-GIT index format
+Git index format
================
-= The git index file has the following format
+== The Git index file has the following format
All binary numbers are in network byte order. Version 2 is described
here unless stated otherwise.
The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache")
4-byte version number:
- The current supported versions are 2 and 3.
+ The current supported versions are 2, 3 and 4.
32-bit number of index entries.
- Extensions
Extensions are identified by signature. Optional extensions can
- be ignored if GIT does not understand them.
+ be ignored if Git does not understand them.
- GIT currently supports cached tree and resolve undo extensions.
+ Git currently supports cached tree and resolve undo extensions.
4-byte extension signature. If the first byte is 'A'..'Z' the
extension is optional and can be ignored.
12-bit name length if the length is less than 0xFFF; otherwise 0xFFF
is stored in this field.
- (Version 3) A 16-bit field, only applicable if the "extended flag"
- above is 1, split into (high to low bits).
+ (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
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
+ entry is encoded as if the path name for the previous entry is an
+ empty string). At the beginning of an entry, an integer N in the
+ variable width encoding (the same encoding as the offset is encoded
+ for OFS_DELTA pack entries; see pack-format.txt) is stored, followed
+ by a NUL-terminated string S. Removing N bytes from the end of the
+ path name for the previous entry, and replacing it with the string S
+ yields the path name for this entry.
+
1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes
while keeping the name NUL-terminated.
+ (Version 4) In version 4, the padding after the pathname does not
+ exist.
+
+ Interpretation of index entries in split index mode is completely
+ different. See below for details.
+
== Extensions
=== Cached tree
this span of index as a tree.
An entry can be in an invalidated state and is represented by having
- -1 in the entry_count field. In this case, there is no object name
- and the next entry starts immediately after the newline.
+ a negative number in the entry_count field. In this case, there is no
+ object name and the next entry starts immediately after the newline.
+ When writing an invalid entry, -1 should always be used as entry_count.
The entries are written out in the top-down, depth-first order. The
first entry represents the root level of the repository, followed by the
A conflict is represented in the index as a set of higher stage entries.
When a conflict is resolved (e.g. with "git add path"), these higher
- stage entries will be removed and a stage-0 entry with proper resoluton
+ stage entries will be removed and a stage-0 entry with proper resolution
is added.
When these higher stage entries are removed, they are saved in the
- At most three 160-bit object names of the entry in stages from 1 to 3
(nothing is written for a missing stage).
+=== Split index
+
+ In split index mode, the majority of index entries could be stored
+ in a separate file. This extension records the changes to be made on
+ top of that to produce the final index.
+
+ The signature for this extension is { 'l', 'i', 'n', 'k' }.
+
+ The extension consists of:
+
+ - 160-bit SHA-1 of the shared index file. The shared index file path
+ is $GIT_DIR/sharedindex.<SHA-1>. If all 160 bits are zero, the
+ index does not require a shared index file.
+
+ - An ewah-encoded delete bitmap, each bit represents an entry in the
+ shared index. If a bit is set, its corresponding entry in the
+ shared index will be removed from the final index. Note, because
+ a delete operation changes index entry positions, but we do need
+ original positions in replace phase, it's best to just mark
+ entries for removal, then do a mass deletion after replacement.
+
+ - An ewah-encoded replace bitmap, each bit represents an entry in
+ the shared index. If a bit is set, its corresponding entry in the
+ shared index will be replaced with an entry in this index
+ file. All replaced entries are stored in sorted order in this
+ index. The first "1" bit in the replace bitmap corresponds to the
+ first index entry, the second "1" bit to the second entry and so
+ on. Replaced entries may have empty path names to save space.
+
+ The remaining index entries after replaced ones will be added to the
+ final index. These added entries are also sorted by entry name then
+ stage.
+
+== Untracked cache
+
+ Untracked cache saves the untracked file list and necessary data to
+ verify the cache. The signature for this extension is { 'U', 'N',
+ 'T', 'R' }.
+
+ The extension starts with
+
+ - A sequence of NUL-terminated strings, preceded by the size of the
+ sequence in variable width encoding. Each string describes the
+ environment where the cache can be used.
+
+ - Stat data of $GIT_DIR/info/exclude. See "Index entry" section from
+ ctime field until "file size".
+
+ - Stat data of core.excludesfile
+
+ - 32-bit dir_flags (see struct dir_struct)
+
+ - 160-bit SHA-1 of $GIT_DIR/info/exclude. Null SHA-1 means the file
+ does not exist.
+
+ - 160-bit SHA-1 of core.excludesfile. Null SHA-1 means the file does
+ not exist.
+
+ - NUL-terminated string of per-dir exclude file name. This usually
+ is ".gitignore".
+
+ - The number of following directory blocks, variable width
+ encoding. If this number is zero, the extension ends here with a
+ following NUL.
+
+ - A number of directory blocks in depth-first-search order, each
+ consists of
+
+ - The number of untracked entries, variable width encoding.
+
+ - The number of sub-directory blocks, variable width encoding.
+
+ - The directory name terminated by NUL.
+
+ - A number of untracked file/dir names terminated by NUL.
+
+The remaining data of each directory block is grouped by type:
+
+ - An ewah bitmap, the n-th bit marks whether the n-th directory has
+ valid untracked cache entries.
+
+ - An ewah bitmap, the n-th bit records "check-only" bit of
+ read_directory_recursive() for the n-th directory.
+
+ - An ewah bitmap, the n-th bit indicates whether SHA-1 and stat data
+ is valid for the n-th directory and exists in the next data.
+
+ - An array of stat data. The n-th data corresponds with the n-th
+ "one" bit in the previous ewah bitmap.
+
+ - An array of SHA-1. The n-th SHA-1 corresponds with the n-th "one" bit
+ in the previous ewah bitmap.
+
+ - One NUL.
projects / platform / upstream / git.git / blobdiff