Documentation/gitformat-loose.adoc

gitformat-loose(5)
==================

NAME
----
gitformat-loose - Git loose object format


SYNOPSIS
--------
[verse]
$GIT_DIR/objects/[0-9a-f][0-9a-f]/*

DESCRIPTION
-----------

Loose objects are how Git stores individual objects, where every object is
written as a separate file.

Over the lifetime of a repository, objects are usually written as loose objects
initially.  Eventually, these loose objects will be compacted into packfiles
via repository maintenance to improve disk space usage and speed up the lookup
of these objects.

== Loose objects

Each loose object contains a prefix, followed immediately by the data of the
object.  The prefix contains `<type> <size>\0`.  `<type>` is one of `blob`,
`tree`, `commit`, or `tag` and `size` is the size of the data (without the
prefix) as a decimal integer expressed in ASCII.

The entire contents, prefix and data concatenated, is then compressed with zlib
and the compressed data is stored in the file.  The object ID of the object is
the SHA-1 or SHA-256 (as appropriate) hash of the uncompressed data.

The file for the loose object is stored under the `objects` directory, with the
first two hex characters of the object ID being the directory and the remaining
characters being the file name.  This is done to shard the data and avoid too
many files being in one directory, since some file systems perform poorly with
many items in a directory.

As an example, the empty tree contains the data (when uncompressed) `tree 0\0`
and, in a SHA-256 repository, would have the object ID
`6ef19b41225c5369f1c104d45d8d85efa9b057b53b14b4b9b939dd74decc5321` and would be
stored under
`$GIT_DIR/objects/6e/f19b41225c5369f1c104d45d8d85efa9b057b53b14b4b9b939dd74decc5321`.

Similarly, a blob containing the contents `abc` would have the uncompressed
data of `blob 3\0abc`.

GIT
---
Part of the linkgit:git[1] suite