upload-pack: support define shallow boundary by excluding revisions

This should allow the user to say "create a shallow clone of this branch
after version <some-tag>".

Short refs are accepted and expanded at the server side with expand_ref()
because we cannot expand (unknown) refs from the client side.

Like deepen-since, deepen-not cannot be used with deepen. But deepen-not
can be mixed with deepen-since. The result is exactly how you do the
command "git rev-list --since=... --not ref".

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/technical/pack-protocol.txt

@@ -220,7 +220,8 @@ out of what the server said it could do with the first 'want' line.
   shallow-line      =  PKT-LINE("shallow" SP obj-id)
 
   depth-request     =  PKT-LINE("deepen" SP depth) /
-		       PKT-LINE("deepen-since" SP timestamp)
+		       PKT-LINE("deepen-since" SP timestamp) /
+		       PKT-LINE("deepen-not" SP ref)
 
   first-want        =  PKT-LINE("want" SP obj-id SP capability-list)
   additional-want   =  PKT-LINE("want" SP obj-id)

Documentation/technical/protocol-capabilities.txt

@@ -188,6 +188,15 @@ specific time, instead of depth. Internally it's equivalent of doing
 "rev-list --max-age=<timestamp>" on the server side. "deepen-since"
 cannot be used with "deepen".
 
+deepen-not
+----------
+
+This capability adds "deepen-not" command to fetch-pack/upload-pack
+protocol so the client can request shallow clones that are cut at a
+specific revision, instead of depth. Internally it's equivalent of
+doing "rev-list --not <rev>" on the server side. "deepen-not"
+cannot be used with "deepen", but can be used with "deepen-since".
+
 no-progress
 -----------
 

upload-pack.c

@@ -645,6 +645,7 @@ static void deepen_by_rev_list(int ac, const char **av,
 static void receive_needs(void)
 {
 	struct object_array shallows = OBJECT_ARRAY_INIT;
+	struct string_list deepen_not = STRING_LIST_INIT_DUP;
 	int depth = 0;
 	int has_non_tip = 0;
 	unsigned long deepen_since = 0;
@@ -695,6 +696,16 @@ static void receive_needs(void)
 			deepen_rev_list = 1;
 			continue;
 		}
+		if (skip_prefix(line, "deepen-not ", &arg)) {
+			char *ref = NULL;
+			unsigned char sha1[20];
+			if (expand_ref(arg, strlen(arg), sha1, &ref) != 1)
+				die("git upload-pack: ambiguous deepen-not: %s", line);
+			string_list_append(&deepen_not, ref);
+			free(ref);
+			deepen_rev_list = 1;
+			continue;
+		}
 		if (!skip_prefix(line, "want ", &arg) ||
 		    get_sha1_hex(arg, sha1_buf))
 			die("git upload-pack: protocol error, "
@@ -749,7 +760,7 @@ static void receive_needs(void)
 	if (depth == 0 && !deepen_rev_list && shallows.nr == 0)
 		return;
 	if (depth > 0 && deepen_rev_list)
-		die("git upload-pack: deepen and deepen-since cannot be used together");
+		die("git upload-pack: deepen and deepen-since (or deepen-not) cannot be used together");
 	if (depth > 0)
 		deepen(depth, &shallows);
 	else if (deepen_rev_list) {
@@ -759,6 +770,14 @@ static void receive_needs(void)
 		argv_array_push(&av, "rev-list");
 		if (deepen_since)
 			argv_array_pushf(&av, "--max-age=%lu", deepen_since);
+		if (deepen_not.nr) {
+			argv_array_push(&av, "--not");
+			for (i = 0; i < deepen_not.nr; i++) {
+				struct string_list_item *s = deepen_not.items + i;
+				argv_array_push(&av, s->string);
+			}
+			argv_array_push(&av, "--not");
+		}
 		for (i = 0; i < want_obj.nr; i++) {
 			struct object *o = want_obj.objects[i].item;
 			argv_array_push(&av, oid_to_hex(&o->oid));
@@ -814,7 +833,7 @@ static int send_ref(const char *refname, const struct object_id *oid,
 		    int flag, void *cb_data)
 {
 	static const char *capabilities = "multi_ack thin-pack side-band"
-		" side-band-64k ofs-delta shallow deepen-since no-progress"
+		" side-band-64k ofs-delta shallow deepen-since deepen-not no-progress"
 		" include-tag multi_ack_detailed";
 	const char *refname_nons = strip_namespace(refname);
 	struct object_id peeled;