![]() In an earlier commit, a bug was described where it's possible for Git to produce non-murmur3 hashes when the platform's "char" type is signed, and there are paths with characters whose highest bit is set (i.e. all characters >= 0x80). That patch allows the caller to control which version of Bloom filters are read and written. However, even on platforms with a signed "char" type, it is possible to reuse existing Bloom filters if and only if there are no changed paths in any commit's first parent tree-diff whose characters have their highest bit set. When this is the case, we can reuse the existing filter without having to compute a new one. This is done by marking trees which are known to have (or not have) any such paths. When a commit's root tree is verified to not have any such paths, we mark it as such and declare that the commit's Bloom filter is reusable. Note that this heuristic only goes in one direction. If neither a commit nor its first parent have any paths in their trees with non-ASCII characters, then we know for certain that a path with non-ASCII characters will not appear in a tree-diff against that commit's first parent. The reverse isn't necessarily true: just because the tree-diff doesn't contain any such paths does not imply that no such paths exist in either tree. So we end up recomputing some Bloom filters that we don't strictly have to (i.e. their bits are the same no matter which version of murmur3 we use). But culling these out is impossible, since we'd have to perform the full tree-diff, which is the same effort as computing the Bloom filter from scratch. But because we can cache our results in each tree's flag bits, we can often avoid recomputing many filters, thereby reducing the time it takes to run $ git commit-graph write --changed-paths --reachable when upgrading from v1 to v2 Bloom filters. To benchmark this, let's generate a commit-graph in linux.git with v1 changed-paths in generation order[^1]: $ git clone git@github.com:torvalds/linux.git $ cd linux $ git commit-graph write --reachable --changed-paths $ graph=".git/objects/info/commit-graph" $ mv $graph{,.bak} Then let's time how long it takes to go from v1 to v2 filters (with and without the upgrade path enabled), resetting the state of the commit-graph each time: $ git config commitGraph.changedPathsVersion 2 $ hyperfine -p 'cp -f $graph.bak $graph' -L v 0,1 \ 'GIT_TEST_UPGRADE_BLOOM_FILTERS={v} git.compile commit-graph write --reachable --changed-paths' On linux.git (where there aren't any non-ASCII paths), the timings indicate that this patch represents a speed-up over recomputing all Bloom filters from scratch: Benchmark 1: GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths Time (mean ± σ): 124.873 s ± 0.316 s [User: 124.081 s, System: 0.643 s] Range (min … max): 124.621 s … 125.227 s 3 runs Benchmark 2: GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths Time (mean ± σ): 79.271 s ± 0.163 s [User: 74.611 s, System: 4.521 s] Range (min … max): 79.112 s … 79.437 s 3 runs Summary 'GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths' ran 1.58 ± 0.01 times faster than 'GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths' On git.git, we do have some non-ASCII paths, giving us a more modest improvement from 4.163 seconds to 3.348 seconds, for a 1.24x speed-up. On my machine, the stats for git.git are: - 8,285 Bloom filters computed from scratch - 10 Bloom filters generated as empty - 4 Bloom filters generated as truncated due to too many changed paths - 65,114 Bloom filters were reused when transitioning from v1 to v2. [^1]: Note that this is is important, since `--stdin-packs` or `--stdin-commits` orders commits in the commit-graph by their pack position (with `--stdin-packs`) or in the raw input (with `--stdin-commits`). Since we compute Bloom filters in the same order that commits appear in the graph, we must see a commit's (first) parent before we process the commit itself. This is only guaranteed to happen when sorting commits by their generation number. Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> |
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Documentation | ||
block-sha1 | ||
builtin | ||
ci | ||
compat | ||
contrib | ||
ewah | ||
git-gui | ||
gitk-git | ||
gitweb | ||
mergetools | ||
negotiator | ||
oss-fuzz | ||
perl | ||
po | ||
refs | ||
reftable | ||
sha1 | ||
sha1collisiondetection@855827c583 | ||
sha1dc | ||
sha256 | ||
t | ||
templates | ||
trace2 | ||
xdiff | ||
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.gitmodules | ||
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CODE_OF_CONDUCT.md | ||
COPYING | ||
GIT-VERSION-GEN | ||
INSTALL | ||
LGPL-2.1 | ||
Makefile | ||
README.md | ||
RelNotes | ||
SECURITY.md | ||
abspath.c | ||
abspath.h | ||
aclocal.m4 | ||
add-interactive.c | ||
add-interactive.h | ||
add-patch.c | ||
advice.c | ||
advice.h | ||
alias.c | ||
alias.h | ||
alloc.c | ||
alloc.h | ||
apply.c | ||
apply.h | ||
archive-tar.c | ||
archive-zip.c | ||
archive.c | ||
archive.h | ||
attr.c | ||
attr.h | ||
banned.h | ||
base85.c | ||
base85.h | ||
bisect.c | ||
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 | ||
cache-tree.c | ||
cache-tree.h | ||
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 | ||
commit.h | ||
common-main.c | ||
config.c | ||
config.h | ||
config.mak.dev | ||
config.mak.in | ||
config.mak.uname | ||
configure.ac | ||
connect.c | ||
connect.h | ||
connected.c | ||
connected.h | ||
convert.c | ||
convert.h | ||
copy.c | ||
copy.h | ||
credential.c | ||
credential.h | ||
csum-file.c | ||
csum-file.h | ||
ctype.c | ||
daemon.c | ||
date.c | ||
date.h | ||
decorate.c | ||
decorate.h | ||
delta-islands.c | ||
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 | ||
diff.h | ||
diffcore-break.c | ||
diffcore-delta.c | ||
diffcore-order.c | ||
diffcore-pickaxe.c | ||
diffcore-rename.c | ||
diffcore-rotate.c | ||
diffcore.h | ||
dir-iterator.c | ||
dir-iterator.h | ||
dir.c | ||
dir.h | ||
editor.c | ||
editor.h | ||
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 | ||
fsmonitor--daemon.h | ||
fsmonitor-ipc.c | ||
fsmonitor-ipc.h | ||
fsmonitor-ll.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-archimport.perl | ||
git-compat-util.h | ||
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 | ||
git-svn.perl | ||
git-web--browse.sh | ||
git-zlib.c | ||
git-zlib.h | ||
git.c | ||
git.rc | ||
gpg-interface.c | ||
gpg-interface.h | ||
graph.c | ||
graph.h | ||
grep.c | ||
grep.h | ||
hash-ll.h | ||
hash-lookup.c | ||
hash-lookup.h | ||
hash.h | ||
hashmap.c | ||
hashmap.h | ||
help.c | ||
help.h | ||
hex-ll.c | ||
hex-ll.h | ||
hex.c | ||
hex.h | ||
hook.c | ||
hook.h | ||
http-backend.c | ||
http-fetch.c | ||
http-push.c | ||
http-walker.c | ||
http.c | ||
http.h | ||
ident.c | ||
ident.h | ||
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.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.h | ||
list-objects.c | ||
list-objects.h | ||
list.h | ||
lockfile.c | ||
lockfile.h | ||
log-tree.c | ||
log-tree.h | ||
ls-refs.c | ||
ls-refs.h | ||
mailinfo.c | ||
mailinfo.h | ||
mailmap.c | ||
mailmap.h | ||
match-trees.c | ||
match-trees.h | ||
mem-pool.c | ||
mem-pool.h | ||
merge-blobs.c | ||
merge-blobs.h | ||
merge-ll.c | ||
merge-ll.h | ||
merge-ort-wrappers.c | ||
merge-ort-wrappers.h | ||
merge-ort.c | ||
merge-ort.h | ||
merge-recursive.c | ||
merge-recursive.h | ||
merge.c | ||
merge.h | ||
mergesort.h | ||
midx.c | ||
midx.h | ||
name-hash.c | ||
name-hash.h | ||
neue | ||
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.h | ||
object-name.c | ||
object-name.h | ||
object-store-ll.h | ||
object-store.h | ||
object.c | ||
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 | ||
pager.h | ||
parallel-checkout.c | ||
parallel-checkout.h | ||
parse-options-cb.c | ||
parse-options.c | ||
parse-options.h | ||
parse.c | ||
parse.h | ||
patch-delta.c | ||
patch-ids.c | ||
patch-ids.h | ||
path.c | ||
path.h | ||
pathspec.c | ||
pathspec.h | ||
pkt-line.c | ||
pkt-line.h | ||
preload-index.c | ||
preload-index.h | ||
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-ll.h | ||
read-cache.c | ||
read-cache.h | ||
rebase-interactive.c | ||
rebase-interactive.h | ||
rebase.c | ||
rebase.h | ||
ref-filter.c | ||
ref-filter.h | ||
reflog-walk.c | ||
reflog-walk.h | ||
reflog.c | ||
reflog.h | ||
refs.c | ||
refs.h | ||
refspec.c | ||
refspec.h | ||
remote-curl.c | ||
remote.c | ||
remote.h | ||
replace-object.c | ||
replace-object.h | ||
repo-settings.c | ||
repository.c | ||
repository.h | ||
rerere.c | ||
rerere.h | ||
reset.c | ||
reset.h | ||
resolve-undo.c | ||
resolve-undo.h | ||
revision.c | ||
revision.h | ||
run-command.c | ||
run-command.h | ||
sane-ctype.h | ||
scalar.c | ||
send-pack.c | ||
send-pack.h | ||
sequencer.c | ||
sequencer.h | ||
serve.c | ||
serve.h | ||
server-info.c | ||
server-info.h | ||
setup.c | ||
setup.h | ||
sh-i18n--envsubst.c | ||
sha1dc_git.c | ||
sha1dc_git.h | ||
shallow.c | ||
shallow.h | ||
shared.mak | ||
shell.c | ||
shortlog.h | ||
sideband.c | ||
sideband.h | ||
sigchain.c | ||
sigchain.h | ||
simple-ipc.h | ||
sparse-index.c | ||
sparse-index.h | ||
split-index.c | ||
split-index.h | ||
stable-qsort.c | ||
statinfo.c | ||
statinfo.h | ||
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 | ||
submodule.h | ||
symlinks.c | ||
symlinks.h | ||
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tar.h | ||
tempfile.c | ||
tempfile.h | ||
thread-utils.c | ||
thread-utils.h | ||
tmp-objdir.c | ||
tmp-objdir.h | ||
trace.c | ||
trace.h | ||
trace2.c | ||
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trailer.c | ||
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transport-helper.c | ||
transport-internal.h | ||
transport.c | ||
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 | ||
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unpack-trees.c | ||
unpack-trees.h | ||
upload-pack.c | ||
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 | ||
versioncmp.h | ||
walker.c | ||
walker.h | ||
wildmatch.c | ||
wildmatch.h | ||
worktree.c | ||
worktree.h | ||
wrap-for-bin.sh | ||
wrapper.c | ||
wrapper.h | ||
write-or-die.c | ||
write-or-die.h | ||
ws.c | ||
ws.h | ||
wt-status.c | ||
wt-status.h | ||
xdiff-interface.c | ||
xdiff-interface.h |
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/, 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