368dc5d6ae
Signed-off-by: Thomas Ackermann <th.acker@arcor.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
64 lines
1.9 KiB
Plaintext
64 lines
1.9 KiB
Plaintext
Git-send-pack internals
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=======================
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Overall operation
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-----------------
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. Connects to the remote side and invokes git-receive-pack.
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. Learns what refs the remote has and what commit they point at.
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Matches them to the refspecs we are pushing.
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. Checks if there are non-fast-forwards. Unlike fetch-pack,
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the repository send-pack runs in is supposed to be a superset
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of the recipient in fast-forward cases, so there is no need
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for want/have exchanges, and fast-forward check can be done
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locally. Tell the result to the other end.
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. Calls pack_objects() which generates a packfile and sends it
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over to the other end.
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. If the remote side is new enough (v1.1.0 or later), wait for
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the unpack and hook status from the other end.
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. Exit with appropriate error codes.
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Pack_objects pipeline
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---------------------
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This function gets one file descriptor (`fd`) which is either a
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socket (over the network) or a pipe (local). What's written to
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this fd goes to git-receive-pack to be unpacked.
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send-pack ---> fd ---> receive-pack
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The function pack_objects creates a pipe and then forks. The
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forked child execs pack-objects with --revs to receive revision
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parameters from its standard input. This process will write the
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packfile to the other end.
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send-pack
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pack_objects() ---> fd ---> receive-pack
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| ^ (pipe)
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v |
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(child)
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The child dup2's to arrange its standard output to go back to
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the other end, and read its standard input to come from the
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pipe. After that it exec's pack-objects. On the other hand,
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the parent process, before starting to feed the child pipeline,
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closes the reading side of the pipe and fd to receive-pack.
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send-pack
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pack_objects(parent)
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v [0]
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pack-objects [0] ---> receive-pack
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[jc: the pipeline was much more complex and needed documentation before
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I understood an earlier bug, but now it is trivial and straightforward.]
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