91c8989d4e
The provider chain so far holds the diff-hunks store in front of the terminal builtin computation. Open it to external processes: a pair on a path whose driver configures diff.<driver>.process is answered by a long-running process speaking a pkt-line protocol (following the filter process protocol), registered at the head of the chain and consulted before the store and before any blob is loaded. The protocol starts with the smallest request that can carry an answer: object names alone. A request is the pathname and the pair's old-oid/new-oid, with no content. The process answers with hunk lines, with a zero-hunk success that asserts the blobs equivalent (trailing newlines included), or with status=need-content, on which the pair falls through to the builtin answer. This serves the two shapes that need no content pushed to them: a cache keyed on the blob pair, and a process that fetches the blobs itself (for example over "git cat-file --batch"). A pair whose side is not a stored blob carries a NULL id; the provider sends no request and passes it. Because Git holds no content for the exchange, the answer is used as sent: hunks are validated for order, overlap, lockstep alignment, and magnitude, then replayed without the normalization xdiff applies to diffs it computes itself. The magnitude bound is the blobs' sizes, read from the object database without loading content: a blob of N bytes holds at most N lines. Because the process's answer is authoritative, it outranks the store, and its head-of-chain position says so. A pair the process answers never reaches the store and is never recorded, so nothing it produces enters the store, which holds the builtin answer only. A request it does not answer, whether need-content, a missing capability, or a missing id, passes down the chain to the builtin answer, which is what the store serves, so the store may serve such a pair and a warming run may record it. Entries recorded before a process was configured are not purged; a pair the process answers ignores them, and "git diff-hunks clear" discards them. The provider gates itself per request. The driver is looked up by the old-side path, so a renamed file resolves to the same driver, and by the repository-relative path, so a diff.relative run from a subdirectory names the pair the same way. Options the process is never told about select no process: the whitespace-ignoring options, -I, --anchored, and an algorithm forced by option or configuration (blame routes its algorithm through xdl_opts, so --histogram is covered). The request gains its last field, the path; the consumers change only by filling it, and neither names the process. The provider's state is its repository's pool of running processes, keyed by the configured command, so drivers sharing a command share a process, a submodule speaks to its own, and releasing the provider (from repo_clear()) stops them. The pool owns a copy of each command string, so an entry outlives a config re-read. A command that fails stays as an entry that is not retried: its request and every later one pass, so the store may serve the path for the rest of the command. A protocol error in a response never kills the command. The response is read through a packet reader gentle about framing, so an error takes one path: a single warning, the process stopped and marked failed, and the builtin diff for the rest of the command. That covers garbage bytes, a truncated response, an empty packet, a bare status, and an unrecognized status. Semantically invalid coordinates cost only their pair: the response is drained, the pair is computed, and the process stays alive. A path the protocol cannot carry (an embedded newline, or one too long for a packet) falls back per path rather than costing the command its process. The handshake keeps one fatal check: a process that announces a capability Git did not request aborts the command, as the long-running filter protocol does. Consulting is allowed per command, following the allow_textconv precedent. "git diff", "git log" and "git show", and "git blame" set allow_diff_process; the plumbing diff commands and the interactive-patch machinery never set it, so scripted and staging output stays builtin. The options adjust the flag: - --no-ext-diff clears it and --ext-diff sets it; - --diff-process and --no-diff-process set and clear it alone, leaving external diff drivers as they were; - format-patch clears it unconditionally, so a generated patch applies for recipients without the process; - range-diff passes --no-ext-diff to the "git log" it compares. git blame and the summary formats consult the process. For blame, a pair reported equivalent emits no hunks, so the whole commit passes to its parent. In the stat formats such a pair sums to a zero-count entry, which the "nothing changed" rule omits, as under -w. The subprocess is long-running: one startup cost across a traversal, one round-trip per consulted pair. Answers travel in struct xdl_hunk, new in xdiff-interface.h, holding xdiff's 1-based coordinates; nothing feeds them back to xdiff, since only coordinate consumers consult. A content-carrying request is the natural extension: it would serve sides that are not stored blobs and processes that want content pushed to them, and bring patch output and log -L's range tracking to the same answer. As it stands, a process's answers show in blame and the summary formats while patch output stays builtin. t4080 exercises the protocol, the per-command gate, and the error paths: - each adversarial response shape warns and falls back to builtin, the request log proving which failures disable the process and which keep it alive (a malformed hunk line, coordinates past the blob size, a count overflowing strtol(), overlapping or misaligned hunks, an unrecognized status, a bare status, an empty packet, a mid-response crash, and raw garbage); - a capability-less process and status=abort degrade without noise, and a failed start warns once and returns the path to the store; - a trailing token on a hunk line is ignored, pinning field appendability; - positive consults for git diff, git show, and diff-tree under --ext-diff and --diff-process; textconv output and gitlink sides are never identified; a diff.relative run consults by the repo-relative path; - the equivalence answer is pinned from both consumers, and a warming run past a deferring process records the pair for a later read. Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Michael Montalbo <mmontalbo@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
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| Documentation | ||
| bin-wrappers | ||
| block-sha1 | ||
| builtin | ||
| ci | ||
| compat | ||
| compiler-tricks | ||
| contrib | ||
| ewah | ||
| git-gui | ||
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| gitweb | ||
| mergetools | ||
| negotiator | ||
| odb | ||
| oss-fuzz | ||
| perl | ||
| po | ||
| refs | ||
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| sha1 | ||
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| t | ||
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| tools | ||
| trace2 | ||
| xdiff | ||
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| INSTALL | ||
| LGPL-2.1 | ||
| Makefile | ||
| README.md | ||
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| abspath.c | ||
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| command-list.txt | ||
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| list.h | ||
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| match-trees.c | ||
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| mem-pool.c | ||
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| merge-blobs.c | ||
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| meson.build | ||
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| object-file.c | ||
| object-file.h | ||
| object-name.c | ||
| object-name.h | ||
| object.c | ||
| object.h | ||
| odb.c | ||
| odb.h | ||
| oid-array.c | ||
| oid-array.h | ||
| oidmap.c | ||
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| oidset.c | ||
| oidset.h | ||
| oidtree.c | ||
| oidtree.h | ||
| pack-bitmap-write.c | ||
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| pack-bitmap.h | ||
| pack-check.c | ||
| pack-mtimes.c | ||
| pack-mtimes.h | ||
| pack-objects.c | ||
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| pack.h | ||
| packfile-list.c | ||
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| parse-options-cb.c | ||
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| parse.c | ||
| parse.h | ||
| patch-delta.c | ||
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| prune-packed.c | ||
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| refs.c | ||
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README.md
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
Issues which are security relevant should be disclosed privately to the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks