diff options
| -rw-r--r-- | Documentation/technical/index-format.txt | 94 |
1 files changed, 57 insertions, 37 deletions
diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt index 89e410a8b..7b233ca19 100644 --- a/Documentation/technical/index-format.txt +++ b/Documentation/technical/index-format.txt @@ -9,21 +9,21 @@ GIT index format - A 12-byte header consisting of 4-byte signature: - The signature is { 'D', 'I', 'R', 'C' } + The signature is { 'D', 'I', 'R', 'C' } (stands for "dircache") 4-byte version number: The current supported versions are 2 and 3. 32-bit number of index entries. - - A number of sorted 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. - GIT currently supports tree cache 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. @@ -38,8 +38,9 @@ GIT index format == Index entry Index entries are sorted in ascending order on the name field, - interpreted as a string of unsigned bytes. Entries with the same - name are sorted by their stage 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. 32-bit ctime seconds, the last time a file's metadata changed this is stat(2) data @@ -62,12 +63,13 @@ GIT index format 32-bit mode, split into (high to low bits) 4-bit object type - valid values in binary are 1000 (blob), 1010 (symbolic link) + valid values in binary are 1000 (regular file), 1010 (symbolic link) and 1110 (gitlink) 3-bit unused - 9-bit unix permission (only 0755 and 0644 are valid) + 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 @@ -76,11 +78,11 @@ GIT index format this is stat(2) data 32-bit file size - This is the on-disk size from stat(2) + This is the on-disk size from stat(2), truncated to 32-bit. 160-bit SHA-1 for the represented object - A 16-bit field split into (high to low bits) + A 16-bit 'flags' field split into (high to low bits) 1-bit assume-valid flag @@ -88,7 +90,8 @@ GIT index format 2-bit stage (during merge) - 12-bit name length if the length is less than 0x0FFF + 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). @@ -103,63 +106,80 @@ GIT index format Entry path name (variable length) relative to top level directory (without leading slash). '/' is used as path separator. The special - paths ".", ".." and ".git" (without quotes) are disallowed. + 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. Generally a superset of ASCII. + are encoded in 7-bit ASCII and the encoding cannot contain a NUL + byte (iow, this is a UNIX pathname). 1-8 nul bytes as necessary to pad the entry to a multiple of eight bytes while keeping the name NUL-terminated. == Extensions -=== Tree cache +=== Cached tree - Tree cache extension contains pre-computed hashes for trees that can + Cached tree extension contains pre-computed hashes for trees that can be derived from the index. It helps speed up tree object generation from index for a new commit. When a path is updated in index, the path must be invalidated and removed from tree cache. - - Extension tag { 'T', 'R', 'E', 'E' } + The signature for this extension is { 'T', 'R', 'E', 'E' }. - - 32-bit size + A series of entries fill the entire extension; each of which + consists of: - - A number of entries + - NUL-terminated path component (relative to its parent directory); - NUL-terminated tree name + - ASCII decimal number of entries in the index that is covered by the + tree this entry represents (entry_count); - Blank-terminated ASCII decimal number of entries in this tree + - A space (ASCII 32); - Newline-terminated position of this tree in the parent tree. 0 for - the root tree + - ASCII decimal number that represents the number of subtrees this + tree has; - 160-bit SHA-1 for this tree and it's children + - A newline (ASCII 10); and + + - 160-bit object name for the object that would result from writing + 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. + + 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 + first subtree---let's call this A---of the root level (with its name + relative to the root level), followed by the first subtree of A (with + its name relative to A), ... === Resolve undo - A conflict is represented in index as a set of higher stage entries. + 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 is added. + stage entries will be removed and a stage-0 entry with proper resoluton + is added. - Resolve undo extension saves these higher stage entries so that - conflicts can be recreated (e.g. with "git checkout -m"), in case - users want to redo a conflict resolution from scratch. + When these higher stage entries are removed, they are saved in the + resolve undo extension, so that conflicts can be recreated (e.g. with + "git checkout -m"), in case users want to redo a conflict resolution + from scratch. - - Extension tag { 'R', 'E', 'U', 'C' } + The signature for this extension is { 'R', 'E', 'U', 'C' }. - - 32-bit size + A series of entries fill the entire extension; each of which + consists of: - - A number of conflict entries + - NUL-terminated pathname the entry describes (relative to the root of + the repository, i.e. full pathname); - NUL-terminated conflict path + - Three NUL-terminated ASCII octal numbers, entry mode of entries in + stage 1 to 3 (a missing stage is represented by "0" in this field); + and - Three NUL-terminated ASCII octal numbers, entry mode of entries in - stage 1 to 3. + - At most three 160-bit object names of the entry in stages from 1 to 3 + (nothing is written for a missing stage). - At most three 160-bit SHA-1s of the entry in three stages from 1 - to 3. SHA-1 is not saved for any stage with entry mode zero. |