Go to file

Derrick Stolee 1687150b5d hashfile: allow skipping the hash function The hashfile API is useful for generating files that include a trailing hash of the file's contents up to that point. Using such a hash is helpful for verifying the file for corruption-at-rest, such as a faulty drive causing flipped bits. Git's index file includes this trailing hash, so it uses a 'struct hashfile' to handle the I/O to the file. This was very convenient to allow using the hashfile methods during these operations. However, hashing the file contents during write comes at a performance penalty. It's slower to hash the bytes on their way to the disk than without that step. This problem is made worse by the replacement of hardware-accelerated SHA1 computations with the software-based sha1dc computation. This write cost is significant, and the checksum capability is likely not worth that cost for such a short-lived file. The index is rewritten frequently and the only time the checksum is checked is during 'git fsck'. Thus, it would be helpful to allow a user to opt-out of the hash computation. We first need to allow Git to opt-out of the hash computation in the hashfile API. The buffered writes of the API are still helpful, so it makes sense to make the change here. Introduce a new 'skip_hash' option to 'struct hashfile'. When set, the update_fn and final_fn members of the_hash_algo are skipped. When finalizing the hashfile, the trailing hash is replaced with the null hash. This use of a trailing null hash would be desireable in either case, since we do not want to special case a file format to have a different length depending on whether it was hashed or not. When the final bytes of a file are all zero, we can infer that it was written without hashing, and thus that verification is not available as a check for file consistency. This also means that we could easily toggle hashing for any file format we desire. A version of this patch has existed in the microsoft/git fork since 2017 [1] (the linked commit was rebased in 2018, but the original dates back to January 2017). Here, the change to make the index use this fast path is delayed until a later change. [1] `21fed2d914` Co-authored-by: Kevin Willford <kewillf@microsoft.com> Signed-off-by: Kevin Willford <kewillf@microsoft.com> Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>		2023-01-07 07:46:14 +09:00
.github	ci: use a newer `github-script` version	2022-12-10 16:32:16 +09:00
Documentation	Git 2.38.2	2022-12-11 09:34:51 +09:00
block-sha1	…
builtin	Merge branch 'ab/doc-synopsis-and-cmd-usage'	2022-11-29 10:41:06 +09:00
ci	Merge branch 'jx/ci-ubuntu-fix' into maint-2.38	2022-12-10 16:17:47 +09:00
compat	Merge branch 'sz/macos-fsmonitor-symlinks'	2022-11-23 11:22:25 +09:00
contrib	Merge branch 'ab/fewer-the-index-macros'	2022-12-01 18:38:07 +09:00
ewah	…
git-gui	Makefiles: change search through $(MAKEFLAGS) for GNU make 4.4	2022-12-01 07:24:12 +09:00
gitk-git	…
gitweb	…
mergetools	…
negotiator	negotiator/skipping: avoid stack overflow	2022-10-25 17:14:40 -07:00
oss-fuzz	…
perl	…
po	l10n: zh_TW.po: Git 2.39-rc2	2022-12-11 01:27:25 +08:00
refs	…
reftable	…
sha1collisiondetection@855827c583	…
sha1dc	…
sha256	…
t	rebase --update-refs: avoid unintended ref deletion	2022-12-09 19:31:45 +09:00
templates	…
trace2	…
xdiff	…
.cirrus.yml	…
.clang-format	…
.editorconfig	…
.gitattributes	…
.gitignore	Merge branch 'ab/coccicheck-incremental'	2022-11-23 11:22:23 +09:00
.gitmodules	…
.mailmap	mailmap: update email address of Matheus Tavares	2022-12-10 09:17:36 +09:00
.tsan-suppressions	…
CODE_OF_CONDUCT.md	…
COPYING	…
GIT-VERSION-GEN	Git 2.39	2022-12-12 09:59:08 +09:00
INSTALL	INSTALL: remove discussion of SHA-1 backends	2022-11-07 22:11:51 -05:00
LGPL-2.1	…
Makefile	Merge branch 'ab/coccicheck-incremental'	2022-11-23 11:22:23 +09:00
README.md	…
RelNotes	Downmerge a handful of topics for 2.38.2	2022-10-25 17:11:39 -07:00
SECURITY.md	…
abspath.c	…
aclocal.m4	…
add-interactive.c	read-cache API & users: make discard_index() return void	2022-11-21 12:06:15 +09:00
add-interactive.h	…
add-patch.c	read-cache API & users: make discard_index() return void	2022-11-21 12:06:15 +09:00
advice.c	…
advice.h	…
alias.c	…
alias.h	…
alloc.c	…
alloc.h	…
apply.c	Merge branch 'tb/cap-patch-at-1gb'	2022-10-30 21:04:43 -04:00
apply.h	…
archive-tar.c	archive-tar: report filter start error only once	2022-10-30 19:50:43 -04:00
archive-zip.c	…
archive.c	Merge branch 'rs/archive-dedup-printf' into maint-2.38	2022-10-27 15:24:14 -07:00
archive.h	…
attr.c	…
attr.h	…
banned.h	…
base85.c	…
bisect.c	replace and remove run_command_v_opt()	2022-10-30 14:04:51 -04:00
bisect.h	…
blame.c	…
blame.h	…
blob.c	…
blob.h	…
bloom.c	…
bloom.h	…
branch.c	…
branch.h	…
builtin.h	…
bulk-checkin.c	…
bulk-checkin.h	…
bundle-uri.c	…
bundle-uri.h	…
bundle.c	…
bundle.h	Merge branch 'ds/bundle-uri-3'	2022-10-30 21:04:44 -04:00
cache-tree.c	…
cache-tree.h	…
cache.h	cocci: apply "pending" index-compatibility to some "builtin/*.c"	2022-11-21 12:06:15 +09:00
cbtree.c	…
cbtree.h	…
chdir-notify.c	…
chdir-notify.h	…
check-builtins.sh	…
checkout.c	…
checkout.h	…
chunk-format.c	…
chunk-format.h	…
color.c	…
color.h	…
column.c	…
column.h	…
combine-diff.c	…
command-list.txt	…
commit-graph.c	…
commit-graph.h	…
commit-reach.c	…
commit-reach.h	…
commit-slab-decl.h	…
commit-slab-impl.h	…
commit-slab.h	…
commit.c	Merge branch 'pw/rebase-keep-base-fixes'	2022-10-30 21:04:42 -04:00
commit.h	…
common-main.c	…
config.c	Merge branch 'pw/config-int-parse-fixes'	2022-11-28 12:13:43 +09:00
config.h	…
config.mak.dev	…
config.mak.in	…
config.mak.uname	…
configure.ac	…
connect.c	…
connect.h	…
connected.c	receive-pack: only use visible refs for connectivity check	2022-11-17 16:22:52 -05:00
connected.h	receive-pack: only use visible refs for connectivity check	2022-11-17 16:22:52 -05:00
convert.c	…
convert.h	…
copy.c	…
credential.c	…
credential.h	…
csum-file.c	hashfile: allow skipping the hash function	2023-01-07 07:46:14 +09:00
csum-file.h	hashfile: allow skipping the hash function	2023-01-07 07:46:14 +09:00
ctype.c	…
daemon.c	…
date.c	…
date.h	…
decorate.c	…
decorate.h	…
delta-islands.c	delta-islands: free island-related data after use	2022-11-18 18:30:49 -05:00
delta-islands.h	…
delta.h	…
detect-compiler	…
diagnose.c	…
diagnose.h	…
diff-delta.c	…
diff-lib.c	…
diff-merges.c	…
diff-merges.h	…
diff-no-index.c	…
diff.c	Merge branch 'sg/plug-line-log-leaks'	2022-11-28 12:13:46 +09:00
diff.h	…
diffcore-break.c	…
diffcore-delta.c	…
diffcore-order.c	…
diffcore-pickaxe.c	…
diffcore-rename.c	…
diffcore-rotate.c	…
diffcore.h	line-log: free diff queue when processing non-merge commits	2022-11-02 20:16:34 -04:00
dir-iterator.c	…
dir-iterator.h	…
dir.c	Merge branch 'rs/use-fspathncmp' into maint-2.38	2022-10-27 15:24:13 -07:00
dir.h	…
editor.c	…
entry.c	…
entry.h	…
environment.c	…
environment.h	…
exec-cmd.c	…
exec-cmd.h	…
fetch-negotiator.c	…
fetch-negotiator.h	…
fetch-pack.c	…
fetch-pack.h	…
fmt-merge-msg.c	…
fmt-merge-msg.h	…
fsck.c	…
fsck.h	fsck: document msg-id	2022-10-25 15:44:18 -07:00
fsmonitor--daemon.h	…
fsmonitor-ipc.c	replace and remove run_command_v_opt_tr2()	2022-10-30 14:04:48 -04:00
fsmonitor-ipc.h	…
fsmonitor-path-utils.h	…
fsmonitor-settings.c	…
fsmonitor-settings.h	…
fsmonitor.c	…
fsmonitor.h	…
generate-cmdlist.sh	…
generate-configlist.sh	…
generate-hooklist.sh	…
gettext.c	…
gettext.h	…
git-add--interactive.perl	…
git-archimport.perl	…
git-bisect.sh	bisect--helper: parse subcommand with OPT_SUBCOMMAND	2022-11-11 17:04:57 -05:00
git-compat-util.h	Merge branch 'ab/unused-annotation' into maint-2.38	2022-10-27 15:24:12 -07:00
git-curl-compat.h	…
git-cvsexportcommit.perl	…
git-cvsimport.perl	…
git-cvsserver.perl	…
git-difftool--helper.sh	…
git-filter-branch.sh	…
git-instaweb.sh	…
git-merge-octopus.sh	…
git-merge-one-file.sh	…
git-merge-resolve.sh	…
git-mergetool--lib.sh	…
git-mergetool.sh	…
git-p4.py	…
git-quiltimport.sh	…
git-request-pull.sh	…
git-send-email.perl	…
git-sh-i18n.sh	…
git-sh-setup.sh	…
git-submodule.sh	submodule--helper: drop "update --prefix <pfx>" for "-C <pfx> update"	2022-11-08 14:55:30 -05:00
git-svn.perl	…
git-web--browse.sh	…
git.c	Merge branch 'ab/submodule-helper-prep-only'	2022-11-23 11:22:22 +09:00
git.rc	…
gpg-interface.c	Merge branch 'pw/ssh-sign-report-errors' into maint-2.38	2022-10-25 17:11:35 -07:00
gpg-interface.h	…
graph.c	…
graph.h	…
grep.c	…
grep.h	…
hash-lookup.c	…
hash-lookup.h	…
hash.h	…
hashmap.c	…
hashmap.h	…
help.c	Merge branch 'ab/doc-synopsis-and-cmd-usage'	2022-10-28 11:26:54 -07:00
help.h	…
hex.c	…
hook.c	…
hook.h	…
http-backend.c	…
http-fetch.c	…
http-push.c	…
http-walker.c	…
http.c	http: redact curl h2h3 headers in info	2022-11-14 17:42:46 -05:00
http.h	…
ident.c	…
imap-send.c	…
iterator.h	…
json-writer.c	…
json-writer.h	…
khash.h	…
kwset.c	…
kwset.h	…
levenshtein.c	…
levenshtein.h	…
line-log.c	line-log: free the diff queues' arrays when processing merge commits	2022-11-02 20:16:34 -04:00
line-log.h	…
line-range.c	…
line-range.h	…
linear-assignment.c	…
linear-assignment.h	…
list-objects-filter-options.c	…
list-objects-filter-options.h	…
list-objects-filter.c	list-objects-filter: plug combine_filter_data leak	2022-11-21 16:43:26 +09:00
list-objects-filter.h	…
list-objects.c	…
list-objects.h	…
list.h	…
ll-merge.c	Merge branch 'rs/no-more-run-command-v'	2022-11-08 17:15:12 -05:00
ll-merge.h	…
lockfile.c	…
lockfile.h	…
log-tree.c	…
log-tree.h	…
ls-refs.c	refs: get rid of global list of hidden refs	2022-11-17 16:22:51 -05:00
ls-refs.h	…
mailinfo.c	…
mailinfo.h	…
mailmap.c	…
mailmap.h	…
match-trees.c	…
mem-pool.c	…
mem-pool.h	…
merge-blobs.c	…
merge-blobs.h	…
merge-ort-wrappers.c	…
merge-ort-wrappers.h	…
merge-ort.c	Merge branch 'en/ort-dir-rename-and-symlink-fix'	2022-10-30 21:04:43 -04:00
merge-ort.h	…
merge-recursive.c	merge-recursive: fix variable typo in error message	2022-11-27 10:26:10 +09:00
merge-recursive.h	…
merge.c	use child_process members "args" and "env" directly	2022-10-30 14:04:40 -04:00
mergesort.h	…
midx.c	Merge branch 'tb/midx-bitmap-selection-fix'	2022-10-27 14:51:52 -07:00
midx.h	…
name-hash.c	…
notes-cache.c	…
notes-cache.h	…
notes-merge.c	…
notes-merge.h	…
notes-utils.c	…
notes-utils.h	…
notes.c	…
notes.h	…
object-file.c	object-file: use real paths when adding alternates	2022-11-25 09:44:08 +09:00
object-name.c	…
object-store.h	…
object.c	parse_object(): simplify blob conditional	2022-11-22 10:13:54 +09:00
object.h	…
oid-array.c	…
oid-array.h	…
oidmap.c	…
oidmap.h	…
oidset.c	…
oidset.h	…
oidtree.c	…
oidtree.h	…
pack-bitmap-write.c	…
pack-bitmap.c	…
pack-bitmap.h	…
pack-check.c	…
pack-mtimes.c	…
pack-mtimes.h	…
pack-objects.c	…
pack-objects.h	…
pack-revindex.c	…
pack-revindex.h	…
pack-write.c	…
pack.h	…
packfile.c	…
packfile.h	…
pager.c	…
parallel-checkout.c	…
parallel-checkout.h	…
parse-options-cb.c	…
parse-options.c	…
parse-options.h	…
patch-delta.c	…
patch-ids.c	Merge branch 'jz/patch-id'	2022-10-30 21:04:41 -04:00
patch-ids.h	…
path.c	adjust_shared_perm(): leave g+s alone when the group does not matter	2022-10-28 14:55:27 -07:00
path.h	…
pathspec.c	…
pathspec.h	…
pkt-line.c	…
pkt-line.h	…
preload-index.c	…
pretty.c	…
pretty.h	…
prio-queue.c	…
prio-queue.h	…
progress.c	…
progress.h	…
promisor-remote.c	…
promisor-remote.h	…
prompt.c	…
prompt.h	…
protocol-caps.c	…
protocol-caps.h	…
protocol.c	…
protocol.h	…
prune-packed.c	…
prune-packed.h	…
quote.c	…
quote.h	…
range-diff.c	…
range-diff.h	…
reachable.c	…
reachable.h	…
read-cache.c	read-cache API & users: make discard_index() return void	2022-11-21 12:06:15 +09:00
rebase-interactive.c	…
rebase-interactive.h	…
rebase.c	…
rebase.h	…
ref-filter.c	ref-filter: fix parsing of signatures with CRLF and no body	2022-11-02 21:36:04 -04:00
ref-filter.h	…
reflog-walk.c	…
reflog-walk.h	…
reflog.c	…
reflog.h	…
refs.c	refs: get rid of global list of hidden refs	2022-11-17 16:22:51 -05:00
refs.h	refs: get rid of global list of hidden refs	2022-11-17 16:22:51 -05:00
refspec.c	…
refspec.h	…
remote-curl.c	…
remote.c	…
remote.h	…
replace-object.c	…
replace-object.h	…
repo-settings.c	Merge branch 'es/mark-gc-cruft-as-experimental'	2022-11-08 17:14:48 -05:00
repository.c	{builtin/*,repository}.c: add & use "USE_THE_INDEX_VARIABLE"	2022-11-21 12:06:15 +09:00
repository.h	Merge branch 'es/mark-gc-cruft-as-experimental'	2022-11-08 17:14:48 -05:00
rerere.c	…
rerere.h	…
reset.c	rebase: use 'skip_cache_tree_update' option	2022-11-10 21:49:34 -05:00
reset.h	…
resolve-undo.c	…
resolve-undo.h	…
revision.c	Merge branch 'ps/receive-use-only-advertised'	2022-11-23 11:22:25 +09:00
revision.h	Merge branch 'ps/receive-use-only-advertised'	2022-11-23 11:22:25 +09:00
run-command.c	Merge branch 'rs/no-more-run-command-v'	2022-11-08 17:15:12 -05:00
run-command.h	Merge branch 'rs/no-more-run-command-v'	2022-11-08 17:15:12 -05:00
scalar.c	Merge branch 'js/remove-stale-scalar-repos'	2022-11-23 11:22:23 +09:00
send-pack.c	…
send-pack.h	…
sequencer.c	rebase --update-refs: avoid unintended ref deletion	2022-12-09 19:31:45 +09:00
sequencer.h	sequencer: stop exporting GIT_REFLOG_ACTION	2022-11-09 18:15:43 -05:00
serve.c	…
serve.h	…
server-info.c	…
setup.c	…
sh-i18n--envsubst.c	…
sha1dc_git.c	…
sha1dc_git.h	Makefile & test-tool: replace "DC_SHA1" variable with a "define"	2022-11-07 22:11:51 -05:00
shallow.c	…
shallow.h	…
shared.mak	Merge branch 'ab/gnumake-4.4-fix'	2022-12-01 18:38:07 +09:00
shell.c	replace and remove run_command_v_opt()	2022-10-30 14:04:51 -04:00
shortlog.h	…
sideband.c	…
sideband.h	…
sigchain.c	…
sigchain.h	…
simple-ipc.h	…
sparse-index.c	index: raise a bug if the index is materialised more than once	2022-11-04 20:28:28 -04:00
sparse-index.h	…
split-index.c	…
split-index.h	…
stable-qsort.c	…
strbuf.c	…
strbuf.h	…
streaming.c	…
streaming.h	…
string-list.c	…
string-list.h	…
strmap.c	…
strmap.h	…
strvec.c	…
strvec.h	…
sub-process.c	…
sub-process.h	…
submodule-config.c	…
submodule-config.h	…
submodule.c	Merge branch 'jt/submodule-on-demand'	2022-11-23 11:22:25 +09:00
submodule.h	submodule API & "absorbgitdirs": remove "----recursive" option	2022-11-08 14:55:30 -05:00
symlinks.c	…
tag.c	…
tag.h	…
tar.h	…
tempfile.c	…
tempfile.h	…
thread-utils.c	…
thread-utils.h	…
tmp-objdir.c	…
tmp-objdir.h	replace and remove run_command_v_opt_cd_env()	2022-10-30 14:04:47 -04:00
trace.c	…
trace.h	…
trace2.c	…
trace2.h	…
trailer.c	…
trailer.h	…
transport-helper.c	…
transport-internal.h	…
transport.c	Merge branch 'ds/bundle-uri-3'	2022-10-30 21:04:44 -04:00
transport.h	…
tree-diff.c	…
tree-walk.c	…
tree-walk.h	…
tree.c	…
tree.h	…
unicode-width.h	…
unimplemented.sh	…
unix-socket.c	…
unix-socket.h	…
unix-stream-server.c	…
unix-stream-server.h	…
unpack-trees.c	unpack-trees: add 'skip_cache_tree_update' option	2022-11-10 21:49:34 -05:00
unpack-trees.h	unpack-trees: add 'skip_cache_tree_update' option	2022-11-10 21:49:34 -05:00
upload-pack.c	refs: get rid of global list of hidden refs	2022-11-17 16:22:51 -05:00
upload-pack.h	…
url.c	…
url.h	…
urlmatch.c	…
urlmatch.h	…
usage.c	…
userdiff.c	…
userdiff.h	…
utf8.c	…
utf8.h	…
varint.c	…
varint.h	…
version.c	…
version.h	…
versioncmp.c	…
walker.c	…
walker.h	…
wildmatch.c	…
wildmatch.h	…
worktree.c	…
worktree.h	…
wrap-for-bin.sh	…
wrapper.c	…
write-or-die.c	…
ws.c	…
wt-status.c	…
wt-status.h	…
xdiff-interface.c	…
xdiff-interface.h	…
zlib.c	…

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.txt to get started, then see Documentation/giteveryday.txt for a useful minimum set of commands, and Documentation/git-<commandname>.txt 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.txt (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 with just "subscribe git" in the body to majordomo@vger.kernel.org (not the Git list). The mailing list archives are available at https://lore.kernel.org/git/, http://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