diff --git a/hook.c b/hook.c
index b3de1048bf..5ddd7678d1 100644
--- a/hook.c
+++ b/hook.c
@@ -55,7 +55,7 @@ int hook_exists(struct repository *r, const char *name)
 static int pick_next_hook(struct child_process *cp,
 			  struct strbuf *out UNUSED,
 			  void *pp_cb,
-			  void **pp_task_cb UNUSED)
+			  void **pp_task_cb)
 {
 	struct hook_cb_data *hook_cb = pp_cb;
 	const char *hook_path = hook_cb->hook_path;
@@ -65,11 +65,22 @@ static int pick_next_hook(struct child_process *cp,
 
 	cp->no_stdin = 1;
 	strvec_pushv(&cp->env, hook_cb->options->env.v);
+
+	if (hook_cb->options->path_to_stdin && hook_cb->options->feed_pipe)
+		BUG("options path_to_stdin and feed_pipe are mutually exclusive");
+
 	/* reopen the file for stdin; run_command closes it. */
 	if (hook_cb->options->path_to_stdin) {
 		cp->no_stdin = 0;
 		cp->in = xopen(hook_cb->options->path_to_stdin, O_RDONLY);
 	}
+
+	if (hook_cb->options->feed_pipe) {
+		cp->no_stdin = 0;
+		/* start_command() will allocate a pipe / stdin fd for us */
+		cp->in = -1;
+	}
+
 	cp->stdout_to_stderr = 1;
 	cp->trace2_hook_name = hook_cb->hook_name;
 	cp->dir = hook_cb->options->dir;
@@ -77,6 +88,12 @@ static int pick_next_hook(struct child_process *cp,
 	strvec_push(&cp->args, hook_path);
 	strvec_pushv(&cp->args, hook_cb->options->args.v);
 
+	/*
+	 * Provide per-hook internal state via task_cb for easy access, so
+	 * hook callbacks don't have to go through hook_cb->options.
+	 */
+	*pp_task_cb = hook_cb->options->feed_pipe_cb_data;
+
 	/*
 	 * This pick_next_hook() will be called again, we're only
 	 * running one hook, so indicate that no more work will be
@@ -140,6 +157,7 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 
 		.get_next_task = pick_next_hook,
 		.start_failure = notify_start_failure,
+		.feed_pipe = options->feed_pipe,
 		.task_finished = notify_hook_finished,
 
 		.data = &cb_data,
@@ -148,6 +166,9 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 	if (!options)
 		BUG("a struct run_hooks_opt must be provided to run_hooks");
 
+	if (options->path_to_stdin && options->feed_pipe)
+		BUG("options path_to_stdin and feed_pipe are mutually exclusive");
+
 	if (options->invoked_hook)
 		*options->invoked_hook = 0;
 
diff --git a/hook.h b/hook.h
index 11863fa734..2169d4a6bd 100644
--- a/hook.h
+++ b/hook.h
@@ -1,6 +1,7 @@
 #ifndef HOOK_H
 #define HOOK_H
 #include "strvec.h"
+#include "run-command.h"
 
 struct repository;
 
@@ -37,6 +38,43 @@ struct run_hooks_opt
 	 * Path to file which should be piped to stdin for each hook.
 	 */
 	const char *path_to_stdin;
+
+	/**
+	 * Callback used to incrementally feed a child hook stdin pipe.
+	 *
+	 * Useful especially if a hook consumes large quantities of data
+	 * (e.g. a list of all refs in a client push), so feeding it via
+	 * in-memory strings or slurping to/from files is inefficient.
+	 * While the callback allows piecemeal writing, it can also be
+	 * used for smaller inputs, where it gets called only once.
+	 *
+	 * Add hook callback initalization context to `feed_pipe_ctx`.
+	 * Add hook callback internal state to `feed_pipe_cb_data`.
+	 *
+	 */
+	feed_pipe_fn feed_pipe;
+
+	/**
+	 * Opaque data pointer used to pass context to `feed_pipe_fn`.
+	 *
+	 * It can be accessed via the second callback arg 'pp_cb':
+	 * ((struct hook_cb_data *) pp_cb)->hook_cb->options->feed_pipe_ctx;
+	 *
+	 * The caller is responsible for managing the memory for this data.
+	 * Only useful when using `run_hooks_opt.feed_pipe`, otherwise ignore it.
+	 */
+	void *feed_pipe_ctx;
+
+	/**
+	 * Opaque data pointer used to keep internal state across callback calls.
+	 *
+	 * It can be accessed directly via the third callback arg 'pp_task_cb':
+	 * struct ... *state = pp_task_cb;
+	 *
+	 * The caller is responsible for managing the memory for this data.
+	 * Only useful when using `run_hooks_opt.feed_pipe`, otherwise ignore it.
+	 */
+	void *feed_pipe_cb_data;
 };
 
 #define RUN_HOOKS_OPT_INIT { \