diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/bitmap-format.txt | 71 | ||||
| -rw-r--r-- | Documentation/technical/http-protocol.txt | 3 | ||||
| -rw-r--r-- | Documentation/technical/multi-pack-index.txt | 10 | ||||
| -rw-r--r-- | Documentation/technical/protocol-v2.txt | 17 |
5 files changed, 78 insertions, 28 deletions
diff --git a/Documentation/technical/api-parse-options.txt b/Documentation/technical/api-parse-options.txt index 5a60bbfa7f..acfd5dc1d8 100644 --- a/Documentation/technical/api-parse-options.txt +++ b/Documentation/technical/api-parse-options.txt @@ -198,11 +198,6 @@ There are some macros to easily define options: The filename will be prefixed by passing the filename along with the prefix argument of `parse_options()` to `prefix_filename()`. -`OPT_ARGUMENT(long, &int_var, description)`:: - Introduce a long-option argument that will be kept in `argv[]`. - If this option was seen, `int_var` will be set to one (except - if a `NULL` pointer was passed). - `OPT_NUMBER_CALLBACK(&var, description, func_ptr)`:: Recognize numerical options like -123 and feed the integer as if it was an argument to the function given by `func_ptr`. diff --git a/Documentation/technical/bitmap-format.txt b/Documentation/technical/bitmap-format.txt index f8c18a0f7a..04b3ec2178 100644 --- a/Documentation/technical/bitmap-format.txt +++ b/Documentation/technical/bitmap-format.txt @@ -1,6 +1,44 @@ GIT bitmap v1 format ==================== +== Pack and multi-pack bitmaps + +Bitmaps store reachability information about the set of objects in a packfile, +or a multi-pack index (MIDX). The former is defined obviously, and the latter is +defined as the union of objects in packs contained in the MIDX. + +A bitmap may belong to either one pack, or the repository's multi-pack index (if +it exists). A repository may have at most one bitmap. + +An object is uniquely described by its bit position within a bitmap: + + - If the bitmap belongs to a packfile, the __n__th bit corresponds to + the __n__th object in pack order. For a function `offset` which maps + objects to their byte offset within a pack, pack order is defined as + follows: + + o1 <= o2 <==> offset(o1) <= offset(o2) + + - If the bitmap belongs to a MIDX, the __n__th bit corresponds to the + __n__th object in MIDX order. With an additional function `pack` which + maps objects to the pack they were selected from by the MIDX, MIDX order + is defined as follows: + + o1 <= o2 <==> pack(o1) <= pack(o2) /\ offset(o1) <= offset(o2) + + The ordering between packs is done according to the MIDX's .rev file. + Notably, the preferred pack sorts ahead of all other packs. + +The on-disk representation (described below) of a bitmap is the same regardless +of whether or not that bitmap belongs to a packfile or a MIDX. The only +difference is the interpretation of the bits, which is described above. + +Certain bitmap extensions are supported (see: Appendix B). No extensions are +required for bitmaps corresponding to packfiles. For bitmaps that correspond to +MIDXs, both the bit-cache and rev-cache extensions are required. + +== On-disk format + - A header appears at the beginning: 4-byte signature: {'B', 'I', 'T', 'M'} @@ -14,17 +52,19 @@ GIT bitmap v1 format The following flags are supported: - BITMAP_OPT_FULL_DAG (0x1) REQUIRED - This flag must always be present. It implies that the bitmap - index has been generated for a packfile with full closure - (i.e. where every single object in the packfile can find - its parent links inside the same packfile). This is a - requirement for the bitmap index format, also present in JGit, - that greatly reduces the complexity of the implementation. + This flag must always be present. It implies that the + bitmap index has been generated for a packfile or + multi-pack index (MIDX) with full closure (i.e. where + every single object in the packfile/MIDX can find its + parent links inside the same packfile/MIDX). This is a + requirement for the bitmap index format, also present in + JGit, that greatly reduces the complexity of the + implementation. - BITMAP_OPT_HASH_CACHE (0x4) If present, the end of the bitmap file contains `N` 32-bit name-hash values, one per object in the - pack. The format and meaning of the name-hash is + pack/MIDX. The format and meaning of the name-hash is described below. 4-byte entry count (network byte order) @@ -33,7 +73,8 @@ GIT bitmap v1 format 20-byte checksum - The SHA1 checksum of the pack this bitmap index belongs to. + The SHA1 checksum of the pack/MIDX this bitmap index + belongs to. - 4 EWAH bitmaps that act as type indexes @@ -50,7 +91,7 @@ GIT bitmap v1 format - Tags In each bitmap, the `n`th bit is set to true if the `n`th object - in the packfile is of that type. + in the packfile or multi-pack index is of that type. The obvious consequence is that the OR of all 4 bitmaps will result in a full set (all bits set), and the AND of all 4 bitmaps will @@ -62,8 +103,9 @@ GIT bitmap v1 format Each entry contains the following: - 4-byte object position (network byte order) - The position **in the index for the packfile** where the - bitmap for this commit is found. + The position **in the index for the packfile or + multi-pack index** where the bitmap for this commit is + found. - 1-byte XOR-offset The xor offset used to compress this bitmap. For an entry @@ -146,10 +188,11 @@ Name-hash cache --------------- If the BITMAP_OPT_HASH_CACHE flag is set, the end of the bitmap contains -a cache of 32-bit values, one per object in the pack. The value at +a cache of 32-bit values, one per object in the pack/MIDX. The value at position `i` is the hash of the pathname at which the `i`th object -(counting in index order) in the pack can be found. This can be fed -into the delta heuristics to compare objects with similar pathnames. +(counting in index or multi-pack index order) in the pack/MIDX can be found. +This can be fed into the delta heuristics to compare objects with similar +pathnames. The hash algorithm used is: diff --git a/Documentation/technical/http-protocol.txt b/Documentation/technical/http-protocol.txt index 96d89ea9b2..cc5126cfed 100644 --- a/Documentation/technical/http-protocol.txt +++ b/Documentation/technical/http-protocol.txt @@ -225,6 +225,9 @@ The client may send Extra Parameters (see Documentation/technical/pack-protocol.txt) as a colon-separated string in the Git-Protocol HTTP header. +Uses the `--http-backend-info-refs` option to +linkgit:git-upload-pack[1]. + Dumb Server Response ^^^^^^^^^^^^^^^^^^^^ Dumb servers MUST respond with the dumb server reply format. diff --git a/Documentation/technical/multi-pack-index.txt b/Documentation/technical/multi-pack-index.txt index fb688976c4..1a73c3ee20 100644 --- a/Documentation/technical/multi-pack-index.txt +++ b/Documentation/technical/multi-pack-index.txt @@ -71,14 +71,10 @@ Future Work still reducing the number of binary searches required for object lookups. -- The reachability bitmap is currently paired directly with a single - packfile, using the pack-order as the object order to hopefully - compress the bitmaps well using run-length encoding. This could be - extended to pair a reachability bitmap with a multi-pack-index. If - the multi-pack-index is extended to store a "stable object order" +- If the multi-pack-index is extended to store a "stable object order" (a function Order(hash) = integer that is constant for a given hash, - even as the multi-pack-index is updated) then a reachability bitmap - could point to a multi-pack-index and be updated independently. + even as the multi-pack-index is updated) then MIDX bitmaps could be + updated independently of the MIDX. - Packfiles can be marked as "special" using empty files that share the initial name but replace ".pack" with ".keep" or ".promisor". diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt index 1040d85319..21e8258ccf 100644 --- a/Documentation/technical/protocol-v2.txt +++ b/Documentation/technical/protocol-v2.txt @@ -42,7 +42,8 @@ Initial Client Request In general a client can request to speak protocol v2 by sending `version=2` through the respective side-channel for the transport being used which inevitably sets `GIT_PROTOCOL`. More information can be -found in `pack-protocol.txt` and `http-protocol.txt`. In all cases the +found in `pack-protocol.txt` and `http-protocol.txt`, as well as the +`GIT_PROTOCOL` definition in `git.txt`. In all cases the response from the server is the capability advertisement. Git Transport @@ -58,6 +59,8 @@ SSH and File Transport When using either the ssh:// or file:// transport, the GIT_PROTOCOL environment variable must be set explicitly to include "version=2". +The server may need to be configured to allow this environment variable +to pass. HTTP Transport ~~~~~~~~~~~~~~ @@ -81,6 +84,12 @@ A v2 server would reply: Subsequent requests are then made directly to the service `$GIT_URL/git-upload-pack`. (This works the same for git-receive-pack). +Uses the `--http-backend-info-refs` option to +linkgit:git-upload-pack[1]. + +The server may need to be configured to pass this header's contents via +the `GIT_PROTOCOL` variable. See the discussion in `git-http-backend.txt`. + Capability Advertisement ------------------------ @@ -190,7 +199,11 @@ ls-refs takes in the following arguments: Show peeled tags. ref-prefix <prefix> When specified, only references having a prefix matching one of - the provided prefixes are displayed. + the provided prefixes are displayed. Multiple instances may be + given, in which case references matching any prefix will be + shown. Note that this is purely for optimization; a server MAY + show refs not matching the prefix if it chooses, and clients + should filter the result themselves. If the 'unborn' feature is advertised the following argument can be included in the client's request. |