gitformat-index(5)
==================

NAME
----
gitformat-index - Git index format

SYNOPSIS
--------
[verse]
$GIT_DIR/index

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

Git index format

== The Git index file has the following format

  All binary numbers are in network byte order.
  In a repository using the traditional SHA-1, checksums and object IDs
  (object names) mentioned below are all computed using SHA-1.  Similarly,
  in SHA-256 repositories, these values are computed using SHA-256.
  Version 2 is described here unless stated otherwise.

   - A 12-byte header consisting of

     4-byte signature:
       The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache")

     4-byte version number:
       The current supported versions are 2, 3 and 4.

     32-bit number of index entries.

   - A number of sorted index entries (see below).

   - Extensions

     Extensions are identified by signature. Optional extensions can
     be ignored if Git does not understand them.

     4-byte extension signature. If the first byte is 'A'..'Z' the
     extension is optional and can be ignored.

     32-bit size of the extension

     Extension data

   - Hash checksum over the content of the index file before this checksum.

== Index entry

  Index entries are sorted in ascending order on the name field,
  interpreted as a string of unsigned bytes (i.e. memcmp() order, no
  localization, no special casing of directory separator '/'). Entries
  with the same name are sorted by their stage field.

  An index entry typically represents a file. However, if sparse-checkout
  is enabled in cone mode (`core.sparseCheckoutCone` is enabled) and the
  `extensions.sparseIndex` extension is enabled, then the index may
  contain entries for directories outside of the sparse-checkout definition.
  These entries have mode `040000`, include the `SKIP_WORKTREE` bit, and
  the path ends in a directory separator.

  32-bit ctime seconds, the last time a file's metadata changed
    this is stat(2) data

  32-bit ctime nanosecond fractions
    this is stat(2) data

  32-bit mtime seconds, the last time a file's data changed
    this is stat(2) data

  32-bit mtime nanosecond fractions
    this is stat(2) data

  32-bit dev
    this is stat(2) data

  32-bit ino
    this is stat(2) data

  32-bit mode, split into (high to low bits)

    16-bit unused, must be zero

    4-bit object type
      valid values in binary are 1000 (regular file), 1010 (symbolic link)
      and 1110 (gitlink)

    3-bit unused, must be zero

    9-bit unix permission. Only 0755 and 0644 are valid for regular files.
    Symbolic links and gitlinks have value 0 in this field.

  32-bit uid
    this is stat(2) data

  32-bit gid
    this is stat(2) data

  32-bit file size
    This is the on-disk size from stat(2), truncated to 32-bit.

  Object name for the represented object

  A 16-bit 'flags' field split into (high to low bits)

    1-bit assume-valid flag

    1-bit extended flag (must be zero in version 2)

    2-bit stage (during merge)

    12-bit name length if the length is less than 0xFFF; otherwise 0xFFF
    is stored in this field.

  (Version 3 or later) A 16-bit field, only applicable if the
  "extended flag" above is 1, split into (high to low bits).

    1-bit reserved for future

    1-bit skip-worktree flag (used by sparse checkout)

    1-bit intent-to-add flag (used by "git add -N")

    13-bit unused, must be zero

  Entry path name (variable length) relative to top level directory
    (without leading slash). '/' is used as path separator. The special
    path components ".", ".." and ".git" (without quotes) are disallowed.
    Trailing slash is also disallowed.

    The exact encoding is undefined, but the '.' and '/' characters
    are encoded in 7-bit ASCII and the encoding cannot contain a NUL
    byte (iow, this is a UNIX pathname).

  (Version 4) In version 4, the entry path name is prefix-compressed
    relative to the path name for the previous entry (the very first