c553ca25bd
Pack index version 2 goes as follows: - 8 bytes of header with signature and version. - 256 entries of 4-byte first-level fan-out table. - Table of sorted 20-byte SHA1 records for each object in pack. - Table of 4-byte CRC32 entries for raw pack object data. - Table of 4-byte offset entries for objects in the pack if offset is representable with 31 bits or less, otherwise it is an index in the next table with top bit set. - Table of 8-byte offset entries indexed from previous table for offsets which are 32 bits or more (optional). - 20-byte SHA1 checksum of sorted object names. - 20-byte SHA1 checksum of the above. The object SHA1 table is all contiguous so future pack format that would contain this table directly won't require big changes to the code. It is also tighter for slightly better cache locality when looking up entries. Support for large packs exceeding 31 bits in size won't impose an index size bloat for packs within that range that don't need a 64-bit offset. And because newer objects which are likely to be the most frequently used are located at the beginning of the pack, they won't pay the 64-bit offset lookup at run time either even if the pack is large. Right now an index version 2 is created only when the biggest offset in a pack reaches 31 bits. It might be a good idea to always use index version 2 eventually to benefit from the CRC32 it contains when reusing pack data while repacking. [jc: with the "oops" fix to keep track of the last offset correctly] Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
//////////////////////////////////////////////////////////////// GIT - the stupid content tracker //////////////////////////////////////////////////////////////// "git" can mean anything, depending on your mood. - random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant. - stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang. - "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room. - "goddamn idiotic truckload of sh*t": when it breaks Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals. Git is an Open Source project covered by the GNU General Public License. It was originally written by Linus Torvalds with help of a group of hackers around the net. It is currently maintained by Junio C Hamano. Please read the file INSTALL for installation instructions. See Documentation/tutorial.txt to get started, then see Documentation/everyday.txt for a useful minimum set of commands, and "man git-commandname" for documentation of each command. CVS users may also want to read Documentation/cvs-migration.txt. Many Git online resources are accessible from http://git.or.cz/ including full documentation and Git related tools. The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org. To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at http://marc.theaimsgroup.com/?l=git and other archival sites. The messages titled "A note from the maintainer", "What's in git.git (stable)" and "What's cooking in git.git (topics)" and the discussion following them on the mailing list give a good reference for project status, development direction and remaining tasks.