This bases on the original work by Robin Rosenberg: http://thread.gmane.org/gmane.comp.version-control.git/73471 Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> --- I split index entry out so the overall format is clearer. Other changes: - mention of version 3 - added ino and mode - added extended flags (v3) - entry sort order Again I don't realy know REUC extension, so only placeholder Documentation/technical/index-format.txt | 139 ++++++++++++++++++++++++++++++ 1 files changed, 139 insertions(+), 0 deletions(-) create mode 100644 Documentation/technical/index-format.txt diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt new file mode 100644 index 0000000..3e113ca --- /dev/null +++ b/Documentation/technical/index-format.txt @@ -0,0 +1,139 @@ +GIT index 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. + + - A 12-byte header consisting of + + 4-byte signature: + The signature is { 'D', 'I', 'R', 'C' } + + 4-byte version number: + The current supported versions are 2 and 3. + + 32-bit number of index entries. + + - A number of sorted index entries + + - Extensions + + Extensions are identified by signature. Optional extensions can + be ignored if GIT does not understand them. + + GIT currently supports tree cache and resolve undo extensions. + + 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 + + - 160-bit SHA-1 over the content of the index file before this + checksum. + +== Index entry + + Index entries are sorted with memcmp() by entry name. Entries with + the same name are sorted by their stage. + + 32-bit ctime seconds, the last time a file's metadata changed + this is stat(2) data + + 32-bit ctime nanoseconds (modulo 1G) + 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 nanoseconds (modulo 1G) + 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) + + 4-bit object type + valid values in binary are 1000 (blob), 1010 (symbolic link) + and 1110 (gitlink) + + 3-bit unused + + 9-bit unix permission (only 0755 and 0644 are valid) + + 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) + + 160-bit SHA-1 for the represented object + + A 16-bit 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 0x0FFF + + (Version 3) 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. Special + paths ".", ".." and ".git" (without quotes) are disallowed. + Trailing slash is also disallowed. + + 1-8 nul bytes as necessary to pad the entry to a multiple ot eight bytes + while keeping the name NUL-terminated. + +== Extensions + +=== Tree cache + + Tree cache extension contains pre-computes hashes for all trees that + can be derived from the index + + - Extension tag { 'T', 'R', 'E', 'E' } + + - 32-bit size + + - A number of entries + + NUL-terminated tree name + + Blank-terminated ASCII decimal number of entries in this tree + + Newline-terminated position of this tree in the parent tree. 0 for + the root tree + + 160-bit SHA-1 for this tree and it's children + +=== Resolve undo + + TODO + + - Extension tag { 'R', 'E', 'U', 'C' } + + - 32-bit size -- 1.7.1.rc1.69.g24c2f7 -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html