diff options
Diffstat (limited to 'Documentation/technical')
| -rw-r--r-- | Documentation/technical/api-parse-options.txt | 5 | ||||
| -rw-r--r-- | Documentation/technical/api-trace2.txt | 58 | ||||
| -rw-r--r-- | Documentation/technical/bitmap-format.txt | 71 | ||||
| -rw-r--r-- | Documentation/technical/directory-rename-detection.txt | 14 | ||||
| -rw-r--r-- | Documentation/technical/http-protocol.txt | 3 | ||||
| -rw-r--r-- | Documentation/technical/multi-pack-index.txt | 32 | ||||
| -rw-r--r-- | Documentation/technical/pack-format.txt | 13 | ||||
| -rw-r--r-- | Documentation/technical/protocol-v2.txt | 23 | ||||
| -rw-r--r-- | Documentation/technical/rerere.txt | 10 | ||||
| -rw-r--r-- | Documentation/technical/signature-format.txt | 24 |
10 files changed, 187 insertions, 66 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/api-trace2.txt b/Documentation/technical/api-trace2.txt index 037a91cbca..bb13ca3db8 100644 --- a/Documentation/technical/api-trace2.txt +++ b/Documentation/technical/api-trace2.txt @@ -128,7 +128,7 @@ yields ------------ $ cat ~/log.event -{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"2","exe":"2.20.1.155.g426c96fcdb"} +{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"3","exe":"2.20.1.155.g426c96fcdb"} {"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]} {"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"} {"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0} @@ -391,7 +391,7 @@ only present on the "start" and "atexit" events. { "event":"version", ... - "evt":"2", # EVENT format version + "evt":"3", # EVENT format version "exe":"2.20.1.155.g426c96fcdb" # git version } ------------ @@ -493,6 +493,20 @@ about specific error arguments. } ------------ +`"cmd_ancestry"`:: + This event contains the text command name for the parent (and earlier + generations of parents) of the current process, in an array ordered from + nearest parent to furthest great-grandparent. It may not be implemented + on all platforms. ++ +------------ +{ + "event":"cmd_ancestry", + ... + "ancestry":["bash","tmux: server","systemd"] +} +------------ + `"cmd_name"`:: This event contains the command name for this git process and the hierarchy of commands from parent git processes. @@ -599,6 +613,46 @@ stopping after the waitpid() and includes OS process creation overhead). So this time will be slightly larger than the atexit time reported by the child process itself. +`"child_ready"`:: + This event is generated after the current process has started + a background process and released all handles to it. ++ +------------ +{ + "event":"child_ready", + ... + "child_id":2, + "pid":14708, # child PID + "ready":"ready", # child ready state + "t_rel":0.110605 # observed run-time of child process +} +------------ ++ +Note that the session-id of the child process is not available to +the current/spawning process, so the child's PID is reported here as +a hint for post-processing. (But it is only a hint because the child +process may be a shell script which doesn't have a session-id.) ++ +This event is generated after the child is started in the background +and given a little time to boot up and start working. If the child +startups normally and while the parent is still waiting, the "ready" +field will have the value "ready". +If the child is too slow to start and the parent times out, the field +will have the value "timeout". +If the child starts but the parent is unable to probe it, the field +will have the value "error". ++ +After the parent process emits this event, it will release all of its +handles to the child process and treat the child as a background +daemon. So even if the child does eventually finish booting up, +the parent will not emit an updated event. ++ +Note that the `t_rel` field contains the observed run time in seconds +when the parent released the child process into the background. +The child is assumed to be a long-running daemon process and may +outlive the parent process. So the parent's child event times should +not be compared to the child's atexit times. + `"exec"`:: This event is generated before git attempts to `exec()` another command rather than starting a child process. 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/directory-rename-detection.txt b/Documentation/technical/directory-rename-detection.txt index 49b83ef3cc..029ee2cedc 100644 --- a/Documentation/technical/directory-rename-detection.txt +++ b/Documentation/technical/directory-rename-detection.txt @@ -2,9 +2,9 @@ Directory rename detection ========================== Rename detection logic in diffcore-rename that checks for renames of -individual files is aggregated and analyzed in merge-recursive for cases -where combinations of renames indicate that a full directory has been -renamed. +individual files is also aggregated there and then analyzed in either +merge-ort or merge-recursive for cases where combinations of renames +indicate that a full directory has been renamed. Scope of abilities ------------------ @@ -88,9 +88,11 @@ directory rename detection support in: Folks have requested in the past that `git diff` detect directory renames and somehow simplify its output. It is not clear whether this would be desirable or how the output should be simplified, so this was - simply not implemented. Further, to implement this, directory rename - detection logic would need to move from merge-recursive to - diffcore-rename. + simply not implemented. Also, while diffcore-rename has most of the + logic for detecting directory renames, some of the logic is still found + within merge-ort and merge-recursive. Fully supporting directory + rename detection in diffs would require copying or moving the remaining + bits of logic to the diff machinery. * am 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..f2221d2b44 100644 --- a/Documentation/technical/multi-pack-index.txt +++ b/Documentation/technical/multi-pack-index.txt @@ -17,13 +17,14 @@ is not feasible due to storage space or excessive repack times. The multi-pack-index (MIDX for short) stores a list of objects and their offsets into multiple packfiles. It contains: -- A list of packfile names. -- A sorted list of object IDs. -- A list of metadata for the ith object ID including: - - A value j referring to the jth packfile. - - An offset within the jth packfile for the object. -- If large offsets are required, we use another list of large +* A list of packfile names. +* A sorted list of object IDs. +* A list of metadata for the ith object ID including: +** A value j referring to the jth packfile. +** An offset within the jth packfile for the object. +* If large offsets are required, we use another list of large offsets similar to version 2 pack-indexes. +- An optional list of objects in pseudo-pack order (used with MIDX bitmaps). Thus, we can provide O(log N) lookup time for any number of packfiles. @@ -36,7 +37,9 @@ Design Details directory of an alternate. It refers only to packfiles in that same directory. -- The core.multiPackIndex config setting must be on to consume MIDX files. +- The core.multiPackIndex config setting must be on (which is the + default) to consume MIDX files. Setting it to `false` prevents + Git from reading a MIDX file, even if one exists. - The file format includes parameters for the object ID hash function, so a future change of hash algorithm does not require @@ -71,14 +74,10 @@ 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". @@ -89,11 +88,6 @@ Future Work helpful to organize packfiles by object type (commit, tree, blob, etc.) and use this metadata to help that maintenance. -- The partial clone feature records special "promisor" packs that - may point to objects that are not stored locally, but available - on request to a server. The multi-pack-index does not currently - track these promisor packs. - Related Links ------------- [0] https://bugs.chromium.org/p/git/issues/detail?id=6 diff --git a/Documentation/technical/pack-format.txt b/Documentation/technical/pack-format.txt index 8d2f42f29e..6d3efb7d16 100644 --- a/Documentation/technical/pack-format.txt +++ b/Documentation/technical/pack-format.txt @@ -376,6 +376,11 @@ CHUNK DATA: [Optional] Object Large Offsets (ID: {'L', 'O', 'F', 'F'}) 8-byte offsets into large packfiles. + [Optional] Bitmap pack order (ID: {'R', 'I', 'D', 'X'}) + A list of MIDX positions (one per object in the MIDX, num_objects in + total, each a 4-byte unsigned integer in network byte order), sorted + according to their relative bitmap/pseudo-pack positions. + TRAILER: Index checksum of the above contents. @@ -456,9 +461,5 @@ In short, a MIDX's pseudo-pack is the de-duplicated concatenation of objects in packs stored by the MIDX, laid out in pack order, and the packs arranged in MIDX order (with the preferred pack coming first). -Finally, note that the MIDX's reverse index is not stored as a chunk in -the multi-pack-index itself. This is done because the reverse index -includes the checksum of the pack or MIDX to which it belongs, which -makes it impossible to write in the MIDX. To avoid races when rewriting -the MIDX, a MIDX reverse index includes the MIDX's checksum in its -filename (e.g., `multi-pack-index-xyz.rev`). +The MIDX's reverse index is stored in the optional 'RIDX' chunk within +the MIDX itself. diff --git a/Documentation/technical/protocol-v2.txt b/Documentation/technical/protocol-v2.txt index 1040d85319..8a877d27e2 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 ------------------------ @@ -116,11 +125,11 @@ command can be requested at a time. empty-request = flush-pkt command-request = command capability-list - [command-args] + delim-pkt + command-args flush-pkt command = PKT-LINE("command=" key LF) - command-args = delim-pkt - *command-specific-arg + command-args = *command-specific-arg command-specific-args are packet line framed arguments defined by each individual command. @@ -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. diff --git a/Documentation/technical/rerere.txt b/Documentation/technical/rerere.txt index af5f9fc24f..35d4541433 100644 --- a/Documentation/technical/rerere.txt +++ b/Documentation/technical/rerere.txt @@ -14,9 +14,9 @@ conflicts before writing them to the rerere database. Different conflict styles and branch names are normalized by stripping the labels from the conflict markers, and removing the common ancestor -version from the `diff3` conflict style. Branches that are merged -in different order are normalized by sorting the conflict hunks. More -on each of those steps in the following sections. +version from the `diff3` or `zdiff3` conflict styles. Branches that +are merged in different order are normalized by sorting the conflict +hunks. More on each of those steps in the following sections. Once these two normalization operations are applied, a conflict ID is calculated based on the normalized conflict, which is later used by @@ -42,8 +42,8 @@ get a conflict like the following: >>>>>>> AC Doing the analogous with AC2 (forking a branch ABAC2 off of branch AB -and then merging branch AC2 into it), using the diff3 conflict style, -we get a conflict like the following: +and then merging branch AC2 into it), using the diff3 or zdiff3 +conflict style, we get a conflict like the following: <<<<<<< HEAD B diff --git a/Documentation/technical/signature-format.txt b/Documentation/technical/signature-format.txt index 2c9406a56a..166721be6f 100644 --- a/Documentation/technical/signature-format.txt +++ b/Documentation/technical/signature-format.txt @@ -13,6 +13,22 @@ Signatures always begin with `-----BEGIN PGP SIGNATURE-----` and end with `-----END PGP SIGNATURE-----`, unless gpg is told to produce RFC1991 signatures which use `MESSAGE` instead of `SIGNATURE`. +Signatures sometimes appear as a part of the normal payload +(e.g. a signed tag has the signature block appended after the payload +that the signature applies to), and sometimes appear in the value of +an object header (e.g. a merge commit that merged a signed tag would +have the entire tag contents on its "mergetag" header). In the case +of the latter, the usual multi-line formatting rule for object +headers applies. I.e. the second and subsequent lines are prefixed +with a SP to signal that the line is continued from the previous +line. + +This is even true for an originally empty line. In the following +examples, the end of line that ends with a whitespace letter is +highlighted with a `$` sign; if you are trying to recreate these +example by hand, do not cut and paste them---they are there +primarily to highlight extra whitespace at the end of some lines. + The signed payload and the way the signature is embedded depends on the type of the object resp. transaction. @@ -78,7 +94,7 @@ author A U Thor <author@example.com> 1465981137 +0000 committer C O Mitter <committer@example.com> 1465981137 +0000 gpgsig -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 - + $ iQEcBAABAgAGBQJXYRjRAAoJEGEJLoW3InGJ3IwIAIY4SA6GxY3BjL60YyvsJPh/ HRCJwH+w7wt3Yc/9/bW2F+gF72kdHOOs2jfv+OZhq0q4OAN6fvVSczISY/82LpS7 DVdMQj2/YcHDT4xrDNBnXnviDO9G7am/9OE77kEbXrp7QPxvhjkicHNwy2rEflAA @@ -128,13 +144,13 @@ mergetag object 04b871796dc0420f8e7561a895b52484b701d51a type commit tag signedtag tagger C O Mitter <committer@example.com> 1465981006 +0000 - + $ signed tag - + $ signed tag message body -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 - + $ iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh 8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods |