Merge branch 'js/shallow'

* js/shallow:
  fetch-pack: Do not fetch tags for shallow clones.
  get_shallow_commits: Avoid memory leak if a commit has been reached already.
  git-fetch: Reset shallow_depth before auto-following tags.
  upload-pack: Check for NOT_SHALLOW flag before sending a shallow to the client.
  fetch-pack: Properly remove the shallow file when it becomes empty.
  shallow clone: unparse and reparse an unshallowed commit
  Why didn't we mark want_obj as ~UNINTERESTING in the old code?
  Why does it mean we do not have to register shallow if we have one?
  We should make sure that the protocol is still extensible.
  add tests for shallow stuff
  Shallow clone: do not ignore shallowness when following tags
  allow deepening of a shallow repository
  allow cloning a repository "shallowly"
  support fetching into a shallow repository
  upload-pack: no longer call rev-list

9 files changed, 445 insertions, 48 deletions

diff --git a/Makefile b/Makefile
index 775ffaac27..544385f3e3 100644
--- a/Makefile
+++ b/Makefile
@@ -250,8 +250,7 @@ LIB_OBJS = \
 	revision.o pager.o tree-walk.o xdiff-interface.o \
 	write_or_die.o trace.o list-objects.o grep.o \
 	alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS) \
-	color.o wt-status.o archive-zip.o archive-tar.o \
-	utf8.o
+	color.o wt-status.o archive-zip.o archive-tar.o shallow.o utf8.o
 
 BUILTIN_OBJS = \
 	builtin-add.o \
diff --git a/commit.c b/commit.c
index 3167ce62ac..59ea77c577 100644
--- a/commit.c
+++ b/commit.c
@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "tag.h"
 #include "commit.h"
+#include "pkt-line.h"
 
 int save_commit_buffer = 1;
 
@@ -221,6 +222,8 @@ static void prepare_commit_graft(void)
 		return;
 	graft_file = get_graft_file();
 	read_graft_file(graft_file);
+	/* make sure shallows are read */
+	is_repository_shallow();
 	commit_graft_prepared = 1;
 }
 
@@ -234,6 +237,37 @@ static struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 	return commit_graft[pos];
 }
 
+int write_shallow_commits(int fd, int use_pack_protocol)
+{
+	int i, count = 0;
+	for (i = 0; i < commit_graft_nr; i++)
+		if (commit_graft[i]->nr_parent < 0) {
+			const char *hex =
+				sha1_to_hex(commit_graft[i]->sha1);
+			count++;
+			if (use_pack_protocol)
+				packet_write(fd, "shallow %s", hex);
+			else {
+				write(fd, hex,  40);
+				write(fd, "\n", 1);
+			}
+		}
+	return count;
+}
+
+int unregister_shallow(const unsigned char *sha1)
+{
+	int pos = commit_graft_pos(sha1);
+	if (pos < 0)
+		return -1;
+	if (pos + 1 < commit_graft_nr)
+		memcpy(commit_graft + pos, commit_graft + pos + 1,
+				sizeof(struct commit_graft *)
+				* (commit_graft_nr - pos - 1));
+	commit_graft_nr--;
+	return 0;
+}
+
 int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 {
 	char *tail = buffer;
diff --git a/commit.h b/commit.h
index 10eea9f26f..936f8fce30 100644
--- a/commit.h
+++ b/commit.h
@@ -97,7 +97,7 @@ void sort_in_topological_order_fn(struct commit_list ** list, int lifo,
 
 struct commit_graft {
 	unsigned char sha1[20];
-	int nr_parent;
+	int nr_parent; /* < 0 if shallow commit */
 	unsigned char parent[FLEX_ARRAY][20]; /* more */
 };
 
@@ -107,5 +107,12 @@ int read_graft_file(const char *graft_file);
 
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2, int cleanup);
 
+extern int register_shallow(const unsigned char *sha1);
+extern int unregister_shallow(const unsigned char *sha1);
+extern int write_shallow_commits(int fd, int use_pack_protocol);
+extern int is_repository_shallow();
+extern struct commit_list *get_shallow_commits(struct object_array *heads,
+		int depth, int shallow_flag, int not_shallow_flag);
+
 int in_merge_bases(struct commit *rev1, struct commit *rev2);
 #endif /* COMMIT_H */
diff --git a/fetch-pack.c b/fetch-pack.c
index 92322cf4da..c527bf9e96 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -10,8 +10,9 @@ static int keep_pack;
 static int quiet;
 static int verbose;
 static int fetch_all;
+static int depth;
 static const char fetch_pack_usage[] =
-"git-fetch-pack [--all] [-q] [-v] [-k] [--thin] [--exec=upload-pack] [host:]directory <refs>...";
+"git-fetch-pack [--all] [-q] [-v] [-k] [--thin] [--exec=upload-pack] [--depth=<n>] [host:]directory <refs>...";
 static const char *exec = "git-upload-pack";
 
 #define COMPLETE	(1U << 0)
@@ -179,10 +180,41 @@ static int find_common(int fd[2], unsigned char *result_sha1,
 			packet_write(fd[1], "want %s\n", sha1_to_hex(remote));
 		fetching++;
 	}
+	if (is_repository_shallow())
+		write_shallow_commits(fd[1], 1);
+	if (depth > 0)
+		packet_write(fd[1], "deepen %d", depth);
 	packet_flush(fd[1]);
 	if (!fetching)
 		return 1;
 
+	if (depth > 0) {
+		char line[1024];
+		unsigned char sha1[20];
+		int len;
+
+		while ((len = packet_read_line(fd[0], line, sizeof(line)))) {
+			if (!strncmp("shallow ", line, 8)) {
+				if (get_sha1_hex(line + 8, sha1))
+					die("invalid shallow line: %s", line);
+				register_shallow(sha1);
+				continue;
+			}
+			if (!strncmp("unshallow ", line, 10)) {
+				if (get_sha1_hex(line + 10, sha1))
+					die("invalid unshallow line: %s", line);
+				if (!lookup_object(sha1))
+					die("object not found: %s", line);
+				/* make sure that it is parsed as shallow */
+				parse_object(sha1);
+				if (unregister_shallow(sha1))
+					die("no shallow found: %s", line);
+				continue;
+			}
+			die("expected shallow/unshallow, got %s", line);
+		}
+	}
+
 	flushes = 0;
 	retval = -1;
 	while ((sha1 = get_rev())) {
@@ -309,7 +341,8 @@ static void filter_refs(struct ref **refs, int nr_match, char **match)
 		if (!memcmp(ref->name, "refs/", 5) &&
 		    check_ref_format(ref->name + 5))
 			; /* trash */
-		else if (fetch_all) {
+		else if (fetch_all &&
+			 (!depth || strncmp(ref->name, "refs/tags/", 10) )) {
 			*newtail = ref;
 			ref->next = NULL;
 			newtail = &ref->next;
@@ -368,9 +401,11 @@ static int everything_local(struct ref **refs, int nr_match, char **match)
 		}
 	}
 
-	for_each_ref(mark_complete, NULL);
-	if (cutoff)
-		mark_recent_complete_commits(cutoff);
+	if (!depth) {
+		for_each_ref(mark_complete, NULL);
+		if (cutoff)
+			mark_recent_complete_commits(cutoff);
+	}
 
 	/*
 	 * Mark all complete remote refs as common refs.
@@ -522,6 +557,8 @@ static int fetch_pack(int fd[2], int nr_match, char **match)
 	int status;
 
 	get_remote_heads(fd[0], &ref, 0, NULL, 0);
+	if (is_repository_shallow() && !server_supports("shallow"))
+		die("Server does not support shallow clients");
 	if (server_supports("multi_ack")) {
 		if (verbose)
 			fprintf(stderr, "Server supports multi_ack\n");
@@ -594,6 +631,8 @@ int main(int argc, char **argv)
 	char *dest = NULL, **heads;
 	int fd[2];
 	pid_t pid;
+	struct stat st;
+	struct lock_file lock;
 
 	setup_git_directory();
 
@@ -627,6 +666,12 @@ int main(int argc, char **argv)
 				verbose = 1;
 				continue;
 			}
+			if (!strncmp("--depth=", arg, 8)) {
+				depth = strtol(arg + 8, NULL, 0);
+				if (stat(git_path("shallow"), &st))
+					st.st_mtime = 0;
+				continue;
+			}
 			usage(fetch_pack_usage);
 		}
 		dest = arg;
@@ -659,5 +704,34 @@ int main(int argc, char **argv)
 			}
 	}
 
+	if (!ret && depth > 0) {
+		struct cache_time mtime;
+		char *shallow = git_path("shallow");
+		int fd;
+
+		mtime.sec = st.st_mtime;
+#ifdef USE_NSEC
+		mtime.usec = st.st_mtim.usec;
+#endif
+		if (stat(shallow, &st)) {
+			if (mtime.sec)
+				die("shallow file was removed during fetch");
+		} else if (st.st_mtime != mtime.sec
+#ifdef USE_NSEC
+				|| st.st_mtim.usec != mtime.usec
+#endif
+			  )
+			die("shallow file was changed during fetch");
+
+		fd = hold_lock_file_for_update(&lock, shallow, 1);
+		if (!write_shallow_commits(fd, 0)) {
+			unlink(shallow);
+			rollback_lock_file(&lock);
+		} else {
+			close(fd);
+			commit_lock_file(&lock);
+		}
+	}
+
 	return !!ret;
 }
diff --git a/git-clone.sh b/git-clone.sh
index 490f3e48db..f37eb9d105 100755
--- a/git-clone.sh
+++ b/git-clone.sh
@@ -14,7 +14,7 @@ die() {
 }
 
 usage() {
-	die "Usage: $0 [--template=<template_directory>] [--reference <reference-repo>] [--bare] [-l [-s]] [-q] [-u <upload-pack>] [--origin <name>] [-n] <repo> [<dir>]"
+	die "Usage: $0 [--template=<template_directory>] [--reference <reference-repo>] [--bare] [-l [-s]] [-q] [-u <upload-pack>] [--origin <name>] [--depth <n>] [-n] <repo> [<dir>]"
 }
 
 get_repo_base() {
@@ -120,6 +120,7 @@ reference=
 origin=
 origin_override=
 use_separate_remote=t
+depth=
 while
 	case "$#,$1" in
 	0,*) break ;;
@@ -163,6 +164,10 @@ while
 	*,-u|*,--upload-pack)
 		shift
 		upload_pack="--exec=$1" ;;
+	1,--depth) usage;;
+	*,--depth)
+		shift
+		depth="--depth=$1";;
 	*,-*) usage ;;
 	*) break ;;
 	esac
@@ -267,6 +272,10 @@ yes,yes)
 *)
 	case "$repo" in
 	rsync://*)
+		case "$depth" in
+		"") ;;
+		*) die "shallow over rsync not supported" ;;
+		esac
 		rsync $quiet -av --ignore-existing  \
 			--exclude info "$repo/objects/" "$GIT_DIR/objects/" ||
 		exit
@@ -295,6 +304,10 @@ yes,yes)
 		git-ls-remote "$repo" >"$GIT_DIR/CLONE_HEAD" || exit 1
 		;;
 	https://*|http://*|ftp://*)
+		case "$depth" in
+		"") ;;
+		*) die "shallow over http or ftp not supported" ;;
+		esac
 		if test -z "@@NO_CURL@@"
 		then
 			clone_dumb_http "$repo" "$D"
@@ -304,8 +317,8 @@ yes,yes)
 		;;
 	*)
 		case "$upload_pack" in
-		'') git-fetch-pack --all -k $quiet "$repo" ;;
-		*) git-fetch-pack --all -k $quiet "$upload_pack" "$repo" ;;
+		'') git-fetch-pack --all -k $quiet $depth "$repo" ;;
+		*) git-fetch-pack --all -k $quiet "$upload_pack" $depth "$repo" ;;
 		esac >"$GIT_DIR/CLONE_HEAD" ||
 			die "fetch-pack from '$repo' failed."
 		;;
diff --git a/git-fetch.sh b/git-fetch.sh
index 7fb47f69fb..8bd11f8b60 100755
--- a/git-fetch.sh
+++ b/git-fetch.sh
@@ -28,6 +28,7 @@ update_head_ok=
 exec=
 upload_pack=
 keep=
+shallow_depth=
 while case "$#" in 0) break ;; esac
 do
 	case "$1" in
@@ -60,6 +61,13 @@ do
 	-k|--k|--ke|--kee|--keep)
 		keep='-k -k'
 		;;
+	--depth=*)
+		shallow_depth="--depth=`expr "z$1" : 'z-[^=]*=\(.*\)'`"
+		;;
+	--depth)
+		shift
+		shallow_depth="--depth=$1"
+		;;
 	-*)
 		usage
 		;;
@@ -300,6 +308,8 @@ fetch_main () {
       # There are transports that can fetch only one head at a time...
       case "$remote" in
       http://* | https://* | ftp://*)
+	  test -n "$shallow_depth" &&
+		die "shallow clone with http not supported"
 	  proto=`expr "$remote" : '\([^:]*\):'`
 	  if [ -n "$GIT_SSL_NO_VERIFY" ]; then
 	      curl_extra_args="-k"
@@ -326,6 +336,8 @@ fetch_main () {
 	  git-http-fetch -v -a "$head" "$remote/" || exit
 	  ;;
       rsync://*)
+	  test -n "$shallow_depth" &&
+		die "shallow clone with rsync not supported"
 	  TMP_HEAD="$GIT_DIR/TMP_HEAD"
 	  rsync -L -q "$remote/$remote_name" "$TMP_HEAD" || exit 1
 	  head=$(git-rev-parse --verify TMP_HEAD)
@@ -373,7 +385,7 @@ fetch_main () {
       pack_lockfile=
       IFS=" 	$LF"
       (
-	  git-fetch-pack --thin $exec $keep "$remote" $rref || echo failed "$remote"
+	  git-fetch-pack --thin $exec $keep $shallow_depth "$remote" $rref || echo failed "$remote"
       ) |
       while read sha1 remote_name
       do
@@ -446,6 +458,8 @@ case "$no_tags$tags" in
 	case "$taglist" in
 	'') ;;
 	?*)
+		# do not deepen a shallow tree when following tags
+		shallow_depth=
 		fetch_main "$taglist" || exit ;;
 	esac
 esac
diff --git a/shallow.c b/shallow.c
new file mode 100644
index 0000000000..3d53d17423
--- /dev/null
+++ b/shallow.c
@@ -0,0 +1,104 @@
+#include "cache.h"
+#include "commit.h"
+#include "tag.h"
+
+static int is_shallow = -1;
+
+int register_shallow(const unsigned char *sha1)
+{
+	struct commit_graft *graft =
+		xmalloc(sizeof(struct commit_graft));
+	struct commit *commit = lookup_commit(sha1);
+
+	hashcpy(graft->sha1, sha1);
+	graft->nr_parent = -1;
+	if (commit && commit->object.parsed)
+		commit->parents = NULL;
+	return register_commit_graft(graft, 0);
+}
+
+int is_repository_shallow()
+{
+	FILE *fp;
+	char buf[1024];
+
+	if (is_shallow >= 0)
+		return is_shallow;
+
+	fp = fopen(git_path("shallow"), "r");
+	if (!fp) {
+		is_shallow = 0;
+		return is_shallow;
+	}
+	is_shallow = 1;
+
+	while (fgets(buf, sizeof(buf), fp)) {
+		unsigned char sha1[20];
+		if (get_sha1_hex(buf, sha1))
+			die("bad shallow line: %s", buf);
+		register_shallow(sha1);
+	}
+	fclose(fp);
+	return is_shallow;
+}
+
+struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
+		int shallow_flag, int not_shallow_flag)
+{
+	int i = 0, cur_depth = 0;
+	struct commit_list *result = NULL;
+	struct object_array stack = {0, 0, NULL};
+	struct commit *commit = NULL;
+
+	while (commit || i < heads->nr || stack.nr) {
+		struct commit_list *p;
+		if (!commit) {
+			if (i < heads->nr) {
+				commit = (struct commit *)
+					deref_tag(heads->objects[i++].item, NULL, 0);
+				if (commit->object.type != OBJ_COMMIT) {
+					commit = NULL;
+					continue;
+				}
+				if (!commit->util)
+					commit->util = xmalloc(sizeof(int));
+				*(int *)commit->util = 0;
+				cur_depth = 0;
+			} else {
+				commit = (struct commit *)
+					stack.objects[--stack.nr].item;
+				cur_depth = *(int *)commit->util;
+			}
+		}
+		parse_commit(commit);
+		commit->object.flags |= not_shallow_flag;
+		cur_depth++;
+		for (p = commit->parents, commit = NULL; p; p = p->next) {
+			if (!p->item->util) {
+				int *pointer = xmalloc(sizeof(int));
+				p->item->util = pointer;
+				*pointer =  cur_depth;
+			} else {
+				int *pointer = p->item->util;
+				if (cur_depth >= *pointer)
+					continue;
+				*pointer = cur_depth;
+			}
+			if (cur_depth < depth) {
+				if (p->next)
+					add_object_array(&p->item->object,
+							NULL, &stack);
+				else {
+					commit = p->item;
+					cur_depth = *(int *)commit->util;
+				}
+			} else {
+				commit_list_insert(p->item, &result);
+				p->item->object.flags |= shallow_flag;
+			}
+		}
+	}
+
+	return result;
+}
+
diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index f7625a6f46..77c3c575d8 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -128,4 +128,54 @@ pull_to_client 2nd "B" $((64*3))
 
 pull_to_client 3rd "A" $((1*3)) # old fails
 
+test_expect_success "clone shallow" "git-clone --depth 2 . shallow"
+
+(cd shallow; git-count-objects -v) > count.shallow
+
+test_expect_success "clone shallow object count" \
+	"test \"in-pack: 18\" = \"$(grep in-pack count.shallow)\""
+
+count_output () {
+	sed -e '/^in-pack:/d' -e '/^packs:/d' -e '/: 0$/d' "$1"
+}
+
+test_expect_success "clone shallow object count (part 2)" '
+	test -z "$(count_output count.shallow)"
+'
+
+test_expect_success "fsck in shallow repo" \
+	"(cd shallow; git-fsck-objects --full)"
+
+#test_done; exit
+
+add B66 $B65
+add B67 $B66
+
+test_expect_success "pull in shallow repo" \
+	"(cd shallow; git pull .. B)"
+
+(cd shallow; git-count-objects -v) > count.shallow
+test_expect_success "clone shallow object count" \
+	"test \"count: 6\" = \"$(grep count count.shallow)\""
+
+add B68 $B67
+add B69 $B68
+
+test_expect_success "deepening pull in shallow repo" \
+	"(cd shallow; git pull --depth 4 .. B)"
+
+(cd shallow; git-count-objects -v) > count.shallow
+test_expect_success "clone shallow object count" \
+	"test \"count: 12\" = \"$(grep count count.shallow)\""
+
+test_expect_success "deepening fetch in shallow repo" \
+	"(cd shallow; git fetch --depth 4 .. A:A)"
+
+(cd shallow; git-count-objects -v) > count.shallow
+test_expect_success "clone shallow object count" \
+	"test \"count: 18\" = \"$(grep count count.shallow)\""
+
+test_expect_failure "pull in shallow repo with missing merge base" \
+	"(cd shallow; git pull --depth 4 .. A)"
+
 test_done
diff --git a/upload-pack.c b/upload-pack.c
index 32b06b2e66..c568ef066c 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -6,6 +6,9 @@
 #include "object.h"
 #include "commit.h"
 #include "exec_cmd.h"
+#include "diff.h"
+#include "revision.h"
+#include "list-objects.h"
 
 static const char upload_pack_usage[] = "git-upload-pack [--strict] [--timeout=nn] <dir>";
 
@@ -16,6 +19,10 @@ static const char upload_pack_usage[] = "git-upload-pack [--strict] [--timeout=n
 #define COMMON_KNOWN	(1u << 14)
 #define REACHABLE	(1u << 15)
 
+#define SHALLOW		(1u << 16)
+#define NOT_SHALLOW	(1u << 17)
+#define CLIENT_SHALLOW	(1u << 18)
+
 static unsigned long oldest_have;
 
 static int multi_ack, nr_our_refs;
@@ -54,6 +61,40 @@ static ssize_t send_client_data(int fd, const char *data, ssize_t sz)
 	return safe_write(fd, data, sz);
 }
 
+FILE *pack_pipe = NULL;
+static void show_commit(struct commit *commit)
+{
+	if (commit->object.flags & BOUNDARY)
+		fputc('-', pack_pipe);
+	if (fputs(sha1_to_hex(commit->object.sha1), pack_pipe) < 0)
+		die("broken output pipe");
+	fputc('\n', pack_pipe);
+	fflush(pack_pipe);
+	free(commit->buffer);
+	commit->buffer = NULL;
+}
+
+static void show_object(struct object_array_entry *p)
+{
+	/* An object with name "foo\n0000000..." can be used to
+	 * confuse downstream git-pack-objects very badly.
+	 */
+	const char *ep = strchr(p->name, '\n');
+	if (ep) {
+		fprintf(pack_pipe, "%s %.*s\n", sha1_to_hex(p->item->sha1),
+		       (int) (ep - p->name),
+		       p->name);
+	}
+	else
+		fprintf(pack_pipe, "%s %s\n",
+				sha1_to_hex(p->item->sha1), p->name);
+}
+
+static void show_edge(struct commit *commit)
+{
+	fprintf(pack_pipe, "-%s\n", sha1_to_hex(commit->object.sha1));
+}
+
 static void create_pack_file(void)
 {
 	/* Pipes between rev-list to pack-objects, pack-objects to us
@@ -75,48 +116,40 @@ static void create_pack_file(void)
 
 	if (!pid_rev_list) {
 		int i;
-		int args;
-		const char **argv;
-		const char **p;
-		char *buf;
+		struct rev_info revs;
 
-		if (create_full_pack) {
-			args = 10;
-			use_thin_pack = 0; /* no point doing it */
-		}
-		else
-			args = have_obj.nr + want_obj.nr + 5;
-		p = xmalloc(args * sizeof(char *));
-		argv = (const char **) p;
-		buf = xmalloc(args * 45);
+		pack_pipe = fdopen(lp_pipe[1], "w");
 
-		dup2(lp_pipe[1], 1);
-		close(0);
-		close(lp_pipe[0]);
-		close(lp_pipe[1]);
-		*p++ = "rev-list";
-		*p++ = use_thin_pack ? "--objects-edge" : "--objects";
 		if (create_full_pack)
-			*p++ = "--all";
-		else {
+			use_thin_pack = 0; /* no point doing it */
+		init_revisions(&revs, NULL);
+		revs.tag_objects = 1;
+		revs.tree_objects = 1;
+		revs.blob_objects = 1;
+		if (use_thin_pack)
+			revs.edge_hint = 1;
+
+		if (create_full_pack) {
+			const char *args[] = {"rev-list", "--all", NULL};
+			setup_revisions(2, args, &revs, NULL);
+		} else {
 			for (i = 0; i < want_obj.nr; i++) {
 				struct object *o = want_obj.objects[i].item;
-				*p++ = buf;
-				memcpy(buf, sha1_to_hex(o->sha1), 41);
-				buf += 41;
+				/* why??? */
+				o->flags &= ~UNINTERESTING;
+				add_pending_object(&revs, o, NULL);
 			}
-		}
-		if (!create_full_pack)
 			for (i = 0; i < have_obj.nr; i++) {
 				struct object *o = have_obj.objects[i].item;
-				*p++ = buf;
-				*buf++ = '^';
-				memcpy(buf, sha1_to_hex(o->sha1), 41);
-				buf += 41;
+				o->flags |= UNINTERESTING;
+				add_pending_object(&revs, o, NULL);
 			}
-		*p++ = NULL;
-		execv_git_cmd(argv);
-		die("git-upload-pack: unable to exec git-rev-list");
+			setup_revisions(0, NULL, &revs, NULL);
+		}
+		prepare_revision_walk(&revs);
+		mark_edges_uninteresting(revs.commits, &revs, show_edge);
+		traverse_commit_list(&revs, show_commit, show_object);
+		exit(0);
 	}
 
 	if (pipe(pu_pipe) < 0)
@@ -456,8 +489,9 @@ static int get_common_commits(void)
 
 static void receive_needs(void)
 {
+	struct object_array shallows = {0, 0, NULL};
 	static char line[1000];
-	int len;
+	int len, depth = 0;
 
 	for (;;) {
 		struct object *o;
@@ -465,8 +499,29 @@ static void receive_needs(void)
 		len = packet_read_line(0, line, sizeof(line));
 		reset_timeout();
 		if (!len)
-			return;
+			break;
 
+		if (!strncmp("shallow ", line, 8)) {
+			unsigned char sha1[20];
+			struct object *object;
+			use_thin_pack = 0;
+			if (get_sha1(line + 8, sha1))
+				die("invalid shallow line: %s", line);
+			object = parse_object(sha1);
+			if (!object)
+				die("did not find object for %s", line);
+			object->flags |= CLIENT_SHALLOW;
+			add_object_array(object, NULL, &shallows);
+			continue;
+		}
+		if (!strncmp("deepen ", line, 7)) {
+			char *end;
+			use_thin_pack = 0;
+			depth = strtol(line + 7, &end, 0);
+			if (end == line + 7 || depth <= 0)
+				die("Invalid deepen: %s", line);
+			continue;
+		}
 		if (strncmp("want ", line, 5) ||
 		    get_sha1_hex(line+5, sha1_buf))
 			die("git-upload-pack: protocol error, "
@@ -498,11 +553,58 @@ static void receive_needs(void)
 			add_object_array(o, NULL, &want_obj);
 		}
 	}
+	if (depth == 0 && shallows.nr == 0)
+		return;
+	if (depth > 0) {
+		struct commit_list *result, *backup;
+		int i;
+		backup = result = get_shallow_commits(&want_obj, depth,
+			SHALLOW, NOT_SHALLOW);
+		while (result) {
+			struct object *object = &result->item->object;
+			if (!(object->flags & (CLIENT_SHALLOW|NOT_SHALLOW))) {
+				packet_write(1, "shallow %s",
+						sha1_to_hex(object->sha1));
+				register_shallow(object->sha1);
+			}
+			result = result->next;
+		}
+		free_commit_list(backup);
+		for (i = 0; i < shallows.nr; i++) {
+			struct object *object = shallows.objects[i].item;
+			if (object->flags & NOT_SHALLOW) {
+				struct commit_list *parents;
+				packet_write(1, "unshallow %s",
+					sha1_to_hex(object->sha1));
+				object->flags &= ~CLIENT_SHALLOW;
+				/* make sure the real parents are parsed */
+				unregister_shallow(object->sha1);
+				object->parsed = 0;
+				parse_commit((struct commit *)object);
+				parents = ((struct commit *)object)->parents;
+				while (parents) {
+					add_object_array(&parents->item->object,
+							NULL, &want_obj);
+					parents = parents->next;
+				}
+			}
+			/* make sure commit traversal conforms to client */
+			register_shallow(object->sha1);
+		}
+		packet_flush(1);
+	} else
+		if (shallows.nr > 0) {
+			int i;
+			for (i = 0; i < shallows.nr; i++)
+				register_shallow(shallows.objects[i].item->sha1);
+		}
+	free(shallows.objects);
 }
 
 static int send_ref(const char *refname, const unsigned char *sha1, int flag, void *cb_data)
 {
-	static const char *capabilities = "multi_ack thin-pack side-band side-band-64k ofs-delta";
+	static const char *capabilities = "multi_ack thin-pack side-band"
+		" side-band-64k ofs-delta shallow";
 	struct object *o = parse_object(sha1);
 
 	if (!o)