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Taylor Blau 177c0d6e63 midx: infer preferred pack when not given one In `9218c6a40c` (midx: allow marking a pack as preferred, 2021-03-30), the multi-pack index code learned how to select a pack which all duplicate objects are selected from. That is, if an object appears in multiple packs, select the copy in the preferred pack before breaking ties according to the other rules like pack mtime and readdir() order. Not specifying a preferred pack can cause serious problems with multi-pack reachability bitmaps, because these bitmaps rely on having at least one pack from which all duplicates are selected. Not having such a pack causes problems with the code in pack-objects to reuse packs verbatim (e.g., that code assumes that a delta object in a chunk of pack sent verbatim will have its base object sent from the same pack). So why does not marking a pack preferred cause problems here? The reason is roughly as follows: - Ties are broken (when handling duplicate objects) by sorting according to midx_oid_compare(), which sorts objects by OID, preferred-ness, pack mtime, and finally pack ID (more on that later). - The psuedo pack-order (described in Documentation/technical/pack-format.txt under the section "multi-pack-index reverse indexes") is computed by midx_pack_order(), and sorts by pack ID and pack offset, with preferred packs sorting first. - But! Pack IDs come from incrementing the pack count in add_pack_to_midx(), which is a callback to for_each_file_in_pack_dir(), meaning that pack IDs are assigned in readdir() order. When specifying a preferred pack, all of that works fine, because duplicate objects are correctly resolved in favor of the copy in the preferred pack, and the preferred pack sorts first in the object order. "Sorting first" is critical, because the bitmap code relies on finding out which pack holds the first object in the MIDX's pseudo pack-order to determine which pack is preferred. But if we didn't specify a preferred pack, and the pack which comes first in readdir() order does not also have the lowest timestamp, then it's possible that that pack (the one that sorts first in pseudo-pack order, which the bitmap code will treat as the preferred one) did not have all duplicate objects resolved in its favor, resulting in breakage. The fix is simple: pick a (semi-arbitrary, non-empty) preferred pack when none was specified. This forces that pack to have duplicates resolved in its favor, and (critically) to sort first in pseudo-pack order. Unfortunately, testing this behavior portably isn't possible, since it depends on readdir() order which isn't guaranteed by POSIX. (Note that multi-pack reachability bitmaps have yet to be implemented; so in that sense this patch is fixing a bug which does not yet exist. But by having this patch beforehand, we can prevent the bug from ever materializing.) Signed-off-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>		2021-09-01 10:58:43 -07:00
.github	…
Documentation	midx: reject empty `--preferred-pack`'s	2021-09-01 10:58:43 -07:00
block-sha1	…
builtin	pack-bitmap-write.c: gracefully fail to write non-closed bitmaps	2021-08-24 13:21:13 -07:00
ci	…
compat	mingw: align symlinks-related rmdir() behavior with Linux	2021-08-02 15:10:58 -07:00
contrib	…
ewah	…
git-gui	…
gitk-git	…
gitweb	…
mergetools	…
negotiator	…
perl	…
po	l10n: sv.po: Update Swedish translation (5230t0f0u)	2021-08-16 06:54:20 +08:00
ppc	…
refs	…
sha1collisiondetection@855827c583	…
sha1dc	…
sha256	…
t	midx: reject empty `--preferred-pack`'s	2021-09-01 10:58:43 -07:00
templates	…
trace2	…
xdiff	…
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CODE_OF_CONDUCT.md	…
COPYING	…
GIT-VERSION-GEN	Git 2.33	2021-08-16 12:15:44 -07:00
INSTALL	…
LGPL-2.1	…
Makefile	Merge branch 'ab/getcwd-test'	2021-08-04 13:28:55 -07:00
README.md	…
RelNotes	…
SECURITY.md	…
abspath.c	…
aclocal.m4	…
add-interactive.c	…
add-interactive.h	…
add-patch.c	…
advice.c	…
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alias.c	…
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builtin.h	…
bulk-checkin.c	…
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bundle.c	…
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cache-tree.c	Merge branch 'ds/commit-and-checkout-with-sparse-index'	2021-08-04 13:28:53 -07:00
cache-tree.h	…
cache.h	Merge branch 'jt/bulk-prefetch'	2021-08-02 14:06:42 -07:00
cbtree.c	…
cbtree.h	oidtree: avoid unaligned access to crit-bit tree	2021-08-15 13:13:50 -07:00
chdir-notify.c	…
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check-builtins.sh	…
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chunk-format.c	…
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color.c	…
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column.c	…
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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	…
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commit.c	…
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config.c	…
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date.c	…
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delta-islands.c	…
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delta.h	…
detect-compiler	…
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diff-lib.c	…
diff-merges.c	Revert 'diff-merges: let "-m" imply "-p"'	2021-08-09 13:52:01 -07:00
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diff-no-index.c	…
diff.c	Merge branch 'ab/pickaxe-pcre2'	2021-08-06 12:52:15 -07:00
diff.h	…
diffcore-break.c	…
diffcore-delta.c	…
diffcore-order.c	…
diffcore-pickaxe.c	…
diffcore-rename.c	Merge branch 'ah/plugleaks'	2021-08-04 13:28:52 -07:00
diffcore-rotate.c	…
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dir-iterator.c	…
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editor.c	…
entry.c	…
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environment.c	…
environment.h	…
exec-cmd.c	…
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fetch-negotiator.c	…
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fetch-pack.c	…
fetch-pack.h	…
fmt-merge-msg.c	…
fmt-merge-msg.h	…
fsck.c	…
fsck.h	…
fsmonitor.c	…
fsmonitor.h	…
fuzz-commit-graph.c	…
fuzz-pack-headers.c	…
fuzz-pack-idx.c	…
generate-cmdlist.sh	…
generate-configlist.sh	…
gettext.c	…
gettext.h	…
git-add--interactive.perl	…
git-archimport.perl	…
git-bisect.sh	…
git-compat-util.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-rebase--preserve-merges.sh	…
git-request-pull.sh	…
git-send-email.perl	…
git-sh-i18n.sh	…
git-sh-setup.sh	…
git-submodule.sh	Merge branch 'ar/submodule-add'	2021-08-04 13:28:52 -07:00
git-svn.perl	…
git-web--browse.sh	…
git.c	midx: disallow running outside of a repository	2021-09-01 10:58:43 -07:00
git.rc	…
gpg-interface.c	…
gpg-interface.h	…
graph.c	…
graph.h	…
grep.c	…
grep.h	…
hash-lookup.c	…
hash-lookup.h	…
hash.h	oidtree: avoid unaligned access to crit-bit tree	2021-08-15 13:13:50 -07:00
hashmap.c	…
hashmap.h	…
help.c	…
help.h	…
hex.c	…
http-backend.c	…
http-fetch.c	…
http-push.c	…
http-walker.c	…
http.c	…
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.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	…
ll-merge.c	…
ll-merge.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	…
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-perf-batch-14'	2021-08-04 13:28:54 -07:00
merge-ort.h	…
merge-recursive.c	…
merge-recursive.h	…
merge.c	…
mergesort.c	…
mergesort.h	…
midx.c	midx: infer preferred pack when not given one	2021-09-01 10:58:43 -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	Merge branch 'cb/many-alternate-optim-fixup'	2021-08-11 12:36:17 -07:00
object-name.c	…
object-store.h	object-store: avoid extra ';' from KHASH_INIT	2021-08-09 09:01:30 -07:00
object.c	…
object.h	…
oid-array.c	…
oid-array.h	…
oidmap.c	…
oidmap.h	…
oidset.c	…
oidset.h	…
oidtree.c	oidtree: avoid unaligned access to crit-bit tree	2021-08-15 13:13:50 -07:00
oidtree.h	…
pack-bitmap-write.c	pack-bitmap-write.c: free existing bitmaps	2021-08-24 13:21:13 -07:00
pack-bitmap.c	pack-bitmap.c: harden 'test_bitmap_walk()' to check type bitmaps	2021-08-24 13:21:13 -07:00
pack-bitmap.h	pack-bitmap-write.c: gracefully fail to write non-closed bitmaps	2021-08-24 13:21:13 -07:00
pack-check.c	…
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	…
patch-ids.h	…
path.c	…
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	Merge branch 'ah/plugleaks'	2021-08-04 13:28:52 -07:00
rebase-interactive.c	…
rebase-interactive.h	…
rebase.c	…
rebase.h	…
ref-filter.c	Merge branch 'ah/plugleaks'	2021-08-04 13:28:52 -07:00
ref-filter.h	…
reflog-walk.c	…
reflog-walk.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	…
send-pack.c	…
send-pack.h	…
sequencer.c	…
sequencer.h	…
serve.c	…
serve.h	…
server-info.c	…
setup.c	…
sh-i18n--envsubst.c	…
sha1dc_git.c	…
sha1dc_git.h	…
shallow.c	…
shallow.h	…
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	…
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	…
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submodule.c	…
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symlinks.c	…
tag.c	…
tag.h	…
tar.h	…
tempfile.c	…
tempfile.h	…
thread-utils.c	…
thread-utils.h	…
tmp-objdir.c	…
tmp-objdir.h	…
trace.c	…
trace.h	…
trace2.c	…
trace2.h	…
trailer.c	…
trailer.h	…
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	…
unix-stream-server.h	…
unpack-trees.c	Merge branch 'ds/commit-and-checkout-with-sparse-index'	2021-08-04 13:28:53 -07:00
unpack-trees.h	…
upload-pack.c	…
upload-pack.h	…
url.c	…
url.h	…
urlmatch.c	…
urlmatch.h	…
usage.c	…
userdiff.c	…
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utf8.c	…
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varint.c	…
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version.c	…
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versioncmp.c	…
walker.c	…
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wildmatch.c	…
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worktree.c	…
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wrapper.c	…
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ws.c	…
wt-status.c	…
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xdiff-interface.c	…
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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). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. 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