make the sender advertise shallow commits to the receiver

If either receive-pack or upload-pack is called on a shallow
repository, shallow commits (*) will be sent after the ref
advertisement (but before the packet flush), so that the receiver has
the full "shape" of the sender's commit graph. This will be needed for
the receiver to update its .git/shallow if necessary.

This breaks the protocol for all clients trying to push to a shallow
repo, or fetch from one. Which is basically the same end result as
today's "is_repository_shallow() && die()" in receive-pack and
upload-pack. New clients will be made aware of shallow upstream and
can make use of this information.

The sender must send all shallow commits that are sent in the
following pack. It may send more shallow commits than necessary.

upload-pack for example may choose to advertise no shallow commits if
it knows in advance that the pack it's going to send contains no
shallow commits. But upload-pack is the server, so we choose the
cheaper way, send full .git/shallow and let the client deal with it.

Smart HTTP is not affected by this patch. Shallow support on
smart-http comes later separately.

(*) A shallow commit is a commit that terminates the revision
walker. It is usually put in .git/shallow in order to keep the
revision walker from going out of bound because there is no
guarantee that objects behind this commit is available.

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

diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index b898e97988311fe411c02f9f3fe45608e862a71a..eb8edd1d4da4927f75e4ec0eaed5c8cce9ad0352 100644 (file)
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -161,6 +161,7 @@ MUST peel the ref if it's an annotated tag.
 
 ----
   advertised-refs  =  (no-refs / list-of-refs)
+                     *shallow
                      flush-pkt
 
   no-refs          =  PKT-LINE(zero-id SP "capabilities^{}"
@@ -174,6 +175,8 @@ MUST peel the ref if it's an annotated tag.
   other-tip        =  obj-id SP refname LF
   other-peeled     =  obj-id SP refname "^{}" LF
 
+  shallow          =  PKT-LINE("shallow" SP obj-id)
+
   capability-list  =  capability *(SP capability)
   capability       =  1*(LC_ALPHA / DIGIT / "-" / "_")
   LC_ALPHA         =  %x61-7A

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 67ce1ef105d1494e7905e66750b14676e082e11c..cc8c34f021918996d91806ecc8f36a9584fc3384 100644 (file)
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -178,6 +178,8 @@ static void write_head_info(void)
        if (!sent_capabilities)
                show_ref("capabilities^{}", null_sha1);
 
+       advertise_shallow_grafts(1);
+
        /* EOF */
        packet_flush(1);
 }
@@ -998,7 +1000,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
        if (!enter_repo(dir, 0))
                die("'%s' does not appear to be a git repository", dir);
 
-       if (is_repository_shallow())
+       if (is_repository_shallow() && stateless_rpc)
                die("attempt to push into a shallow repository");
 
        git_config(receive_pack_config, NULL);

diff --git a/commit.h b/commit.h
index bd841f4d0c5e2b7fb8e83d55ba0d0b7e2839bf8a..a8795263b6778584d08e747391aa9f2a316f17cf 100644 (file)
--- a/commit.h
+++ b/commit.h
@@ -205,6 +205,7 @@ extern int write_shallow_commits(struct strbuf *out, int use_pack_protocol);
 extern void setup_alternate_shallow(struct lock_file *shallow_lock,
                                    const char **alternate_shallow_file);
 extern char *setup_temporary_shallow(void);
+extern void advertise_shallow_grafts(int);
 
 int is_descendant_of(struct commit *, struct commit_list *);
 int in_merge_bases(struct commit *, struct commit *);

diff --git a/shallow.c b/shallow.c
index cdf37d694de175adcce10fa2e2a79c6579603b0b..f2c04b28dca0404fe00cdd6f2e2f9424d28aed32 100644 (file)
--- a/shallow.c
+++ b/shallow.c
@@ -220,3 +220,18 @@ void setup_alternate_shallow(struct lock_file *shallow_lock,
                *alternate_shallow_file = "";
        strbuf_release(&sb);
 }
+
+static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
+{
+       int fd = *(int *)cb;
+       if (graft->nr_parent == -1)
+               packet_write(fd, "shallow %s\n", sha1_to_hex(graft->sha1));
+       return 0;
+}
+
+void advertise_shallow_grafts(int fd)
+{
+       if (!is_repository_shallow())
+               return;
+       for_each_commit_graft(advertise_shallow_grafts_cb, &fd);
+}

diff --git a/upload-pack.c b/upload-pack.c
index c989a737f975b3aef41ffb9f6ec669ce3b2f2c2b..38b2a2911044646b6673344d77a56062b6170023 100644 (file)
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -758,6 +758,7 @@ static void upload_pack(void)
                reset_timeout();
                head_ref_namespaced(send_ref, &symref);
                for_each_namespaced_ref(send_ref, &symref);
+               advertise_shallow_grafts(1);
                packet_flush(1);
        } else {
                head_ref_namespaced(mark_our_ref, NULL);
@@ -835,8 +836,9 @@ int main(int argc, char **argv)
 
        if (!enter_repo(dir, strict))
                die("'%s' does not appear to be a git repository", dir);
-       if (is_repository_shallow())
-               die("attempt to fetch/clone from a shallow repository");
+       if (is_repository_shallow() && stateless_rpc)
+               die("attempt to push into a shallow repository");
+
        git_config(upload_pack_config, NULL);
        upload_pack();
        return 0;