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authorAlex Neronskiy <zakmagnus@google.com>2011-06-08 22:11:51 (GMT)
committerJunio C Hamano <gitster@pobox.com>2011-06-09 01:08:21 (GMT)
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Document the underlying protocol used by shallow repositories and --depth commands.
Explain the exchange that occurs between a client and server when the client is requesting shallow history and/or is already using a shallow repository. Signed-off-by: Alex Neronskiy <zakmagnus@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'Documentation/technical/pack-protocol.txt')
-rw-r--r--Documentation/technical/pack-protocol.txt88
1 files changed, 66 insertions, 22 deletions
diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt
index ce69f57..a7004c6 100644
--- a/Documentation/technical/pack-protocol.txt
+++ b/Documentation/technical/pack-protocol.txt
@@ -187,27 +187,28 @@ the client already is up-to-date.
Otherwise, it enters the negotiation phase, where the client and
server determine what the minimal packfile necessary for transport is,
-by telling the server what objects it wants and what objects it has,
-so the server can make a packfile that only contains the objects that the
-client needs. The client will also send a list of the capabilities it
-wants to be in effect, out of what the server said it could do with the
-first 'want' line.
+by telling the server what objects it wants, its shallow objects
+(if any), and the maximum commit depth it wants (if any). The client
+will also send a list of the capabilities it wants to be in effect,
+out of what the server said it could do with the first 'want' line.
----
upload-request = want-list
- have-list
- compute-end
+ *shallow-line
+ *1depth-request
+ flush-pkt
want-list = first-want
*additional-want
- flush-pkt
+
+ shallow-line = PKT_LINE("shallow" SP obj-id)
+
+ depth-request = PKT_LINE("deepen" SP depth)
first-want = PKT-LINE("want" SP obj-id SP capability-list LF)
additional-want = PKT-LINE("want" SP obj-id LF)
- have-list = *have-line
- have-line = PKT-LINE("have" SP obj-id LF)
- compute-end = flush-pkt / PKT-LINE("done")
+ depth = 1*DIGIT
----
Clients MUST send all the obj-ids it wants from the reference
@@ -216,21 +217,64 @@ discovery phase as 'want' lines. Clients MUST send at least one
obj-id in a 'want' command which did not appear in the response
obtained through ref discovery.
-If client is requesting a shallow clone, it will now send a 'deepen'
-line with the depth it is requesting.
+The client MUST write all obj-ids which it only has shallow copies
+of (meaning that it does not have the parents of a commit) as
+'shallow' lines so that the server is aware of the limitations of
+the client's history. Clients MUST NOT mention an obj-id which
+it does not know exists on the server.
+
+The client now sends the maximum commit history depth it wants for
+this transaction, which is the number of commits it wants from the
+tip of the history, if any, as a 'deepen' line. A depth of 0 is the
+same as not making a depth request. The client does not want to receive
+any commits beyond this depth, nor objects needed only to complete
+those commits. Commits whose parents are not received as a result are
+defined as shallow and marked as such in the server. This information
+is sent back to the client in the next step.
+
+Once all the 'want's and 'shallow's (and optional 'deepen') are
+transferred, clients MUST send a flush-pkt, to tell the server side
+that it is done sending the list.
+
+Otherwise, if the client sent a positive depth request, the server
+will determine which commits will and will not be shallow and
+send this information to the client. If the client did not request
+a positive depth, this step is skipped.
-Once all the "want"s (and optional 'deepen') are transferred,
-clients MUST send a flush-pkt, to tell the server side that it is
-done sending the list.
+----
+ shallow-update = *shallow-line
+ *unshallow-line
+ flush-pkt
-TODO: shallow/unshallow response and document the deepen command in the ABNF.
+ shallow-line = PKT-LINE("shallow" SP obj-id)
+
+ unshallow-line = PKT-LINE("unshallow" SP obj-id)
+----
+
+If the client has requested a positive depth, the server will compute
+the set of commits which are no deeper than the desired depth, starting
+at the client's wants. The server writes 'shallow' lines for each
+commit whose parents will not be sent as a result. The server writes
+an 'unshallow' line for each commit which the client has indicated is
+shallow, but is no longer shallow at the currently requested depth
+(that is, its parents will now be sent). The server MUST NOT mark
+as unshallow anything which the client has not indicated was shallow.
Now the client will send a list of the obj-ids it has using 'have'
-lines. In multi_ack mode, the canonical implementation will send up
-to 32 of these at a time, then will send a flush-pkt. The canonical
-implementation will skip ahead and send the next 32 immediately,
-so that there is always a block of 32 "in-flight on the wire" at a
-time.
+lines, so the server can make a packfile that only contains the objects
+that the client needs. In multi_ack mode, the canonical implementation
+will send up to 32 of these at a time, then will send a flush-pkt. The
+canonical implementation will skip ahead and send the next 32 immediately,
+so that there is always a block of 32 "in-flight on the wire" at a time.
+
+----
+ upload-haves = have-list
+ compute-end
+
+ have-list = *have-line
+ have-line = PKT-LINE("have" SP obj-id LF)
+ compute-end = flush-pkt / PKT-LINE("done")
+----
If the server reads 'have' lines, it then will respond by ACKing any
of the obj-ids the client said it had that the server also has. The