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Junio C Hamano
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Merge branch 'kh/svn' into next
* kh/svn: git-svnimport: Don't assume that copied files haven't changed Add Documentation/technical/pack-format.txt Added Packing Heursitics IRC writeup. Add documentation for git-imap-send.
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‎Documentation/git-imap-send.txt‎

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git-imap-send(1)
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================
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NAME
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----
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git-imap-send - Dump a mailbox from stdin into an imap folder
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SYNOPSIS
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--------
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'git-imap-send'
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DESCRIPTION
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-----------
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This command uploads a mailbox generated with git-format-patch
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into an imap drafts folder. This allows patches to be sent as
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other email is sent with mail clients that cannot read mailbox
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files directly.
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Typical usage is something like:
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git-format-patch --signoff --stdout --attach origin | git-imap-send
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CONFIGURATION
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-------------
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git-imap-send requires the following values in the repository
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configuration file (shown with examples):
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[imap]
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Folder = "INBOX.Drafts"
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[imap]
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Tunnel = "ssh -q user@server.com /usr/bin/imapd ./Maildir 2> /dev/null"
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[imap]
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Host = imap.server.com
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User = bob
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Password = pwd
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Port = 143
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BUGS
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----
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Doesn't handle lines starting with "From " in the message body.
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Author
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------
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Derived from isync 1.0.1 by Mike McCormack.
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Documentation
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--------------
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Documentation by Mike McCormack
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GIT
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---
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Part of the gitlink:git[7] suite

‎Documentation/technical/pack-format.txt‎

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GIT pack format
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===============
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= pack-*.pack file has the following format:
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- The header appears at the beginning and consists of the following:
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4-byte signature
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4-byte version number (network byte order)
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4-byte number of objects contained in the pack (network byte order)
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Observation: we cannot have more than 4G versions ;-) and
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more than 4G objects in a pack.
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- The header is followed by number of object entries, each of
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which looks like this:
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(undeltified representation)
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n-byte type and length (4-bit type, (n-1)*7+4-bit length)
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compressed data
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(deltified representation)
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n-byte type and length (4-bit type, (n-1)*7+4-bit length)
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20-byte base object name
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compressed delta data
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Observation: length of each object is encoded in a variable
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length format and is not constrained to 32-bit or anything.
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- The trailer records 20-byte SHA1 checksum of all of the above.
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= pack-*.idx file has the following format:
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- The header consists of 256 4-byte network byte order
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integers. N-th entry of this table records the number of
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objects in the corresponding pack, the first byte of whose
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object name are smaller than N. This is called the
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'first-level fan-out' table.
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Observation: we would need to extend this to an array of
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8-byte integers to go beyond 4G objects per pack, but it is
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not strictly necessary.
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- The header is followed by sorted 28-byte entries, one entry
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per object in the pack. Each entry is:
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4-byte network byte order integer, recording where the
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object is stored in the packfile as the offset from the
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beginning.
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20-byte object name.
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Observation: we would definitely need to extend this to
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8-byte integer plus 20-byte object name to handle a packfile
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that is larger than 4GB.
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- The file is concluded with a trailer:
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A copy of the 20-byte SHA1 checksum at the end of
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corresponding packfile.
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20-byte SHA1-checksum of all of the above.
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Pack Idx file:
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idx
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+--------------------------------+
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| fanout[0] = 2 |-.
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+--------------------------------+ |
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| fanout[1] | |
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+--------------------------------+ |
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| fanout[2] | |
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
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| fanout[255] | |
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+--------------------------------+ |
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main | offset | |
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index | object name 00XXXXXXXXXXXXXXXX | |
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table +--------------------------------+ |
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| offset | |
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| object name 00XXXXXXXXXXXXXXXX | |
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+--------------------------------+ |
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.-| offset |<+
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| | object name 01XXXXXXXXXXXXXXXX |
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| +--------------------------------+
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| | offset |
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| | object name 01XXXXXXXXXXXXXXXX |
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| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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| | offset |
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| | object name FFXXXXXXXXXXXXXXXX |
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| +--------------------------------+
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trailer | | packfile checksum |
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| +--------------------------------+
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| | idxfile checksum |
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| +--------------------------------+
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.-------.
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|
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Pack file entry: <+
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packed object header:
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1-byte type (upper 4-bit)
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size0 (lower 4-bit)
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n-byte sizeN (as long as MSB is set, each 7-bit)
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size0..sizeN form 4+7+7+..+7 bit integer, size0
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is the most significant part.
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packed object data:
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If it is not DELTA, then deflated bytes (the size above
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is the size before compression).
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If it is DELTA, then
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20-byte base object name SHA1 (the size above is the
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size of the delta data that follows).
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delta data, deflated.

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