
 	check_shallow_file_for_update(the_repository);
 	if (write_shallow_commits(&sb, 0, extra)) {
 		if (write_in_full(fd, sb.buf, sb.len) < 0)
 			die_errno("failed to write to %s",
-				  get_lock_file_path(shallow_lock));
-		*alternate_shallow_file = get_lock_file_path(shallow_lock);
+				  get_lock_file_path(&shallow_lock->lock));
+		*alternate_shallow_file = get_lock_file_path(&shallow_lock->lock);
 	} else
 		/*
 		 * is_repository_shallow() sees empty string as "no
@@ -400,7 +414,7 @@ void advertise_shallow_grafts(int fd)
  */
 void prune_shallow(unsigned options)
 {
-	struct lock_file shallow_lock = LOCK_INIT;
+	struct shallow_lock shallow_lock = SHALLOW_LOCK_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	unsigned flags = SEEN_ONLY;
 	int fd;
@@ -414,14 +428,14 @@ void prune_shallow(unsigned options)
 		strbuf_release(&sb);
 		return;
 	}
-	fd = hold_lock_file_for_update(&shallow_lock,
+	fd = hold_lock_file_for_update(&shallow_lock.lock,
 				       git_path_shallow(the_repository),
 				       LOCK_DIE_ON_ERROR);
 	check_shallow_file_for_update(the_repository);
 	if (write_shallow_commits_1(&sb, 0, NULL, flags)) {
 		if (write_in_full(fd, sb.buf, sb.len) < 0)
 			die_errno("failed to write to %s",
-				  get_lock_file_path(&shallow_lock));
+				  get_lock_file_path(&shallow_lock.lock));
 		commit_shallow_file(the_repository, &shallow_lock);
 	} else {
 		unlink(git_path_shallow(the_repository));
diff --git a/shallow.h b/shallow.h
new file mode 100644
index 0000000000..5b4a96dcd6
--- /dev/null
+++ b/shallow.h
@@ -0,0 +1,81 @@
+#ifndef SHALLOW_H
+#define SHALLOW_H
+
+#include "lockfile.h"
+#include "object.h"
+#include "repository.h"
+#include "strbuf.h"
+
+void set_alternate_shallow_file(struct repository *r, const char *path, int override);
+int register_shallow(struct repository *r, const struct object_id *oid);
+int unregister_shallow(const struct object_id *oid);
+int is_repository_shallow(struct repository *r);
+
+/*
+ * Lock for updating the $GIT_DIR/shallow file.
+ *
+ * Use `commit_shallow_file()` to commit an update, or
+ * `rollback_shallow_file()` to roll it back. In either case, any
+ * in-memory cached information about which commits are shallow will be
+ * appropriately invalidated so that future operations reflect the new
+ * state.
+ */
+struct shallow_lock {
+	struct lock_file lock;
+};
+#define SHALLOW_LOCK_INIT { LOCK_INIT }
+
+/* commit $GIT_DIR/shallow and reset stat-validity checks */
+int commit_shallow_file(struct repository *r, struct shallow_lock *lk);
+/* rollback $GIT_DIR/shallow and reset stat-validity checks */
+void rollback_shallow_file(struct repository *r, struct shallow_lock *lk);
+
+struct commit_list *get_shallow_commits(struct object_array *heads,
+					int depth, int shallow_flag, int not_shallow_flag);
+struct commit_list *get_shallow_commits_by_rev_list(
+		int ac, const char **av, int shallow_flag, int not_shallow_flag);
+int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
+			  const struct oid_array *extra);
+
+void setup_alternate_shallow(struct shallow_lock *shallow_lock,
+			     const char **alternate_shallow_file,
+			     const struct oid_array *extra);
+
+const char *setup_temporary_shallow(const struct oid_array *extra);
+
+void advertise_shallow_grafts(int);
+
+#define PRUNE_SHOW_ONLY 1
+#define PRUNE_QUICK 2
+void prune_shallow(unsigned options);
+
+/*
+ * Initialize with prepare_shallow_info() or zero-initialize (equivalent to
+ * prepare_shallow_info with a NULL oid_array).
+ */
+struct shallow_info {
+	struct oid_array *shallow;
+	int *ours, nr_ours;
+	int *theirs, nr_theirs;
+	struct oid_array *ref;
+
+	/* for receive-pack */
+	uint32_t **used_shallow;
+	int *need_reachability_test;
+	int *reachable;
+	int *shallow_ref;
+	struct commit **commits;
+	int nr_commits;
+};
+
+void prepare_shallow_info(struct shallow_info *, struct oid_array *);
+void clear_shallow_info(struct shallow_info *);
+void remove_nonexistent_theirs_shallow(struct shallow_info *);
+void assign_shallow_commits_to_refs(struct shallow_info *info,
+				    uint32_t **used,
+				    int *ref_status);
+int delayed_reachability_test(struct shallow_info *si, int c);
+
+extern struct trace_key trace_shallow;
+
+#endif /* SHALLOW_H */
diff --git a/upload-pack.c b/upload-pack.c
index 902d0ad5e1..613a960624 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -26,6 +26,7 @@
 #include "serve.h"
 #include "commit-graph.h"
 #include "commit-reach.h"
+#include "shallow.h"
 
 /* Remember to update object flag allocation in object.h */
 #define THEY_HAVE	(1u << 11)
