Add the 'shallow' feature to the protocol version 2 command 'fetch'
which indicates that the server supports shallow clients and deepen
requets.

Signed-off-by: Brandon Williams <bmw...@google.com>
---
 Documentation/technical/protocol-v2.txt |  67 +++++++++++++++-
 serve.c                                 |   2 +-
 t/t5701-git-serve.sh                    |   2 +-
 upload-pack.c                           | 138 +++++++++++++++++++++++---------
 upload-pack.h                           |   3 +
 5 files changed, 173 insertions(+), 39 deletions(-)

diff --git a/Documentation/technical/protocol-v2.txt 
b/Documentation/technical/protocol-v2.txt
index 4d5096dae..fedeb6b77 100644
--- a/Documentation/technical/protocol-v2.txt
+++ b/Documentation/technical/protocol-v2.txt
@@ -201,12 +201,42 @@ packet-lines:
        to its base by position in pack rather than by an oid.  That is,
        they can read OBJ_OFS_DELTA (ake type 6) in a packfile.
 
+    shallow <oid>
+       A client must notify the server of all objects for which it only
+       has shallow copies of (meaning that it doesn't have the parents
+       of a commit) by supplying a 'shallow <oid>' line for each such
+       object so that the serve is aware of the limitations of the
+       client's history.
+
+    deepen <depth>
+       Request that the fetch/clone should be shallow having a commit depth of
+       <depth> relative to the remote side.
+
+    deepen-relative
+       Requests that the semantics of the "deepen" command be changed
+       to indicate that the depth requested is relative to the clients
+       current shallow boundary, instead of relative to the remote
+       refs.
+
+    deepen-since <timestamp>
+       Requests that the shallow clone/fetch should be cut at a
+       specific time, instead of depth.  Internally it's equivalent of
+       doing "rev-list --max-age=<timestamp>". Cannot be used with
+       "deepen".
+
+    deepen-not <rev>
+       Requests that the shallow clone/fetch should be cut at a
+       specific revision specified by '<rev>', instead of a depth.
+       Internally it's equivalent of doing "rev-list --not <rev>".
+       Cannot be used with "deepen", but can be used with
+       "deepen-since".
+
 The response of `fetch` is broken into a number of sections separated by
 delimiter packets (0001), with each section beginning with its section
 header.
 
     output = *section
-    section = (acknowledgments | packfile)
+    section = (acknowledgments | shallow-info | packfile)
              (flush-pkt | delim-pkt)
 
     acknowledgments = PKT-LINE("acknowledgments" LF)
@@ -215,6 +245,11 @@ header.
     nak = PKT-LINE("NAK" LF)
     ack = PKT-LINE("ACK" SP obj-id LF)
 
+    shallow-info = PKT-LINE("shallow-info" LF)
+                  *PKT-LINE((shallow | unshallow) LF)
+    shallow = "shallow" SP obj-id
+    unshallow = "unshallow" SP obj-id
+
     packfile = PKT-LINE("packfile" LF)
               [PACKFILE]
 
@@ -247,6 +282,36 @@ header.
          determined the objects it plans to send to the client and no
          further negotiation is needed.
 
+----
+    shallow-info section
+       If the client has requested a shallow fetch/clone, a shallow
+       client requests a fetch or the server is shallow then the
+       server's response may include a shallow-info section.  The
+       shallow-info section will be include if (due to one of the above
+       conditions) the server needs to inform the client of any shallow
+       boundaries or adjustments to the clients already existing
+       shallow boundaries.
+
+       * Always begins with the section header "shallow-info"
+
+       * If a positive depth is requested, the server will compute the
+         set of commits which are no deeper than the desired depth.
+
+       * The server sends a "shallow obj-id" line for each commit whose
+         parents will not be sent in the following packfile.
+
+       * The server sends an "unshallow obj-id" line for each commit
+         which the client has indicated is shallow, but is no longer
+         shallow as a result of the fetch (due to its parents being
+         sent in the following packfile).
+
+       * The server MUST NOT send any "unshallow" lines for anything
+         which the client has not indicated was shallow as a part of
+         its request.
+
+       * This section is only included if a packfile section is also
+         included in the response.
+
 ----
     packfile section
        * Always begins with the section header "packfile"
diff --git a/serve.c b/serve.c
index 05cc434cf..c3e58c1e7 100644
--- a/serve.c
+++ b/serve.c
@@ -53,7 +53,7 @@ struct protocol_capability {
 static struct protocol_capability capabilities[] = {
        { "agent", agent_advertise, NULL },
        { "ls-refs", always_advertise, ls_refs },
-       { "fetch", always_advertise, upload_pack_v2 },
+       { "fetch", upload_pack_advertise, upload_pack_v2 },
 };
 
 static void advertise_capabilities(void)
diff --git a/t/t5701-git-serve.sh b/t/t5701-git-serve.sh
index 202cb782d..491adc693 100755
--- a/t/t5701-git-serve.sh
+++ b/t/t5701-git-serve.sh
@@ -9,7 +9,7 @@ test_expect_success 'test capability advertisement' '
        version 2
        agent=git/$(git version | cut -d" " -f3)
        ls-refs
-       fetch
+       fetch=shallow
        0000
        EOF
 
diff --git a/upload-pack.c b/upload-pack.c
index c6518a24d..a7e4f9e9c 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -710,7 +710,6 @@ static void deepen(int depth, int deepen_relative,
        }
 
        send_unshallow(shallows);
-       packet_flush(1);
 }
 
 static void deepen_by_rev_list(int ac, const char **av,
@@ -722,7 +721,52 @@ static void deepen_by_rev_list(int ac, const char **av,
        send_shallow(result);
        free_commit_list(result);
        send_unshallow(shallows);
-       packet_flush(1);
+}
+
+static int send_shallow_list(int depth, int deepen_rev_list,
+                            timestamp_t deepen_since,
+                            struct string_list *deepen_not,
+                            struct object_array *shallows)
+{
+       int ret = 0;
+
+       if (depth > 0 && deepen_rev_list)
+               die("git upload-pack: deepen and deepen-since (or deepen-not) 
cannot be used together");
+       if (depth > 0) {
+               deepen(depth, deepen_relative, shallows);
+               ret = 1;
+       } else if (deepen_rev_list) {
+               struct argv_array av = ARGV_ARRAY_INIT;
+               int i;
+
+               argv_array_push(&av, "rev-list");
+               if (deepen_since)
+                       argv_array_pushf(&av, "--max-age=%"PRItime, 
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));
+               }
+               deepen_by_rev_list(av.argc, av.argv, shallows);
+               argv_array_clear(&av);
+               ret = 1;
+       } else {
+               if (shallows->nr > 0) {
+                       int i;
+                       for (i = 0; i < shallows->nr; i++)
+                               
register_shallow(&shallows->objects[i].item->oid);
+               }
+       }
+
+       shallow_nr += shallows->nr;
+       return ret;
 }
 
 static int process_shallow(const char *line, struct object_array *shallows)
@@ -884,40 +928,10 @@ 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 (or deepen-not) 
cannot be used together");
-       if (depth > 0)
-               deepen(depth, deepen_relative, &shallows);
-       else if (deepen_rev_list) {
-               struct argv_array av = ARGV_ARRAY_INIT;
-               int i;
 
-               argv_array_push(&av, "rev-list");
-               if (deepen_since)
-                       argv_array_pushf(&av, "--max-age=%"PRItime, 
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));
-               }
-               deepen_by_rev_list(av.argc, av.argv, &shallows);
-               argv_array_clear(&av);
-       }
-       else
-               if (shallows.nr > 0) {
-                       int i;
-                       for (i = 0; i < shallows.nr; i++)
-                               
register_shallow(&shallows.objects[i].item->oid);
-               }
-
-       shallow_nr += shallows.nr;
+       if (send_shallow_list(depth, deepen_rev_list, deepen_since,
+                             &deepen_not, &shallows))
+               packet_flush(1);
        object_array_clear(&shallows);
 }
 
@@ -1071,6 +1085,13 @@ struct upload_pack_data {
        struct object_array wants;
        struct oid_array haves;
 
+       struct object_array shallows;
+       struct string_list deepen_not;
+       int depth;
+       timestamp_t deepen_since;
+       int deepen_rev_list;
+       int deepen_relative;
+
        unsigned stateless_rpc : 1;
 
        unsigned use_thin_pack : 1;
@@ -1080,12 +1101,14 @@ struct upload_pack_data {
        unsigned done : 1;
 };
 
-#define UPLOAD_PACK_DATA_INIT { OBJECT_ARRAY_INIT, OID_ARRAY_INIT, 0, 0, 0, 0, 
0, 0 }
+#define UPLOAD_PACK_DATA_INIT { OBJECT_ARRAY_INIT, OID_ARRAY_INIT, 
OBJECT_ARRAY_INIT, STRING_LIST_INIT_DUP, 0, 0, 0, 0, 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);
+       object_array_clear(&data->shallows);
+       string_list_clear(&data->deepen_not, 0);
 }
 
 static int parse_want(const char *line)
@@ -1170,6 +1193,22 @@ static void process_args(struct argv_array *args, struct 
upload_pack_data *data)
                        continue;
                }
 
+               /* Shallow related arguments */
+               if (process_shallow(arg, &data->shallows))
+                       continue;
+               if (process_deepen(arg, &data->depth))
+                       continue;
+               if (process_deepen_since(arg, &data->deepen_since,
+                                        &data->deepen_rev_list))
+                       continue;
+               if (process_deepen_not(arg, &data->deepen_not,
+                                      &data->deepen_rev_list))
+                       continue;
+               if (!strcmp(arg, "deepen-relative")) {
+                       data->deepen_relative = 1;
+                       continue;
+               }
+
                /* ignore unknown lines maybe? */
                die("unexpect line: '%s'", arg);
        }
@@ -1284,6 +1323,23 @@ static int process_haves_and_send_acks(struct 
upload_pack_data *data)
        return ret;
 }
 
+static void send_shallow_info(struct upload_pack_data *data)
+{
+       /* No shallow info needs to be sent */
+       if (!data->depth && !data->deepen_rev_list && !data->shallows.nr &&
+           !is_repository_shallow())
+               return;
+
+       packet_write_fmt(1, "shallow-info\n");
+
+       if (!send_shallow_list(data->depth, data->deepen_rev_list,
+                              data->deepen_since, &data->deepen_not,
+                              &data->shallows) && is_repository_shallow())
+               deepen(INFINITE_DEPTH, data->deepen_relative, &data->shallows);
+
+       packet_delim(1);
+}
+
 enum fetch_state {
        FETCH_PROCESS_ARGS = 0,
        FETCH_READ_HAVES,
@@ -1334,6 +1390,8 @@ int upload_pack_v2(struct repository *r, struct 
argv_array *keys,
                                state = FETCH_DONE;
                        break;
                case FETCH_SEND_PACK:
+                       send_shallow_info(&data);
+
                        packet_write_fmt(1, "packfile\n");
                        create_pack_file();
                        state = FETCH_DONE;
@@ -1346,3 +1404,11 @@ int upload_pack_v2(struct repository *r, struct 
argv_array *keys,
        upload_pack_data_clear(&data);
        return 0;
 }
+
+int upload_pack_advertise(struct repository *r,
+                         struct strbuf *value)
+{
+       if (value)
+               strbuf_addstr(value, "shallow");
+       return 1;
+}
diff --git a/upload-pack.h b/upload-pack.h
index 6b7890238..7720f2142 100644
--- a/upload-pack.h
+++ b/upload-pack.h
@@ -14,5 +14,8 @@ struct repository;
 struct argv_array;
 extern int upload_pack_v2(struct repository *r, struct argv_array *keys,
                          struct argv_array *args);
+struct strbuf;
+extern int upload_pack_advertise(struct repository *r,
+                                struct strbuf *value);
 
 #endif /* UPLOAD_PACK_H */
-- 
2.16.0.rc1.238.g530d649a79-goog

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