diff --git a/Documentation/git-index-pack.txt b/Documentation/git-index-pack.txt
index 71ce557276..9fa4847d56 100644
--- a/Documentation/git-index-pack.txt
+++ b/Documentation/git-index-pack.txt
@@ -8,7 +8,8 @@ git-index-pack - Build pack index file for an existing packed archive
 
 SYNOPSIS
 --------
-'git-index-pack' [-o <index-file>] <pack-file>
+'git-index-pack' [-v] [-o <index-file>] <pack-file>
+'git-index-pack' --stdin [--fix-thin] [-v] [-o <index-file>] [<pack-file>]
 
 
 DESCRIPTION
@@ -21,6 +22,9 @@ objects/pack/ directory of a git repository.
 
 OPTIONS
 -------
+-v::
+	Be verbose about what is going on, including progress status.
+
 -o <index-file>::
 	Write the generated pack index into the specified
 	file.  Without this option the name of pack index
@@ -29,6 +33,23 @@ OPTIONS
 	fails if the name of packed archive does not end
 	with .pack).
 
+--stdin::
+	When this flag is provided, the pack is read from stdin
+	instead and a copy is then written to <pack-file>. If
+	<pack-file> is not specified, the pack is written to
+	objects/pack/ directory of the current git repository with
+	a default name determined from the pack content.
+
+--fix-thin::
+	It is possible for gitlink:git-pack-objects[1] to build
+	"thin" pack, which records objects in deltified form based on
+	objects not included in the pack to reduce network traffic.
+	Those objects are expected to be present on the receiving end
+	and they must be included in the pack for that pack to be self
+	contained and indexable. Without this option any attempt to
+	index a thin pack will fail. This option only makes sense in
+	conjonction with --stdin.
+
 
 Author
 ------
diff --git a/fetch-clone.c b/fetch-clone.c
index 76b99afcdb..96cdab43c9 100644
--- a/fetch-clone.c
+++ b/fetch-clone.c
@@ -3,97 +3,6 @@
 #include "pkt-line.h"
 #include "sideband.h"
 #include <sys/wait.h>
-#include <sys/time.h>
-
-static int finish_pack(const char *pack_tmp_name, const char *me)
-{
-	int pipe_fd[2];
-	pid_t pid;
-	char idx[PATH_MAX];
-	char final[PATH_MAX];
-	char hash[41];
-	unsigned char sha1[20];
-	char *cp;
-	int err = 0;
-
-	if (pipe(pipe_fd) < 0)
-		die("%s: unable to set up pipe", me);
-
-	strcpy(idx, pack_tmp_name); /* ".git/objects/pack-XXXXXX" */
-	cp = strrchr(idx, '/');
-	memcpy(cp, "/pidx", 5);
-
-	pid = fork();
-	if (pid < 0)
-		die("%s: unable to fork off git-index-pack", me);
-	if (!pid) {
-		close(0);
-		dup2(pipe_fd[1], 1);
-		close(pipe_fd[0]);
-		close(pipe_fd[1]);
-		execl_git_cmd("index-pack", "-o", idx, pack_tmp_name, NULL);
-		error("cannot exec git-index-pack <%s> <%s>",
-		      idx, pack_tmp_name);
-		exit(1);
-	}
-	close(pipe_fd[1]);
-	if (read(pipe_fd[0], hash, 40) != 40) {
-		error("%s: unable to read from git-index-pack", me);
-		err = 1;
-	}
-	close(pipe_fd[0]);
-
-	for (;;) {
-		int status, code;
-
-		if (waitpid(pid, &status, 0) < 0) {
-			if (errno == EINTR)
-				continue;
-			error("waitpid failed (%s)", strerror(errno));
-			goto error_die;
-		}
-		if (WIFSIGNALED(status)) {
-			int sig = WTERMSIG(status);
-			error("git-index-pack died of signal %d", sig);
-			goto error_die;
-		}
-		if (!WIFEXITED(status)) {
-			error("git-index-pack died of unnatural causes %d",
-			      status);
-			goto error_die;
-		}
-		code = WEXITSTATUS(status);
-		if (code) {
-			error("git-index-pack died with error code %d", code);
-			goto error_die;
-		}
-		if (err)
-			goto error_die;
-		break;
-	}
-	hash[40] = 0;
-	if (get_sha1_hex(hash, sha1)) {
-		error("git-index-pack reported nonsense '%s'", hash);
-		goto error_die;
-	}
-	/* Now we have pack in pack_tmp_name[], and
-	 * idx in idx[]; rename them to their final names.
-	 */
-	snprintf(final, sizeof(final),
-		 "%s/pack/pack-%s.pack", get_object_directory(), hash);
-	move_temp_to_file(pack_tmp_name, final);
-	chmod(final, 0444);
-	snprintf(final, sizeof(final),
-		 "%s/pack/pack-%s.idx", get_object_directory(), hash);
-	move_temp_to_file(idx, final);
-	chmod(final, 0444);
-	return 0;
-
- error_die:
-	unlink(idx);
-	unlink(pack_tmp_name);
-	exit(1);
-}
 
 static pid_t setup_sideband(int sideband, const char *me, int fd[2], int xd[2])
 {
@@ -128,7 +37,7 @@ static pid_t setup_sideband(int sideband, const char *me, int fd[2], int xd[2])
 	return side_pid;
 }
 
-int receive_unpack_pack(int xd[2], const char *me, int quiet, int sideband)
+static int get_pack(int xd[2], const char *me, int sideband, const char **argv)
 {
 	int status;
 	pid_t pid, side_pid;
@@ -142,135 +51,37 @@ int receive_unpack_pack(int xd[2], const char *me, int quiet, int sideband)
 		dup2(fd[0], 0);
 		close(fd[0]);
 		close(fd[1]);
-		execl_git_cmd("unpack-objects", quiet ? "-q" : NULL, NULL);
-		die("git-unpack-objects exec failed");
+		execv_git_cmd(argv);
+		die("%s exec failed", argv[0]);
 	}
 	close(fd[0]);
 	close(fd[1]);
 	while (waitpid(pid, &status, 0) < 0) {
 		if (errno != EINTR)
-			die("waiting for git-unpack-objects: %s",
-			    strerror(errno));
+			die("waiting for %s: %s", argv[0], strerror(errno));
 	}
 	if (WIFEXITED(status)) {
 		int code = WEXITSTATUS(status);
 		if (code)
-			die("git-unpack-objects died with error code %d",
-			    code);
+			die("%s died with error code %d", argv[0], code);
 		return 0;
 	}
 	if (WIFSIGNALED(status)) {
 		int sig = WTERMSIG(status);
-		die("git-unpack-objects died of signal %d", sig);
+		die("%s died of signal %d", argv[0], sig);
 	}
-	die("git-unpack-objects died of unnatural causes %d", status);
+	die("%s died of unnatural causes %d", argv[0], status);
 }
 
-/*
- * We average out the download speed over this many "events", where
- * an event is a minimum of about half a second. That way, we get
- * a reasonably stable number.
- */
-#define NR_AVERAGE (4)
-
-/*
- * A "binary msec" is a power-of-two-msec, aka 1/1024th of a second.
- * Keeping the time in that format means that "bytes / msecs" means
- * the same as kB/s (modulo rounding).
- *
- * 1000512 is a magic number (usecs in a second, rounded up by half
- * of 1024, to make "rounding" come out right ;)
- */
-#define usec_to_binarymsec(x) ((int)(x) / (1000512 >> 10))
+int receive_unpack_pack(int xd[2], const char *me, int quiet, int sideband)
+{
+	const char *argv[3] = { "unpack-objects", quiet ? "-q" : NULL, NULL };
+	return get_pack(xd, me, sideband, argv);
+}
 
 int receive_keep_pack(int xd[2], const char *me, int quiet, int sideband)
 {
-	char tmpfile[PATH_MAX];
-	int ofd, ifd, fd[2];
-	unsigned long total;
-	static struct timeval prev_tv;
-	struct average {
-		unsigned long bytes;
-		unsigned long time;
-	} download[NR_AVERAGE] = { {0, 0}, };
-	unsigned long avg_bytes, avg_time;
-	int idx = 0;
-
-	setup_sideband(sideband, me, fd, xd);
-
-	ifd = fd[0];
-	snprintf(tmpfile, sizeof(tmpfile),
-		 "%s/pack/tmp-XXXXXX", get_object_directory());
-	ofd = mkstemp(tmpfile);
-	if (ofd < 0)
-		return error("unable to create temporary file %s", tmpfile);
-
-	gettimeofday(&prev_tv, NULL);
-	total = 0;
-	avg_bytes = 0;
-	avg_time = 0;
-	while (1) {
-		char buf[8192];
-		ssize_t sz, wsz, pos;
-		sz = read(ifd, buf, sizeof(buf));
-		if (sz == 0)
-			break;
-		if (sz < 0) {
-			if (errno != EINTR && errno != EAGAIN) {
-				error("error reading pack (%s)", strerror(errno));
-				close(ofd);
-				unlink(tmpfile);
-				return -1;
-			}
-			sz = 0;
-		}
-		pos = 0;
-		while (pos < sz) {
-			wsz = write(ofd, buf + pos, sz - pos);
-			if (wsz < 0) {
-				error("error writing pack (%s)",
-				      strerror(errno));
-				close(ofd);
-				unlink(tmpfile);
-				return -1;
-			}
-			pos += wsz;
-		}
-		total += sz;
-		if (!quiet) {
-			static unsigned long last;
-			struct timeval tv;
-			unsigned long diff = total - last;
-			/* not really "msecs", but a power-of-two millisec (1/1024th of a sec) */
-			unsigned long msecs;
-
-			gettimeofday(&tv, NULL);
-			msecs = tv.tv_sec - prev_tv.tv_sec;
-			msecs <<= 10;
-			msecs += usec_to_binarymsec(tv.tv_usec - prev_tv.tv_usec);
-
-			if (msecs > 500) {
-				prev_tv = tv;
-				last = total;
-
-				/* Update averages ..*/
-				avg_bytes += diff;
-				avg_time += msecs;
-				avg_bytes -= download[idx].bytes;
-				avg_time -= download[idx].time;
-				download[idx].bytes = diff;
-				download[idx].time = msecs;
-				idx++;
-				if (idx >= NR_AVERAGE)
-					idx = 0;
-
-				fprintf(stderr, "%4lu.%03luMB  (%lu kB/s)      \r",
-					total >> 20,
-					1000*((total >> 10) & 1023)>>10,
-					avg_bytes / avg_time );
-			}
-		}
-	}
-	close(ofd);
-	return finish_pack(tmpfile, me);
+	const char *argv[5] = { "index-pack", "--stdin", "--fix-thin",
+				quiet ? NULL : "-v", NULL };
+	return get_pack(xd, me, sideband, argv);
 }
diff --git a/fetch-pack.c b/fetch-pack.c
index 474d54520e..8720ed42e9 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -518,8 +518,6 @@ int main(int argc, char **argv)
 	}
 	if (!dest)
 		usage(fetch_pack_usage);
-	if (keep_pack)
-		use_thin_pack = 0;
 	pid = git_connect(fd, dest, exec);
 	if (pid < 0)
 		return 1;
diff --git a/index-pack.c b/index-pack.c
index e33f60524f..866a054056 100644
--- a/index-pack.c
+++ b/index-pack.c
@@ -6,9 +6,11 @@
 #include "commit.h"
 #include "tag.h"
 #include "tree.h"
+#include <sys/time.h>
+#include <signal.h>
 
 static const char index_pack_usage[] =
-"git-index-pack [-o index-file] pack-file";
+"git-index-pack [-v] [-o <index-file>] { <pack-file> | --stdin [--fix-thin] [<pack-file>] }";
 
 struct object_entry
 {
@@ -33,37 +35,83 @@ union delta_base {
 
 struct delta_entry
 {
-	struct object_entry *obj;
 	union delta_base base;
+	int obj_no;
 };
 
-static const char *pack_name;
 static struct object_entry *objects;
 static struct delta_entry *deltas;
 static int nr_objects;
 static int nr_deltas;
+static int nr_resolved_deltas;
+
+static int from_stdin;
+static int verbose;
+
+static volatile sig_atomic_t progress_update;
+
+static void progress_interval(int signum)
+{
+	progress_update = 1;
+}
+
+static void setup_progress_signal(void)
+{
+	struct sigaction sa;
+	struct itimerval v;
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_handler = progress_interval;
+	sigemptyset(&sa.sa_mask);
+	sa.sa_flags = SA_RESTART;
+	sigaction(SIGALRM, &sa, NULL);
+
+	v.it_interval.tv_sec = 1;
+	v.it_interval.tv_usec = 0;
+	v.it_value = v.it_interval;
+	setitimer(ITIMER_REAL, &v, NULL);
+
+}
+
+static unsigned display_progress(unsigned n, unsigned total, unsigned last_pc)
+{
+	unsigned percent = n * 100 / total;
+	if (percent != last_pc || progress_update) {
+		fprintf(stderr, "%4u%% (%u/%u) done\r", percent, n, total);
+		progress_update = 0;
+	}
+	return percent;
+}
 
 /* We always read in 4kB chunks. */
 static unsigned char input_buffer[4096];
 static unsigned long input_offset, input_len, consumed_bytes;
 static SHA_CTX input_ctx;
-static int input_fd;
+static int input_fd, output_fd, mmap_fd;
+
+/* Discard current buffer used content. */
+static void flush()
+{
+	if (input_offset) {
+		if (output_fd >= 0)
+			write_or_die(output_fd, input_buffer, input_offset);
+		SHA1_Update(&input_ctx, input_buffer, input_offset);
+		memcpy(input_buffer, input_buffer + input_offset, input_len);
+		input_offset = 0;
+	}
+}
 
 /*
  * Make sure at least "min" bytes are available in the buffer, and
  * return the pointer to the buffer.
  */
-static void * fill(int min)
+static void *fill(int min)
 {
 	if (min <= input_len)
 		return input_buffer + input_offset;
 	if (min > sizeof(input_buffer))
 		die("cannot fill %d bytes", min);
-	if (input_offset) {
-		SHA1_Update(&input_ctx, input_buffer, input_offset);
-		memcpy(input_buffer, input_buffer + input_offset, input_len);
-		input_offset = 0;
-	}
+	flush();
 	do {
 		int ret = xread(input_fd, input_buffer + input_len,
 				sizeof(input_buffer) - input_len);
@@ -86,13 +134,31 @@ static void use(int bytes)
 	consumed_bytes += bytes;
 }
 
-static void open_pack_file(void)
+static const char *open_pack_file(const char *pack_name)
 {
-	input_fd = open(pack_name, O_RDONLY);
-	if (input_fd < 0)
-		die("cannot open packfile '%s': %s", pack_name,
-		    strerror(errno));
+	if (from_stdin) {
+		input_fd = 0;
+		if (!pack_name) {
+			static char tmpfile[PATH_MAX];
+			snprintf(tmpfile, sizeof(tmpfile),
+				 "%s/pack_XXXXXX", get_object_directory());
+			output_fd = mkstemp(tmpfile);
+			pack_name = xstrdup(tmpfile);
+		} else
+			output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600);
+		if (output_fd < 0)
+			die("unable to create %s: %s\n", pack_name, strerror(errno));
+		mmap_fd = output_fd;
+	} else {
+		input_fd = open(pack_name, O_RDONLY);
+		if (input_fd < 0)
+			die("cannot open packfile '%s': %s",
+			    pack_name, strerror(errno));
+		output_fd = -1;
+		mmap_fd = input_fd;
+	}
 	SHA1_Init(&input_ctx);
+	return pack_name;
 }
 
 static void parse_pack_header(void)
@@ -101,14 +167,12 @@ static void parse_pack_header(void)
 
 	/* Header consistency check */
 	if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
-		die("packfile '%s' signature mismatch", pack_name);
+		die("pack signature mismatch");
 	if (!pack_version_ok(hdr->hdr_version))
-		die("packfile '%s' version %d unsupported",
-		    pack_name, ntohl(hdr->hdr_version));
+		die("pack version %d unsupported", ntohl(hdr->hdr_version));
 
 	nr_objects = ntohl(hdr->hdr_entries);
 	use(sizeof(struct pack_header));
-	/*fprintf(stderr, "Indexing %d objects\n", nr_objects);*/
 }
 
 static void bad_object(unsigned long offset, const char *format,
@@ -122,8 +186,7 @@ static void bad_object(unsigned long offset, const char *format, ...)
 	va_start(params, format);
 	vsnprintf(buf, sizeof(buf), format, params);
 	va_end(params);
-	die("packfile '%s': bad object at offset %lu: %s",
-	    pack_name, offset, buf);
+	die("pack has bad object at offset %lu: %s", offset, buf);
 }
 
 static void *unpack_entry_data(unsigned long offset, unsigned long size)
@@ -212,7 +275,7 @@ static void *unpack_raw_entry(struct object_entry *obj, union delta_base *delta_
 	return unpack_entry_data(obj->offset, obj->size);
 }
 
-static void * get_data_from_pack(struct object_entry *obj)
+static void *get_data_from_pack(struct object_entry *obj)
 {
 	unsigned long from = obj[0].offset + obj[0].hdr_size;
 	unsigned long len = obj[1].offset - from;
@@ -222,9 +285,9 @@ static void * get_data_from_pack(struct object_entry *obj)
 	int st;
 
 	map = mmap(NULL, len + pg_offset, PROT_READ, MAP_PRIVATE,
-		   input_fd, from - pg_offset);
+		   mmap_fd, from - pg_offset);
 	if (map == MAP_FAILED)
-		die("cannot mmap packfile '%s': %s", pack_name, strerror(errno));
+		die("cannot mmap pack file: %s", strerror(errno));
 	data = xmalloc(obj->size);
 	memset(&stream, 0, sizeof(stream));
 	stream.next_out = data;
@@ -261,8 +324,8 @@ static int find_delta(const union delta_base *base)
         return -first-1;
 }
 
-static int find_delta_childs(const union delta_base *base,
-			     int *first_index, int *last_index)
+static int find_delta_children(const union delta_base *base,
+			       int *first_index, int *last_index)
 {
 	int first = find_delta(base);
 	int last = first;
@@ -304,10 +367,9 @@ static void sha1_object(const void *data, unsigned long size,
 	SHA1_Final(sha1, &ctx);
 }
 
-static void resolve_delta(struct delta_entry *delta, void *base_data,
+static void resolve_delta(struct object_entry *delta_obj, void *base_data,
 			  unsigned long base_size, enum object_type type)
 {
-	struct object_entry *obj = delta->obj;
 	void *delta_data;
 	unsigned long delta_size;
 	void *result;
@@ -315,29 +377,34 @@ static void resolve_delta(struct delta_entry *delta, void *base_data,
 	union delta_base delta_base;
 	int j, first, last;
 
-	obj->real_type = type;
-	delta_data = get_data_from_pack(obj);
-	delta_size = obj->size;
+	delta_obj->real_type = type;
+	delta_data = get_data_from_pack(delta_obj);
+	delta_size = delta_obj->size;
 	result = patch_delta(base_data, base_size, delta_data, delta_size,
 			     &result_size);
 	free(delta_data);
 	if (!result)
-		bad_object(obj->offset, "failed to apply delta");
-	sha1_object(result, result_size, type, obj->sha1);
+		bad_object(delta_obj->offset, "failed to apply delta");
+	sha1_object(result, result_size, type, delta_obj->sha1);
+	nr_resolved_deltas++;
 
-	hashcpy(delta_base.sha1, obj->sha1);
-	if (!find_delta_childs(&delta_base, &first, &last)) {
-		for (j = first; j <= last; j++)
-			if (deltas[j].obj->type == OBJ_REF_DELTA)
-				resolve_delta(&deltas[j], result, result_size, type);
+	hashcpy(delta_base.sha1, delta_obj->sha1);
+	if (!find_delta_children(&delta_base, &first, &last)) {
+		for (j = first; j <= last; j++) {
+			struct object_entry *child = objects + deltas[j].obj_no;
+			if (child->real_type == OBJ_REF_DELTA)
+				resolve_delta(child, result, result_size, type);
+		}
 	}
 
 	memset(&delta_base, 0, sizeof(delta_base));
-	delta_base.offset = obj->offset;
-	if (!find_delta_childs(&delta_base, &first, &last)) {
-		for (j = first; j <= last; j++)
-			if (deltas[j].obj->type == OBJ_OFS_DELTA)
-				resolve_delta(&deltas[j], result, result_size, type);
+	delta_base.offset = delta_obj->offset;
+	if (!find_delta_children(&delta_base, &first, &last)) {
+		for (j = first; j <= last; j++) {
+			struct object_entry *child = objects + deltas[j].obj_no;
+			if (child->real_type == OBJ_OFS_DELTA)
+				resolve_delta(child, result, result_size, type);
+		}
 	}
 
 	free(result);
@@ -353,7 +420,7 @@ static int compare_delta_entry(const void *a, const void *b)
 /* Parse all objects and return the pack content SHA1 hash */
 static void parse_pack_objects(unsigned char *sha1)
 {
-	int i;
+	int i, percent = -1;
 	struct delta_entry *delta = deltas;
 	void *data;
 	struct stat st;
@@ -362,34 +429,43 @@ static void parse_pack_objects(unsigned char *sha1)
 	 * First pass:
 	 * - find locations of all objects;
 	 * - calculate SHA1 of all non-delta objects;
-	 * - remember base SHA1 for all deltas.
+	 * - remember base (SHA1 or offset) for all deltas.
 	 */
+	if (verbose)
+		fprintf(stderr, "Indexing %d objects.\n", nr_objects);
 	for (i = 0; i < nr_objects; i++) {
 		struct object_entry *obj = &objects[i];
 		data = unpack_raw_entry(obj, &delta->base);
 		obj->real_type = obj->type;
 		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA) {
 			nr_deltas++;
-			delta->obj = obj;
+			delta->obj_no = i;
 			delta++;
 		} else
 			sha1_object(data, obj->size, obj->type, obj->sha1);
 		free(data);
+		if (verbose)
+			percent = display_progress(i+1, nr_objects, percent);
 	}
 	objects[i].offset = consumed_bytes;
+	if (verbose)
+		fputc('\n', stderr);
 
 	/* Check pack integrity */
-	SHA1_Update(&input_ctx, input_buffer, input_offset);
+	flush();
 	SHA1_Final(sha1, &input_ctx);
 	if (hashcmp(fill(20), sha1))
-		die("packfile '%s' SHA1 mismatch", pack_name);
+		die("pack is corrupted (SHA1 mismatch)");
 	use(20);
 
 	/* If input_fd is a file, we should have reached its end now. */
 	if (fstat(input_fd, &st))
-		die("cannot fstat packfile '%s': %s", pack_name, strerror(errno));
+		die("cannot fstat packfile: %s", strerror(errno));
 	if (S_ISREG(st.st_mode) && st.st_size != consumed_bytes)
-		die("packfile '%s' has junk at the end", pack_name);
+		die("pack has junk at the end");
+
+	if (!nr_deltas)
+		return;
 
 	/* Sort deltas by base SHA1/offset for fast searching */
 	qsort(deltas, nr_deltas, sizeof(struct delta_entry),
@@ -403,6 +479,8 @@ static void parse_pack_objects(unsigned char *sha1)
 	 *   recursively checking if the resulting object is used as a base
 	 *   for some more deltas.
 	 */
+	if (verbose)
+		fprintf(stderr, "Resolving %d deltas.\n", nr_deltas);
 	for (i = 0; i < nr_objects; i++) {
 		struct object_entry *obj = &objects[i];
 		union delta_base base;
@@ -411,32 +489,179 @@ static void parse_pack_objects(unsigned char *sha1)
 		if (obj->type == OBJ_REF_DELTA || obj->type == OBJ_OFS_DELTA)
 			continue;
 		hashcpy(base.sha1, obj->sha1);
-		ref = !find_delta_childs(&base, &ref_first, &ref_last);
+		ref = !find_delta_children(&base, &ref_first, &ref_last);
 		memset(&base, 0, sizeof(base));
 		base.offset = obj->offset;
-		ofs = !find_delta_childs(&base, &ofs_first, &ofs_last);
+		ofs = !find_delta_children(&base, &ofs_first, &ofs_last);
 		if (!ref && !ofs)
 			continue;
 		data = get_data_from_pack(obj);
 		if (ref)
-			for (j = ref_first; j <= ref_last; j++)
-				if (deltas[j].obj->type == OBJ_REF_DELTA)
-					resolve_delta(&deltas[j], data,
+			for (j = ref_first; j <= ref_last; j++) {
+				struct object_entry *child = objects + deltas[j].obj_no;
+				if (child->real_type == OBJ_REF_DELTA)
+					resolve_delta(child, data,
 						      obj->size, obj->type);
+			}
 		if (ofs)
-			for (j = ofs_first; j <= ofs_last; j++)
-				if (deltas[j].obj->type == OBJ_OFS_DELTA)
-					resolve_delta(&deltas[j], data,
+			for (j = ofs_first; j <= ofs_last; j++) {
+				struct object_entry *child = objects + deltas[j].obj_no;
+				if (child->real_type == OBJ_OFS_DELTA)
+					resolve_delta(child, data,
 						      obj->size, obj->type);
+			}
 		free(data);
+		if (verbose)
+			percent = display_progress(nr_resolved_deltas,
+						   nr_deltas, percent);
 	}
+	if (verbose && nr_resolved_deltas == nr_deltas)
+		fputc('\n', stderr);
+}
 
-	/* Check for unresolved deltas */
-	for (i = 0; i < nr_deltas; i++) {
-		if (deltas[i].obj->real_type == OBJ_REF_DELTA ||
-		    deltas[i].obj->real_type == OBJ_OFS_DELTA)
-			die("packfile '%s' has unresolved deltas",  pack_name);
+static int write_compressed(int fd, void *in, unsigned int size)
+{
+	z_stream stream;
+	unsigned long maxsize;
+	void *out;
+
+	memset(&stream, 0, sizeof(stream));
+	deflateInit(&stream, zlib_compression_level);
+	maxsize = deflateBound(&stream, size);
+	out = xmalloc(maxsize);
+
+	/* Compress it */
+	stream.next_in = in;
+	stream.avail_in = size;
+	stream.next_out = out;
+	stream.avail_out = maxsize;
+	while (deflate(&stream, Z_FINISH) == Z_OK);
+	deflateEnd(&stream);
+
+	size = stream.total_out;
+	write_or_die(fd, out, size);
+	free(out);
+	return size;
+}
+
+static void append_obj_to_pack(void *buf,
+			       unsigned long size, enum object_type type)
+{
+	struct object_entry *obj = &objects[nr_objects++];
+	unsigned char header[10];
+	unsigned long s = size;
+	int n = 0;
+	unsigned char c = (type << 4) | (s & 15);
+	s >>= 4;
+	while (s) {
+		header[n++] = c | 0x80;
+		c = s & 0x7f;
+		s >>= 7;
 	}
+	header[n++] = c;
+	write_or_die(output_fd, header, n);
+	obj[1].offset = obj[0].offset + n;
+	obj[1].offset += write_compressed(output_fd, buf, size);
+	sha1_object(buf, size, type, obj->sha1);
+}
+
+static int delta_pos_compare(const void *_a, const void *_b)
+{
+	struct delta_entry *a = *(struct delta_entry **)_a;
+	struct delta_entry *b = *(struct delta_entry **)_b;
+	return a->obj_no - b->obj_no;
+}
+
+static void fix_unresolved_deltas(int nr_unresolved)
+{
+	struct delta_entry **sorted_by_pos;
+	int i, n = 0, percent = -1;
+
+	/*
+	 * Since many unresolved deltas may well be themselves base objects
+	 * for more unresolved deltas, we really want to include the
+	 * smallest number of base objects that would cover as much delta
+	 * as possible by picking the
+	 * trunc deltas first, allowing for other deltas to resolve without
+	 * additional base objects.  Since most base objects are to be found
+	 * before deltas depending on them, a good heuristic is to start
+	 * resolving deltas in the same order as their position in the pack.
+	 */
+	sorted_by_pos = xmalloc(nr_unresolved * sizeof(*sorted_by_pos));
+	for (i = 0; i < nr_deltas; i++) {
+		if (objects[deltas[i].obj_no].real_type != OBJ_REF_DELTA)
+			continue;
+		sorted_by_pos[n++] = &deltas[i];
+	}
+	qsort(sorted_by_pos, n, sizeof(*sorted_by_pos), delta_pos_compare);
+
+	for (i = 0; i < n; i++) {
+		struct delta_entry *d = sorted_by_pos[i];
+		void *data;
+		unsigned long size;
+		char type[10];
+		enum object_type obj_type;
+		int j, first, last;
+
+		if (objects[d->obj_no].real_type != OBJ_REF_DELTA)
+			continue;
+		data = read_sha1_file(d->base.sha1, type, &size);
+		if (!data)
+			continue;
+		if      (!strcmp(type, blob_type))   obj_type = OBJ_BLOB;
+		else if (!strcmp(type, tree_type))   obj_type = OBJ_TREE;
+		else if (!strcmp(type, commit_type)) obj_type = OBJ_COMMIT;
+		else if (!strcmp(type, tag_type))    obj_type = OBJ_TAG;
+		else die("base object %s is of type '%s'",
+			 sha1_to_hex(d->base.sha1), type);
+
+		find_delta_children(&d->base, &first, &last);
+		for (j = first; j <= last; j++) {
+			struct object_entry *child = objects + deltas[j].obj_no;
+			if (child->real_type == OBJ_REF_DELTA)
+				resolve_delta(child, data, size, obj_type);
+		}
+
+		append_obj_to_pack(data, size, obj_type);
+		free(data);
+		if (verbose)
+			percent = display_progress(nr_resolved_deltas,
+						   nr_deltas, percent);
+	}
+	free(sorted_by_pos);
+	if (verbose)
+		fputc('\n', stderr);
+}
+
+static void readjust_pack_header_and_sha1(unsigned char *sha1)
+{
+	struct pack_header hdr;
+	SHA_CTX ctx;
+	int size;
+
+	/* Rewrite pack header with updated object number */
+	if (lseek(output_fd, 0, SEEK_SET) != 0)
+		die("cannot seek back: %s", strerror(errno));
+	if (xread(output_fd, &hdr, sizeof(hdr)) != sizeof(hdr))
+		die("cannot read pack header back: %s", strerror(errno));
+	hdr.hdr_entries = htonl(nr_objects);
+	if (lseek(output_fd, 0, SEEK_SET) != 0)
+		die("cannot seek back: %s", strerror(errno));
+	write_or_die(output_fd, &hdr, sizeof(hdr));
+	if (lseek(output_fd, 0, SEEK_SET) != 0)
+		die("cannot seek back: %s", strerror(errno));
+
+	/* Recompute and store the new pack's SHA1 */
+	SHA1_Init(&ctx);
+	do {
+		unsigned char *buf[4096];
+		size = xread(output_fd, buf, sizeof(buf));
+		if (size < 0)
+			die("cannot read pack data back: %s", strerror(errno));
+		SHA1_Update(&ctx, buf, size);
+	} while (size > 0);
+	SHA1_Final(sha1, &ctx);
+	write_or_die(output_fd, sha1, 20);
 }
 
 static int sha1_compare(const void *_a, const void *_b)
@@ -450,12 +675,12 @@ static int sha1_compare(const void *_a, const void *_b)
  * On entry *sha1 contains the pack content SHA1 hash, on exit it is
  * the SHA1 hash of sorted object names.
  */
-static void write_index_file(const char *index_name, unsigned char *sha1)
+static const char *write_index_file(const char *index_name, unsigned char *sha1)
 {
 	struct sha1file *f;
 	struct object_entry **sorted_by_sha, **list, **last;
 	unsigned int array[256];
-	int i;
+	int i, fd;
 	SHA_CTX ctx;
 
 	if (nr_objects) {
@@ -472,8 +697,19 @@ static void write_index_file(const char *index_name, unsigned char *sha1)
 	else
 		sorted_by_sha = list = last = NULL;
 
-	unlink(index_name);
-	f = sha1create("%s", index_name);
+	if (!index_name) {
+		static char tmpfile[PATH_MAX];
+		snprintf(tmpfile, sizeof(tmpfile),
+			 "%s/index_XXXXXX", get_object_directory());
+		fd = mkstemp(tmpfile);
+		index_name = xstrdup(tmpfile);
+	} else {
+		unlink(index_name);
+		fd = open(index_name, O_CREAT|O_EXCL|O_WRONLY, 0600);
+	}
+	if (fd < 0)
+		die("unable to create %s: %s", index_name, strerror(errno));
+	f = sha1fd(fd, index_name);
 
 	/*
 	 * Write the first-level table (the list is sorted,
@@ -513,12 +749,64 @@ static void write_index_file(const char *index_name, unsigned char *sha1)
 	sha1close(f, NULL, 1);
 	free(sorted_by_sha);
 	SHA1_Final(sha1, &ctx);
+	return index_name;
+}
+
+static void final(const char *final_pack_name, const char *curr_pack_name,
+		  const char *final_index_name, const char *curr_index_name,
+		  unsigned char *sha1)
+{
+	char name[PATH_MAX];
+	int err;
+
+	if (!from_stdin) {
+		close(input_fd);
+	} else {
+		err = close(output_fd);
+		if (err)
+			die("error while closing pack file: %s", strerror(errno));
+		chmod(curr_pack_name, 0444);
+
+		/*
+		 * Let's just mimic git-unpack-objects here and write
+		 * the last part of the buffer to stdout.
+		 */
+		while (input_len) {
+			err = xwrite(1, input_buffer + input_offset, input_len);
+			if (err <= 0)
+				break;
+			input_len -= err;
+			input_offset += err;
+		}
+	}
+
+	if (final_pack_name != curr_pack_name) {
+		if (!final_pack_name) {
+			snprintf(name, sizeof(name), "%s/pack/pack-%s.pack",
+				 get_object_directory(), sha1_to_hex(sha1));
+			final_pack_name = name;
+		}
+		if (move_temp_to_file(curr_pack_name, final_pack_name))
+			die("cannot store pack file");
+	}
+
+	chmod(curr_index_name, 0444);
+	if (final_index_name != curr_index_name) {
+		if (!final_index_name) {
+			snprintf(name, sizeof(name), "%s/pack/pack-%s.idx",
+				 get_object_directory(), sha1_to_hex(sha1));
+			final_index_name = name;
+		}
+		if (move_temp_to_file(curr_index_name, final_index_name))
+			die("cannot store index file");
+	}
 }
 
 int main(int argc, char **argv)
 {
-	int i;
-	char *index_name = NULL;
+	int i, fix_thin_pack = 0;
+	const char *curr_pack, *pack_name = NULL;
+	const char *curr_index, *index_name = NULL;
 	char *index_name_buf = NULL;
 	unsigned char sha1[20];
 
@@ -526,7 +814,13 @@ int main(int argc, char **argv)
 		const char *arg = argv[i];
 
 		if (*arg == '-') {
-			if (!strcmp(arg, "-o")) {
+			if (!strcmp(arg, "--stdin")) {
+				from_stdin = 1;
+			} else if (!strcmp(arg, "--fix-thin")) {
+				fix_thin_pack = 1;
+			} else if (!strcmp(arg, "-v")) {
+				verbose = 1;
+			} else if (!strcmp(arg, "-o")) {
 				if (index_name || (i+1) >= argc)
 					usage(index_pack_usage);
 				index_name = argv[++i];
@@ -540,9 +834,11 @@ int main(int argc, char **argv)
 		pack_name = arg;
 	}
 
-	if (!pack_name)
+	if (!pack_name && !from_stdin)
 		usage(index_pack_usage);
-	if (!index_name) {
+	if (fix_thin_pack && !from_stdin)
+		die("--fix-thin cannot be used without --stdin");
+	if (!index_name && pack_name) {
 		int len = strlen(pack_name);
 		if (!has_extension(pack_name, ".pack"))
 			die("packfile name '%s' does not end with '.pack'",
@@ -553,17 +849,43 @@ int main(int argc, char **argv)
 		index_name = index_name_buf;
 	}
 
-	open_pack_file();
+	curr_pack = open_pack_file(pack_name);
 	parse_pack_header();
-	objects = xcalloc(nr_objects + 1, sizeof(struct object_entry));
-	deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
+	objects = xmalloc((nr_objects + 1) * sizeof(struct object_entry));
+	deltas = xmalloc(nr_objects * sizeof(struct delta_entry));
+	if (verbose)
+		setup_progress_signal();
 	parse_pack_objects(sha1);
+	if (nr_deltas != nr_resolved_deltas) {
+		if (fix_thin_pack) {
+			int nr_unresolved = nr_deltas - nr_resolved_deltas;
+			int nr_objects_initial = nr_objects;
+			if (nr_unresolved <= 0)
+				die("confusion beyond insanity");
+			objects = xrealloc(objects,
+					   (nr_objects + nr_unresolved + 1)
+					   * sizeof(*objects));
+			fix_unresolved_deltas(nr_unresolved);
+			if (verbose)
+				fprintf(stderr, "%d objects were added to complete this thin pack.\n",
+					nr_objects - nr_objects_initial);
+			readjust_pack_header_and_sha1(sha1);
+		}
+		if (nr_deltas != nr_resolved_deltas)
+			die("pack has %d unresolved deltas",
+			    nr_deltas - nr_resolved_deltas);
+	} else {
+		/* Flush remaining pack final 20-byte SHA1. */
+		flush();
+	}
 	free(deltas);
-	write_index_file(index_name, sha1);
+	curr_index = write_index_file(index_name, sha1);
+	final(pack_name, curr_pack, index_name, curr_index, sha1);
 	free(objects);
 	free(index_name_buf);
 
-	printf("%s\n", sha1_to_hex(sha1));
+	if (!from_stdin)
+		printf("%s\n", sha1_to_hex(sha1));
 
 	return 0;
 }