Subject: [PATCH 19/26] upload-pack: introduce fetch server command

From: Brandon Williams <[email-masked]>
Date: Tue, 2 Jan 2018 16:18:21 -0800

Introduce the 'fetch' server command.

Signed-off-by: Brandon Williams <[email-masked]>
---
 Documentation/technical/protocol-v2.txt |  14 ++
 serve.c                                 |   2 +
 upload-pack.c                           | 290 ++++++++++++++++++++++++++++++++
 upload-pack.h                           |   9 +
 4 files changed, 315 insertions(+)
 create mode 100644 upload-pack.h

diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt
index 5f4d0e719..2a8e2f226 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -115,3 +115,17 @@ The output of ls-refs is as follows:
 
     symref = PKT-LINE("symref" SP symbolic-ref SP resolved-ref LF)
     shallow = PKT-LINE("shallow" SP obj-id LF)
+
+ Fetch
+-------
+
+Fetch will need to be a modified version of the v1 fetch protocol.  Some
+potential areas for improvement are: Ref-in-want, CDN offloading,
+Fetch-options.
+
+Since we'll have an 'ls-ref' service we can eliminate the need of fetch
+to perform a ref-advertisement, instead a client can run the 'ls-refs'
+service first, in order to find out what refs the server has, and then
+request those refs directly using the fetch service.
+
+//TODO Flesh out the design
diff --git a/serve.c b/serve.c
index 88d548410..ca3bb7190 100644
--- a/serve.c
+++ b/serve.c
@@ -6,6 +6,7 @@
 #include "argv-array.h"
 #include "ls-refs.h"
 #include "serve.h"
+#include "upload-pack.h"
 
 static int always_advertise(struct repository *r,
 			    struct strbuf *value)
@@ -46,6 +47,7 @@ static struct protocol_capability capabilities[] = {
 	{ "agent", agent_advertise, NULL },
 	{ "stateless-rpc", always_advertise, NULL },
 	{ "ls-refs", always_advertise, ls_refs },
+	{ "fetch", always_advertise, upload_pack_v2 },
 };
 
 static void advertise_capabilities(void)
diff --git a/upload-pack.c b/upload-pack.c
index 2ca60d27c..c41f6f528 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -20,6 +20,7 @@
 #include "prio-queue.h"
 #include "protocol.h"
 #include "serve.h"
+#include "upload-pack.h"
 
 static const char * const upload_pack_usage[] = {
 	N_("git upload-pack [<options>] <dir>"),
@@ -1040,6 +1041,295 @@ static void upload_pack(void)
 	}
 }
 
+struct upload_pack_data {
+	struct object_array wants;
+	struct oid_array haves;
+
+	unsigned stateless_rpc : 1;
+
+	unsigned use_thin_pack : 1;
+	unsigned use_ofs_delta : 1;
+	unsigned no_progress : 1;
+	unsigned use_include_tag : 1;
+	unsigned done : 1;
+};
+
+#define UPLOAD_PACK_DATA_INIT { OBJECT_ARRAY_INIT, OID_ARRAY_INIT, 0, 0, 0, 0, 0, 0 }
+
+static void upload_pack_data_clear(struct upload_pack_data *data)
+{
+	object_array_clear(&data->wants);
+	oid_array_clear(&data->haves);
+}
+
+static int parse_want(const char *line)
+{
+	const char *arg;
+	if (skip_prefix(line, "want ", &arg)) {
+		struct object_id oid;
+		struct object *o;
+
+		if (get_oid_hex(arg, &oid))
+			die("git upload-pack: protocol error, "
+			    "expected to get oid, not '%s'", line);
+
+		o = parse_object(&oid);
+		if (!o) {
+			packet_write_fmt(1,
+					 "ERR upload-pack: not our ref %s",
+					 oid_to_hex(&oid));
+			die("git upload-pack: not our ref %s",
+			    oid_to_hex(&oid));
+		}
+
+		if (!(o->flags & WANTED)) {
+			o->flags |= WANTED;
+			add_object_array(o, NULL, &want_obj);
+		}
+
+		return 1;
+	}
+
+	return 0;
+}
+
+static int parse_have(const char *line, struct oid_array *haves)
+{
+	const char *arg;
+	if (skip_prefix(line, "have ", &arg)) {
+		struct object_id oid;
+
+		if (get_oid_hex(arg, &oid))
+			die("git upload-pack: expected SHA1 object, got '%s'", arg);
+		oid_array_append(haves, &oid);
+		return 1;
+	}
+
+	return 0;
+}
+
+static void process_args(struct argv_array *args, struct upload_pack_data *data)
+{
+	int i;
+
+	for (i = 0; i < args->argc; i++) {
+		const char *arg = args->argv[i];
+
+		/* process want */
+		if (parse_want(arg))
+			continue;
+		/* process have line */
+		if (parse_have(arg, &data->haves))
+			continue;
+
+		/* process args like thin-pack */
+		if (!strcmp(arg, "thin-pack")) {
+			use_thin_pack = 1;
+			continue;
+		}
+		if (!strcmp(arg, "ofs-delta")) {
+			use_ofs_delta = 1;
+			continue;
+		}
+		if (!strcmp(arg, "no-progress")) {
+			no_progress = 1;
+			continue;
+		}
+		if (!strcmp(arg, "include-tag")) {
+			use_include_tag = 1;
+			continue;
+		}
+		if (!strcmp(arg, "done")) {
+			data->done = 1;
+			continue;
+		}
+
+		/* ignore unknown lines maybe? */
+		die("unexpect line: '%s'", arg);
+	}
+}
+
+static void read_haves(struct upload_pack_data *data)
+{
+	struct packet_reader reader;
+	packet_reader_init(&reader, 0, NULL, 0,
+			   PACKET_READ_CHOMP_NEWLINE);
+
+	while (packet_reader_read(&reader) == PACKET_READ_NORMAL) {
+
+		if (parse_have(reader.line, &data->haves))
+			continue;
+		if (!strcmp(reader.line, "done")) {
+			data->done = 1;
+			continue;
+		}
+	}
+	if (reader.status != PACKET_READ_FLUSH)
+		die("ERROR");
+}
+
+static int process_haves(struct oid_array *haves, struct oid_array *common)
+{
+	int i;
+
+	/* Process haves */
+	for (i = 0; i < haves->nr; i++) {
+		const struct object_id *oid = &haves->oid[i];
+		struct object *o;
+		int we_knew_they_have = 0;
+
+		if (!has_object_file(oid))
+			continue;
+
+		oid_array_append(common, oid);
+
+		o = parse_object(oid);
+		if (!o)
+			die("oops (%s)", oid_to_hex(oid));
+		if (o->type == OBJ_COMMIT) {
+			struct commit_list *parents;
+			struct commit *commit = (struct commit *)o;
+			if (o->flags & THEY_HAVE)
+				we_knew_they_have = 1;
+			else
+				o->flags |= THEY_HAVE;
+			if (!oldest_have || (commit->date < oldest_have))
+				oldest_have = commit->date;
+			for (parents = commit->parents;
+			     parents;
+			     parents = parents->next)
+				parents->item->object.flags |= THEY_HAVE;
+		}
+		if (!we_knew_they_have)
+			add_object_array(o, NULL, &have_obj);
+	}
+
+	return 0;
+}
+
+static int send_acks(struct oid_array *acks, struct strbuf *response)
+{
+	int i;
+	/* Send Acks */
+	if (!acks->nr)
+		packet_buf_write(response, "NAK\n");
+
+	for (i = 0; i < acks->nr; i++) {
+		packet_buf_write(response, "ACK %s common\n",
+				 oid_to_hex(&acks->oid[i]));
+	}
+
+	if (ok_to_give_up()) {
+		/* Send Ready */
+		packet_buf_write(response, "ACK %s ready\n",
+				 oid_to_hex(&acks->oid[i-1]));
+		return 1;
+	}
+
+	return 0;
+}
+
+static int process_haves_and_send_acks(struct upload_pack_data *data)
+{
+	struct oid_array common = OID_ARRAY_INIT;
+	struct strbuf response = STRBUF_INIT;
+	int ret = 0;
+
+	process_haves(&data->haves, &common);
+	if (data->done) {
+		ret = 1;
+	} else if (send_acks(&common, &response)) {
+		packet_buf_delim(&response);
+		ret = 1;
+	} else {
+		/* Add Flush */
+		packet_buf_flush(&response);
+		ret = 0;
+	}
+
+	/* Send response */
+	write_or_die(1, response.buf, response.len);
+	strbuf_release(&response);
+
+	oid_array_clear(&data->haves);
+	oid_array_clear(&common);
+	return ret;
+}
+
+#define FETCH_PROCESS_ARGS 0
+#define FETCH_READ_HAVES 1
+#define FETCH_SEND_ACKS 2
+#define FETCH_SEND_PACK 3
+#define FETCH_DONE 4
+
+int upload_pack_v2(struct repository *r, struct argv_array *keys,
+		   struct argv_array *args)
+{
+	int state = FETCH_PROCESS_ARGS;
+	struct upload_pack_data data = UPLOAD_PACK_DATA_INIT;
+	const char *out;
+	use_sideband = LARGE_PACKET_MAX;
+
+	/* Check if cmd is being run as a stateless-rpc */
+	if (has_capability(keys, "stateless-rpc", &out))
+		if (!strcmp(out, "true"))
+			data.stateless_rpc = 1;
+
+	while (state != FETCH_DONE) {
+		switch (state) {
+		case FETCH_PROCESS_ARGS:
+			process_args(args, &data);
+
+			if (!want_obj.nr) {
+				/*
+				 * Request didn't contain any 'want' lines,
+				 * guess they didn't want anything.
+				 */
+				state = FETCH_DONE;
+			} else if (data.haves.nr) {
+				/*
+				 * Request had 'have' lines, so lets ACK them.
+				 */
+				state = FETCH_SEND_ACKS;
+			} else {
+				/*
+				 * Request had 'want's but no 'have's so we can
+				 * immedietly go to construct and send a pack.
+				 */
+				state = FETCH_SEND_PACK;
+			}
+			break;
+		case FETCH_READ_HAVES:
+			read_haves(&data);
+			state = FETCH_SEND_ACKS;
+			break;
+		case FETCH_SEND_ACKS:
+			if (process_haves_and_send_acks(&data))
+				state = FETCH_SEND_PACK;
+			else if (data.stateless_rpc)
+				/*
+				 * Request was made via stateless-rpc and a
+				 * packfile isn't ready to be created and sent.
+				 */
+				state = FETCH_DONE;
+			else
+				state = FETCH_READ_HAVES;
+			break;
+		case FETCH_SEND_PACK:
+			create_pack_file();
+			state = FETCH_DONE;
+			break;
+		case FETCH_DONE:
+			break;
+		default:
+			BUG("invalid state");
+		}
+	}
+
+	upload_pack_data_clear(&data);
+	return 0;
+}
+
 static int upload_pack_config(const char *var, const char *value, void *unused)
 {
 	if (!strcmp("uploadpack.allowtipsha1inwant", var)) {
diff --git a/upload-pack.h b/upload-pack.h
new file mode 100644
index 000000000..54c429563
--- /dev/null
+++ b/upload-pack.h
@@ -0,0 +1,9 @@
+#ifndef UPLOAD_PACK_H
+#define UPLOAD_PACK_H
+
+struct repository;
+struct argv_array;
+extern int upload_pack_v2(struct repository *r, struct argv_array *keys,
+			  struct argv_array *args);
+
+#endif /* UPLOAD_PACK_H */
-- 
2.15.1.620.gb9897f4670-goog