path: root/Documentation/technical
diff options
authorCarlos Martín Nieto <>2013-11-23 16:07:55 (GMT)
committerJunio C Hamano <>2013-11-25 21:16:19 (GMT)
commit1ba98a79f1b991e6f2b1d01ac392ba2edadc3ca1 (patch)
tree11c0b5f8bd0f9eb190bb4dca6682c2e53db52550 /Documentation/technical
parentf26f72de159d7ade2fbe8b48734ce98c1aba4d72 (diff)
send-pack: don't send a thin pack to a server which doesn't support it
Up to now git has assumed that all servers are able to fix thin packs. This is however not always the case. Document the 'no-thin' capability and prevent send-pack from generating a thin pack if the server advertises it. Signed-off-by: Carlos Martín Nieto <> Helped-by: Jeff King <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'Documentation/technical')
1 files changed, 23 insertions, 8 deletions
diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt
index fd8ffa5..e3e7924 100644
--- a/Documentation/technical/protocol-capabilities.txt
+++ b/Documentation/technical/protocol-capabilities.txt
@@ -72,14 +72,29 @@ interleaved with S-R-Q.
-This capability means that the server can send a 'thin' pack, a pack
-which does not contain base objects; if those base objects are available
-on client side. Client requests 'thin-pack' capability when it
-understands how to "thicken" it by adding required delta bases making
-it self-contained.
-Client MUST NOT request 'thin-pack' capability if it cannot turn a thin
-pack into a self-contained pack.
+A thin pack is one with deltas which reference base objects not
+contained within the pack (but are known to exist at the receiving
+end). This can reduce the network traffic significantly, but it
+requires the receiving end to know how to "thicken" these packs by
+adding the missing bases to the pack.
+The upload-pack server advertises 'thin-pack' when it can generate
+and send a thin pack. A client requests the 'thin-pack' capability
+when it understands how to "thicken" it, notifying the server that
+it can receive such a pack. A client MUST NOT request the
+'thin-pack' capability if it cannot turn a thin pack into a
+self-contained pack.
+Receive-pack, on the other hand, is assumed by default to be able to
+handle thin packs, but can ask the client not to use the feature by
+advertising the 'no-thin' capability. A client MUST NOT send a thin
+pack if the server advertises the 'no-thin' capability.
+The reasons for this asymmetry are historical. The receive-pack
+program did not exist until after the invention of thin packs, so
+historically the reference implementation of receive-pack always
+understood thin packs. Adding 'no-thin' later allowed receive-pack
+to disable the feature in a backwards-compatible manner.
side-band, side-band-64k