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Diffstat (limited to 'Documentation/technical/protocol-capabilities.txt')
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 31 |
1 files changed, 23 insertions, 8 deletions
diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index fd8ffa5df3..e3e792476e 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -72,14 +72,29 @@ interleaved with S-R-Q. thin-pack --------- -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 |