diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/commit-graph-format.txt | 9 | ||||
| -rw-r--r-- | Documentation/technical/commit-graph.txt | 6 | ||||
| -rw-r--r-- | Documentation/technical/hash-function-transition.txt | 2 | ||||
| -rw-r--r-- | Documentation/technical/http-protocol.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/index-format.txt | 34 | ||||
| -rw-r--r-- | Documentation/technical/pack-format.txt | 43 | ||||
| -rw-r--r-- | Documentation/technical/partial-clone.txt | 13 | ||||
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 12 | ||||
| -rw-r--r-- | Documentation/technical/shallow.txt | 2 |
9 files changed, 71 insertions, 55 deletions
diff --git a/Documentation/technical/commit-graph-format.txt b/Documentation/technical/commit-graph-format.txt index 440541045d..6ddbceba15 100644 --- a/Documentation/technical/commit-graph-format.txt +++ b/Documentation/technical/commit-graph-format.txt @@ -42,8 +42,13 @@ HEADER: 1-byte version number: Currently, the only valid version is 1. - 1-byte Hash Version (1 = SHA-1) - We infer the hash length (H) from this value. + 1-byte Hash Version + We infer the hash length (H) from this value: + 1 => SHA-1 + 2 => SHA-256 + If the hash type does not match the repository's hash algorithm, the + commit-graph file should be ignored with a warning presented to the + user. 1-byte number (C) of "chunks" diff --git a/Documentation/technical/commit-graph.txt b/Documentation/technical/commit-graph.txt index 808fa30b99..f14a7659aa 100644 --- a/Documentation/technical/commit-graph.txt +++ b/Documentation/technical/commit-graph.txt @@ -210,12 +210,12 @@ file. +---------------------+ | | +-----------------------+ +---------------------+ - | graph-{hash2} |->| | + | graph-{hash2} |->| | +-----------------------+ +---------------------+ | | | +-----------------------+ +---------------------+ | | | | - | graph-{hash1} |->| | + | graph-{hash1} |->| | | | | | +-----------------------+ +---------------------+ | tmp_graphXXX @@ -223,7 +223,7 @@ file. | | | | | | - | graph-{hash0} | + | graph-{hash0} | | | | | | | diff --git a/Documentation/technical/hash-function-transition.txt b/Documentation/technical/hash-function-transition.txt index 5b2db3be1e..6fd20ebbc2 100644 --- a/Documentation/technical/hash-function-transition.txt +++ b/Documentation/technical/hash-function-transition.txt @@ -650,7 +650,6 @@ Some initial steps can be implemented independently of one another: The first user-visible change is the introduction of the objectFormat extension (without compatObjectFormat). This requires: -- implementing the loose-object-idx - teaching fsck about this mode of operation - using the hash function API (vtable) when computing object names - signing objects and verifying signatures @@ -658,6 +657,7 @@ extension (without compatObjectFormat). This requires: repository Next comes introduction of compatObjectFormat: +- implementing the loose-object-idx - translating object names between object formats - translating object content between object formats - generating and verifying signatures in the compat format diff --git a/Documentation/technical/http-protocol.txt b/Documentation/technical/http-protocol.txt index 51a79e63de..96d89ea9b2 100644 --- a/Documentation/technical/http-protocol.txt +++ b/Documentation/technical/http-protocol.txt @@ -401,8 +401,9 @@ at all in the request stream: The stream is terminated by a pkt-line flush (`0000`). A single "want" or "have" command MUST have one hex formatted -SHA-1 as its value. Multiple SHA-1s MUST be sent by sending -multiple commands. +object name as its value. Multiple object names MUST be sent by sending +multiple commands. Object names MUST be given using the object format +negotiated through the `object-format` capability (default SHA-1). The `have` list is created by popping the first 32 commits from `c_pending`. Less can be supplied if `c_pending` empties. diff --git a/Documentation/technical/index-format.txt b/Documentation/technical/index-format.txt index faa25c5c52..f9a3644711 100644 --- a/Documentation/technical/index-format.txt +++ b/Documentation/technical/index-format.txt @@ -3,8 +3,11 @@ 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. + All binary numbers are in network byte order. + In a repository using the traditional SHA-1, checksums and object IDs + (object names) mentioned below are all computed using SHA-1. Similarly, + in SHA-256 repositories, these values are computed using SHA-256. + Version 2 is described here unless stated otherwise. - A 12-byte header consisting of @@ -32,8 +35,7 @@ Git index format Extension data - - 160-bit SHA-1 over the content of the index file before this - checksum. + - Hash checksum over the content of the index file before this checksum. == Index entry @@ -80,7 +82,7 @@ Git index format 32-bit file size This is the on-disk size from stat(2), truncated to 32-bit. - 160-bit SHA-1 for the represented object + Object name for the represented object A 16-bit 'flags' field split into (high to low bits) @@ -160,8 +162,8 @@ Git index format - A newline (ASCII 10); and - - 160-bit object name for the object that would result from writing - this span of index as a tree. + - 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 a negative number in the entry_count field. In this case, there is no @@ -198,7 +200,7 @@ Git index format stage 1 to 3 (a missing stage is represented by "0" in this field); and - - At most three 160-bit object names of the entry in stages from 1 to 3 + - At most three object names of the entry in stages from 1 to 3 (nothing is written for a missing stage). === Split index @@ -211,8 +213,8 @@ Git index format 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 + - Hash of the shared index file. The shared index file path + is $GIT_DIR/sharedindex.<hash>. If all bits are zero, the index does not require a shared index file. - An ewah-encoded delete bitmap, each bit represents an entry in the @@ -253,10 +255,10 @@ Git index format - 32-bit dir_flags (see struct dir_struct) - - 160-bit SHA-1 of $GIT_DIR/info/exclude. Null SHA-1 means the file + - Hash of $GIT_DIR/info/exclude. A null hash means the file does not exist. - - 160-bit SHA-1 of core.excludesfile. Null SHA-1 means the file does + - Hash of core.excludesfile. A null hash means the file does not exist. - NUL-terminated string of per-dir exclude file name. This usually @@ -285,13 +287,13 @@ The remaining data of each directory block is grouped by type: - 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 + - An ewah bitmap, the n-th bit indicates whether hash 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 + - An array of hashes. The n-th hash corresponds with the n-th "one" bit in the previous ewah bitmap. - One NUL. @@ -330,12 +332,12 @@ The remaining data of each directory block is grouped by type: - 32-bit offset to the end of the index entries - - 160-bit SHA-1 over the extension types and their sizes (but not + - Hash over the extension types and their sizes (but not their contents). E.g. if we have "TREE" extension that is N-bytes long, "REUC" extension that is M-bytes long, followed by "EOIE", then the hash would be: - SHA-1("TREE" + <binary representation of N> + + Hash("TREE" + <binary representation of N> + "REUC" + <binary representation of M>) == Index Entry Offset Table diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt index d3a142c652..f96b2e605f 100644 --- a/Documentation/technical/pack-format.txt +++ b/Documentation/technical/pack-format.txt @@ -1,6 +1,12 @@ Git pack format =============== +== Checksums and object IDs + +In a repository using the traditional SHA-1, pack checksums, index checksums, +and object IDs (object names) mentioned below are all computed using SHA-1. +Similarly, in SHA-256 repositories, these values are computed using SHA-256. + == pack-*.pack files have the following format: - A header appears at the beginning and consists of the following: @@ -26,7 +32,7 @@ Git pack format (deltified representation) n-byte type and length (3-bit type, (n-1)*7+4-bit length) - 20-byte base object name if OBJ_REF_DELTA or a negative relative + base object name if OBJ_REF_DELTA or a negative relative offset from the delta object's position in the pack if this is an OBJ_OFS_DELTA object compressed delta data @@ -34,7 +40,7 @@ Git pack format Observation: length of each object is encoded in a variable length format and is not constrained to 32-bit or anything. - - The trailer records 20-byte SHA-1 checksum of all of the above. + - The trailer records a pack checksum of all of the above. === Object types @@ -58,8 +64,8 @@ ofs-delta and ref-delta, which is only valid in a pack file. Both ofs-delta and ref-delta store the "delta" to be applied to another object (called 'base object') to reconstruct the object. The -difference between them is, ref-delta directly encodes 20-byte base -object name. If the base object is in the same pack, ofs-delta encodes +difference between them is, ref-delta directly encodes base object +name. If the base object is in the same pack, ofs-delta encodes the offset of the base object in the pack instead. The base object could also be deltified if it's in the same pack. @@ -143,14 +149,14 @@ This is the instruction reserved for future expansion. object is stored in the packfile as the offset from the beginning. - 20-byte object name. + one object name of the appropriate size. - The file is concluded with a trailer: - A copy of the 20-byte SHA-1 checksum at the end of - corresponding packfile. + A copy of the pack checksum at the end of the corresponding + packfile. - 20-byte SHA-1-checksum of all of the above. + Index checksum of all of the above. Pack Idx file: @@ -198,7 +204,7 @@ Pack file entry: <+ If it is not DELTA, then deflated bytes (the size above is the size before compression). If it is REF_DELTA, then - 20-byte base object name SHA-1 (the size above is the + base object name (the size above is the size of the delta data that follows). delta data, deflated. If it is OFS_DELTA, then @@ -227,9 +233,9 @@ Pack file entry: <+ - A 256-entry fan-out table just like v1. - - A table of sorted 20-byte SHA-1 object names. These are - packed together without offset values to reduce the cache - footprint of the binary search for a specific object name. + - A table of sorted object names. These are packed together + without offset values to reduce the cache footprint of the + binary search for a specific object name. - A table of 4-byte CRC32 values of the packed object data. This is new in v2 so compressed data can be copied directly @@ -248,10 +254,10 @@ Pack file entry: <+ - The same trailer as a v1 pack file: - A copy of the 20-byte SHA-1 checksum at the end of + A copy of the pack checksum at the end of corresponding packfile. - 20-byte SHA-1-checksum of all of the above. + Index checksum of all of the above. == multi-pack-index (MIDX) files have the following format: @@ -273,7 +279,12 @@ HEADER: Git only writes or recognizes version 1. 1-byte Object Id Version - Git only writes or recognizes version 1 (SHA1). + We infer the length of object IDs (OIDs) from this value: + 1 => SHA-1 + 2 => SHA-256 + If the hash type does not match the repository's hash algorithm, + the multi-pack-index file should be ignored with a warning + presented to the user. 1-byte number of "chunks" @@ -329,4 +340,4 @@ CHUNK DATA: TRAILER: - 20-byte SHA1-checksum of the above contents. + Index checksum of the above contents. diff --git a/Documentation/technical/partial-clone.txt b/Documentation/technical/partial-clone.txt index b9e17e7a28..0780d30cac 100644 --- a/Documentation/technical/partial-clone.txt +++ b/Documentation/technical/partial-clone.txt @@ -171,20 +171,13 @@ additional flag. Fetching Missing Objects ------------------------ -- Fetching of objects is done using the existing transport mechanism using - transport_fetch_refs(), setting a new transport option - TRANS_OPT_NO_DEPENDENTS to indicate that only the objects themselves are - desired, not any object that they refer to. -+ -Because some transports invoke fetch_pack() in the same process, fetch_pack() -has been updated to not use any object flags when the corresponding argument -(no_dependents) is set. +- Fetching of objects is done by invoking a "git fetch" subprocess. - The local repository sends a request with the hashes of all requested - objects as "want" lines, and does not perform any packfile negotiation. + objects, and does not perform any packfile negotiation. It then receives a packfile. -- Because we are reusing the existing fetch-pack mechanism, fetching +- Because we are reusing the existing fetch mechanism, fetching currently fetches all objects referred to by the requested objects, even though they are not necessary. diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index 36ccd14f97..124d716807 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -324,15 +324,19 @@ allow-tip-sha1-in-want ---------------------- If the upload-pack server advertises this capability, fetch-pack may -send "want" lines with SHA-1s that exist at the server but are not -advertised by upload-pack. +send "want" lines with object names that exist at the server but are not +advertised by upload-pack. For historical reasons, the name of this +capability contains "sha1". Object names are always given using the +object format negotiated through the 'object-format' capability. allow-reachable-sha1-in-want ---------------------------- If the upload-pack server advertises this capability, fetch-pack may -send "want" lines with SHA-1s that exist at the server but are not -advertised by upload-pack. +send "want" lines with object names that exist at the server but are not +advertised by upload-pack. For historical reasons, the name of this +capability contains "sha1". Object names are always given using the +object format negotiated through the 'object-format' capability. push-cert=<nonce> ----------------- diff --git a/Documentation/technical/shallow.txt b/Documentation/technical/shallow.txt index 01dedfe9ff..f3738baa0f 100644 --- a/Documentation/technical/shallow.txt +++ b/Documentation/technical/shallow.txt @@ -13,7 +13,7 @@ pretend as if they are root commits (e.g. "git log" traversal stops after showing them; "git fsck" does not complain saying the commits listed on their "parent" lines do not exist). -Each line contains exactly one SHA-1. When read, a commit_graft +Each line contains exactly one object name. When read, a commit_graft will be constructed, which has nr_parent < 0 to make it easier to discern from user provided grafts. |