diff --git a/builtin/checkout--worker.c b/builtin/checkout--worker.c

index fb9fd13b73..61ba39402a 100644

--- builtin/checkout--worker.c

+++ builtin/checkout--worker.c

@@ -9,7 +9,7 @@ static void packet_to_pc_item(const char *buffer, int len,

 			      struct parallel_checkout_item *pc_item)

 {

 	const struct pc_item_fixed_portion *fixed_portion;

-	const char *variant;

+	const char *variant, *ident_action;

 	char *encoding;

 	if (len < sizeof(struct pc_item_fixed_portion))

@@ -19,7 +19,8 @@ static void packet_to_pc_item(const char *buffer, int len,

 	fixed_portion = (struct pc_item_fixed_portion *)buffer;

 	if (len - sizeof(struct pc_item_fixed_portion) !=

-		fixed_portion->name_len + fixed_portion->working_tree_encoding_len)

+		fixed_portion->name_len + fixed_portion->working_tree_encoding_len +

+		fixed_portion->ident_action_len)

 		BUG("checkout worker received corrupted item");

 	variant = buffer + sizeof(struct pc_item_fixed_portion);

@@ -43,11 +44,21 @@ static void packet_to_pc_item(const char *buffer, int len,

 	pc_item->ce->ce_namelen = fixed_portion->name_len;

 	pc_item->ce->ce_mode = fixed_portion->ce_mode;

 	memcpy(pc_item->ce->name, variant, pc_item->ce->ce_namelen);

+	variant += pc_item->ce->ce_namelen;

 	oidcpy(&pc_item->ce->oid, &fixed_portion->oid);

+	if (fixed_portion->ident_action_len) {

+		ident_action = xmemdupz(variant,

+					fixed_portion->ident_action_len);

+		variant += fixed_portion->ident_action_len;

+	} else {

+		ident_action = NULL;

+	}

+

 	pc_item->id = fixed_portion->id;

 	pc_item->ca.crlf_action = fixed_portion->crlf_action;

-	pc_item->ca.ident = fixed_portion->ident;

+	pc_item->ca.ident_action.id = ident_action;

+	pc_item->ca.ident_action.id_len = fixed_portion->ident_action_len;

 	pc_item->ca.working_tree_encoding = encoding;

 }

--- convert.c.orig	2021-06-06 05:13:45.000000000 -0700

+++ convert.c	2021-08-20 11:05:22.792030000 -0700

@@ -1054,7 +1054,12 @@

 	return 0;

 }

-static int count_ident(const char *cp, unsigned long size)

+#define ID_STR "Id"

+

+#define GIT_MAX_IDENT_LEN 255

+

+static int count_ident(const char *cp, unsigned long size,

+		       const struct ident_action *idact)

 {

 	/*

 	 * "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"

@@ -1067,13 +1072,13 @@

 		size--;

 		if (ch != '$')

 			continue;

-		if (size < 3)

+		if (size < idact->id_len + 1)

 			break;

-		if (memcmp("Id", cp, 2))

+		if (memcmp(idact->id, cp, idact->id_len))

 			continue;

-		ch = cp[2];

-		cp += 3;

-		size -= 3;

+		ch = cp[idact->id_len];

+		cp += idact->id_len + 1;

+		size -= idact->id_len + 1;

 		if (ch == '$')

 			cnt++; /* $Id$ */

 		if (ch != ':')

@@ -1097,11 +1102,11 @@

 }

 static int ident_to_git(const char *src, size_t len,

-			struct strbuf *buf, int ident)

+			struct strbuf *buf, const struct ident_action *idact)

 {

 	char *dst, *dollar;

-	if (!ident || (src && !count_ident(src, len)))

+	if (!idact->id || (src && !count_ident(src, len, idact)))

 		return 0;

 	if (!buf)

@@ -1120,17 +1125,18 @@

 		len -= dollar + 1 - src;

 		src  = dollar + 1;

-		if (len > 3 && !memcmp(src, "Id:", 3)) {

-			dollar = memchr(src + 3, '$', len - 3);

+		if (len > idact->id_len + 1 && !memcmp(src, idact->id, idact->id_len) && src[idact->id_len + 1] == ':') {

+			dollar = memchr(src + idact->id_len + 1, '$', len - (idact->id_len + 1));

 			if (!dollar)

 				break;

-			if (memchr(src + 3, '\n', dollar - src - 3)) {

+			if (memchr(src + idact->id_len + 1, '\n', dollar - src - (idact->id_len + 1))) {

 				/* Line break before the next dollar. */

 				continue;

 			}

-			memcpy(dst, "Id$", 3);

-			dst += 3;

+			memcpy(dst, idact->id, idact->id_len);

+			dst[idact->id_len] = '$';

+			dst += idact->id_len + 1;

 			len -= dollar + 1 - src;

 			src  = dollar + 1;

 		}

@@ -1141,16 +1147,16 @@

 }

 static int ident_to_worktree(const char *src, size_t len,

-			     struct strbuf *buf, int ident)

+			     struct strbuf *buf, const struct ident_action *idact)

 {

 	struct object_id oid;

 	char *to_free = NULL, *dollar, *spc;

 	int cnt;

-	if (!ident)

+	if (!idact->id)

 		return 0;

-	cnt = count_ident(src, len);

+	cnt = count_ident(src, len, idact);

 	if (!cnt)

 		return 0;

@@ -1159,7 +1165,7 @@

 		to_free = strbuf_detach(buf, NULL);

 	hash_object_file(the_hash_algo, src, len, "blob", &oid);

-	strbuf_grow(buf, len + cnt * (the_hash_algo->hexsz + 3));

+	strbuf_grow(buf, len + cnt * (the_hash_algo->hexsz + idact->id_len + 1));

 	for (;;) {

 		/* step 1: run to the next '$' */

 		dollar = memchr(src, '$', len);

@@ -1170,14 +1176,14 @@

 		src  = dollar + 1;

 		/* step 2: does it looks like a bit like Id:xxx$ or Id$ ? */

-		if (len < 3 || memcmp("Id", src, 2))

+		if (len < idact->id_len + 1 || memcmp(idact->id, src, idact->id_len))

 			continue;

 		/* step 3: skip over Id$ or Id:xxxxx$ */

-		if (src[2] == '$') {

-			src += 3;

-			len -= 3;

-		} else if (src[2] == ':') {

+		if (src[idact->id_len] == '$') {

+			src += idact->id_len + 1;

+			len -= idact->id_len + 1;

+		} else if (src[idact->id_len] == ':') {

 			/*

 			 * It's possible that an expanded Id has crept its way into the

 			 * repository, we cope with that by stripping the expansion out.

@@ -1185,18 +1191,18 @@

 			 * on checkout, which won't go away by stash, but let's keep it

 			 * for git-style ids.

 			 */

-			dollar = memchr(src + 3, '$', len - 3);

+			dollar = memchr(src + idact->id_len + 1, '$', len - (idact->id_len + 1));

 			if (!dollar) {

 				/* incomplete keyword, no more '$', so just quit the loop */

 				break;

 			}

-			if (memchr(src + 3, '\n', dollar - src - 3)) {

+			if (memchr(src + idact->id_len + 1, '\n', dollar - src - (idact->id_len + 1))) {

 				/* Line break before the next dollar. */

 				continue;

 			}

-			spc = memchr(src + 4, ' ', dollar - src - 4);

+			spc = memchr(src + idact->id_len + 2, ' ', dollar - src - (idact->id_len + 2));

 			if (spc && spc < dollar-1) {

 				/* There are spaces in unexpected places.

 				 * This is probably an id from some other

@@ -1213,7 +1219,8 @@

 		}

 		/* step 4: substitute */

-		strbuf_addstr(buf, "Id: ");

+		strbuf_addstr(buf, idact->id);

+		strbuf_addstr(buf, ": ");

 		strbuf_addstr(buf, oid_to_hex(&oid));

 		strbuf_addstr(buf, " $");

 	}

@@ -1284,11 +1291,21 @@

 	return NULL;

 }

-static int git_path_check_ident(struct attr_check_item *check)

+static struct ident_action git_path_check_ident(struct attr_check_item *check)

 {

+	struct ident_action idact = {.id = NULL, .id_len = 0};

 	const char *value = check->value;

-	return !!ATTR_TRUE(value);

+	if (!ATTR_UNSET(value) && !ATTR_FALSE(value)) {

+		if (ATTR_TRUE(value))

+			idact.id = ID_STR;

+		else

+			idact.id = value;

+		idact.id_len = strlen(idact.id);

+		if (idact.id_len > GIT_MAX_IDENT_LEN)

+			die(_("ident value length exceeds GIT_MAX_IDENT_LEN"));

+	}

+	return idact;

 }

 static struct attr_check *check;

@@ -1311,7 +1328,7 @@

 	ca->crlf_action = git_path_check_crlf(ccheck + 4);

 	if (ca->crlf_action == CRLF_UNDEFINED)

 		ca->crlf_action = git_path_check_crlf(ccheck + 0);

-	ca->ident = git_path_check_ident(ccheck + 1);

+	ca->ident_action = git_path_check_ident(ccheck + 1);

 	ca->drv = git_path_check_convert(ccheck + 2);

 	if (ca->crlf_action != CRLF_BINARY) {

 		enum eol eol_attr = git_path_check_eol(ccheck + 3);

@@ -1431,7 +1448,7 @@

 			len = dst->len;

 		}

 	}

-	return ret | ident_to_git(src, len, dst, ca.ident);

+	return ret | ident_to_git(src, len, dst, &ca.ident_action);

 }

 void convert_to_git_filter_fd(struct index_state *istate,

@@ -1448,7 +1465,7 @@

 	encode_to_git(path, dst->buf, dst->len, dst, ca.working_tree_encoding, conv_flags);

 	crlf_to_git(istate, path, dst->buf, dst->len, dst, ca.crlf_action, conv_flags);

-	ident_to_git(dst->buf, dst->len, dst, ca.ident);

+	ident_to_git(dst->buf, dst->len, dst, &ca.ident_action);

 }

 static int convert_to_working_tree_ca_internal(const struct conv_attrs *ca,

@@ -1460,7 +1477,7 @@

 {

 	int ret = 0, ret_filter = 0;

-	ret |= ident_to_worktree(src, len, dst, ca->ident);

+	ret |= ident_to_worktree(src, len, dst, &(ca->ident_action));

 	if (ret) {

 		src = dst->buf;

 		len = dst->len;

@@ -1808,7 +1825,8 @@

 	struct stream_filter filter;

 	struct strbuf left;

 	int state;

-	char ident[GIT_MAX_HEXSZ + 5]; /* ": x40 $" */

+	const struct ident_action *idact;

+	char ident[GIT_MAX_HEXSZ + GIT_MAX_IDENT_LEN + 3]; /* ": x40 $" */

 };

 static int is_foreign_ident(const char *str)

@@ -1845,13 +1863,16 @@

 			   char *output, size_t *osize_p)

 {

 	struct ident_filter *ident = (struct ident_filter *)filter;

-	static const char head[] = "$Id";

+	const struct ident_action *idact = ident->idact;

 	if (!input) {

 		/* drain upon eof */

 		switch (ident->state) {

 		default:

-			strbuf_add(&ident->left, head, ident->state);

+			if (ident->state > 0)

+				strbuf_addch(&ident->left, '$');

+			if (ident->state > 1)

+				strbuf_add(&ident->left, idact->id, ident->state - 1);

 			/* fallthrough */

 		case IDENT_SKIPPING:

 			/* fallthrough */

@@ -1883,22 +1904,26 @@

 			if (ch != '\n' && ch != '$')

 				continue;

 			if (ch == '$' && !is_foreign_ident(ident->left.buf)) {

-				strbuf_setlen(&ident->left, sizeof(head) - 1);

+				strbuf_setlen(&ident->left, idact->id_len + 1);

 				strbuf_addstr(&ident->left, ident->ident);

 			}

 			ident->state = IDENT_DRAINING;

 			continue;

 		}

-		if (ident->state < sizeof(head) &&

-		    head[ident->state] == ch) {

+		if ((ident->state == 0 && ch == '$') ||

+		    (ident->state > 0 && ident->state < idact->id_len + 1 &&

+		     idact->id[ident->state - 1] == ch)) {

 			ident->state++;

 			continue;

 		}

-		if (ident->state)

-			strbuf_add(&ident->left, head, ident->state);

-		if (ident->state == sizeof(head) - 1) {

+		if (ident->state) {

+			strbuf_addch(&ident->left, '$');

+			if (ident->state > 1)

+				strbuf_add(&ident->left, idact->id, ident->state - 1);

+		}

+		if (ident->state == idact->id_len + 1) {

 			if (ch != ':' && ch != '$') {

 				strbuf_addch(&ident->left, ch);

 				ident->state = 0;

@@ -1933,7 +1958,7 @@

 	ident_free_fn,

 };

-static struct stream_filter *ident_filter(const struct object_id *oid)

+static struct stream_filter *ident_filter(const struct object_id *oid, const struct ident_action *idact)

 {

 	struct ident_filter *ident = xmalloc(sizeof(*ident));

@@ -1942,6 +1967,7 @@

 	strbuf_init(&ident->left, 0);

 	ident->filter.vtbl = &ident_vtbl;

 	ident->state = 0;

+	ident->idact = idact;

 	return (struct stream_filter *)ident;

 }

@@ -1961,8 +1987,8 @@

 	if (classify_conv_attrs(ca) != CA_CLASS_STREAMABLE)

 		return NULL;

-	if (ca->ident)

-		filter = ident_filter(oid);

+	if (ca->ident_action.id)

+		filter = ident_filter(oid, &(ca->ident_action));

 	if (output_eol(ca->crlf_action) == EOL_CRLF)

 		filter = cascade_filter(filter, lf_to_crlf_filter());

--- convert.h	2021/08/20 18:01:30	1.1

+++ convert.h	2021/08/20 18:03:07

@@ -76,11 +76,16 @@

 struct convert_driver;

+struct ident_action {

+	const char *id;

+	int id_len;

+};

+

 struct conv_attrs {

 	struct convert_driver *drv;

 	enum convert_crlf_action attr_action; /* What attr says */

 	enum convert_crlf_action crlf_action; /* When no attr is set, use core.autocrlf */

-	int ident;

+	struct ident_action ident_action; /* What ident says */

 	const char *working_tree_encoding; /* Supported encoding or default encoding if NULL */

 };

--- parallel-checkout.c.orig	2021-06-06 05:13:45.000000000 -0700

+++ parallel-checkout.c	2021-08-21 15:01:06.622636000 -0700

@@ -403,13 +403,15 @@

 	size_t name_len = pc_item->ce->ce_namelen;

 	size_t working_tree_encoding_len = working_tree_encoding ?

 					   strlen(working_tree_encoding) : 0;

+	const char *ident_action_id = pc_item->ca.ident_action.id;

+	size_t ident_action_len = pc_item->ca.ident_action.id_len;

 	/*

 	 * Any changes in the calculation of the message size must also be made

 	 * in is_eligible_for_parallel_checkout().

 	 */

 	len_data = sizeof(struct pc_item_fixed_portion) + name_len +

-		   working_tree_encoding_len;

+		   working_tree_encoding_len + ident_action_len;

 	data = xcalloc(1, len_data);

@@ -417,7 +419,7 @@

 	fixed_portion->id = pc_item->id;

 	fixed_portion->ce_mode = pc_item->ce->ce_mode;

 	fixed_portion->crlf_action = pc_item->ca.crlf_action;

-	fixed_portion->ident = pc_item->ca.ident;

+	fixed_portion->ident_action_len = ident_action_len;

 	fixed_portion->name_len = name_len;

 	fixed_portion->working_tree_encoding_len = working_tree_encoding_len;

 	/*

@@ -435,6 +437,11 @@

 		variant += working_tree_encoding_len;

 	}

 	memcpy(variant, pc_item->ce->name, name_len);

+	variant += name_len;

+	if (ident_action_len) {

+		memcpy(variant, ident_action_id, ident_action_len);

+		variant += ident_action_len;

+	}

 	packet_write(fd, data, len_data);

--- parallel-checkout.h	2021/08/20 18:16:10	1.1

+++ parallel-checkout.h	2021/08/20 18:21:18

@@ -76,9 +76,9 @@

 /*

  * The fixed-size portion of `struct parallel_checkout_item` that is sent to the

- * workers. Following this will be 2 strings: ca.working_tree_encoding and

- * ce.name; These are NOT null terminated, since we have the size in the fixed

- * portion.

+ * workers. Following this will be 3 strings: ca.working_tree_encoding, ca.name

+ * and ca.ident_action.id; These are NOT null terminated, since we have the size

+ * in the fixed portion.

  *

  * Note that not all fields of conv_attrs and cache_entry are passed, only the

  * ones that will be required by the workers to smudge and write the entry.

@@ -88,7 +88,7 @@

 	struct object_id oid;

 	unsigned int ce_mode;

 	enum convert_crlf_action crlf_action;

-	int ident;

+	size_t ident_action_len;

 	size_t working_tree_encoding_len;

 	size_t name_len;

 };