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-rw-r--r--Documentation/technical/index-format.txt34
1 files changed, 24 insertions, 10 deletions
diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt
index 8930b3fabc..f352a9b22e 100644
--- a/Documentation/technical/index-format.txt
+++ b/Documentation/technical/index-format.txt
@@ -1,7 +1,7 @@
-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.
@@ -12,7 +12,7 @@ GIT index format
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.
@@ -21,9 +21,9 @@ GIT index format
- 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.
@@ -93,8 +93,8 @@ GIT index format
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
@@ -113,9 +113,22 @@ GIT index format
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.
+
== Extensions
=== Cached tree
@@ -148,8 +161,9 @@ GIT index format
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
@@ -161,7 +175,7 @@ GIT index format
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