Git with broken hash generation to generate collisions between object IDs. Don't use this!
https://undefinedbehavior.de/posts/commit-vandalism/
c5c39f4e34
When a test script run with 'dash' and '--verbose-log -x' is
interrupted by ctrl-C, SIGTERM, or closing the terminal window, then
most of the time the registered EXIT trap actions are not executed.
This is an annoying issue with tests involving daemons, because they
should run cleanup commands to kill those daemon processes in the trap
on EXIT, but since these cleanup commands are not executed, the
daemons are left alive and keep their port open, thus interfering with
subsequent execution of the same test script.
The cause of this issue is the subtle combination of several factors
(bear with me, or skip over the indented part):
- Even when the test script is interrupted, the cleanup commands are
not run in the trap on INT, TERM, or HUP, but in the trap on EXIT
after the trap on the signals invokes 'exit' [1].
- According to POSIX [2]:
"The environment in which the shell executes a trap on EXIT
shall be identical to the environment immediately after the last
command executed before the trap on EXIT was taken."
Pertinent to the issue at hand is that all open file descriptors
and the state of '-x' tracing should be preserved. All shells
I've tried [3] preserve '-x'. Unfortunately, however:
- 'dash' doesn't conform to this when it comes to open file
descriptors: even when standard output and/or error are
redirected somewhere when 'exit' is invoked, anything written
to them in the trap on EXIT goes to the script's original
stdout and stderr [4].
We can't dismiss this with a simple "it doesn't conform to
POSIX, so we don't care", because 'dash' is the default
/bin/sh in some of the more popular Linux distros.
- As far as I can tell, POSIX doesn't explicitly say anything
about the environment of trap actions for various signals.
In practice it seems that most shells behave sensibly and
preserve both open file descriptors and the state of '-x'
tracing for the traps on INT, TERM, and HUP, including even
'dash'. The exceptions are 'mksh' and 'lksh': they do
preserve '-x', but not the open file descriptors.
- When a test script run with '-x' tracing enabled is interrupted,
then it's very likely that the signal arrives mid-test, i.e.:
- while '-x' tracing is enabled, and, consequently, our trap
actions on INT, TERM, HUP, and EXIT will produce trace output
as well.
- while standard output and error are redirected to a log file,
to the test script's original standard output and error, or to
/dev/null, depending on whether the test script was run with
'--verbose-log', '-v', or neither. According to the above, we
can't rely on these redirections still be in effect when
running the traps on INT, TERM, HUP, and/or EXIT.
- When a test script is run with '--verbose-log', then the test
script is re-executed with its standard output and error piped
into 'tee', in order to send the "regular" non-verbose test's
output both to the terminal and to the log file. When the test is
interrupted, then the signal interrupts the downstream 'tee' as
well.
Putting these together, when a test script run with 'dash' and
'--verbose-log -x' is interrupted, then 'dash' tries to write the
trace output from the EXIT trap to the script's original standard
error, but it very likely can't, because the 'tee' downstream of the
pipe is interrupted as well. This causes the shell running the test
script to die because of SIGPIPE, without running any of the commands
in the EXIT trap.
Disable '-x' tracing in the trap on INT, TERM, and HUP to avoid this
issue, as it disables tracing in the chained trap on EXIT as well.
Wrap it in a '{ ... } 2>/dev/null' block, so the trace of the command
disabling the tracing doesn't go to standard error either [5].
Note that it's not only '-x' tracing that can be problematic, but any
shell builtin, e.g. 'echo', that writes to standard output or error in
the trap on EXIT, while a test running with 'dash' and '--verbose-log'
(even without '-x') is interrupted. As far as I can tell, this is not
an issue at the moment:
- The cleanup commands to stop the credential-helper, Apache, or
'p4d' don't use any such shell builtins.
- stop_git_daemon() does use 'say' and 'error', both wrappers around
'echo', but it redirects 'say' to fd 3, i.e. to the log file, and
while 'error' does write to standard output, it comes only after
the daemon was killed.
- The non-builtin commands that actually stop the daemons ('kill',
'apache2 -k stop', 'git credential-cache exit') are silent, so they
won't get SIGPIPE before finishing their job.
[1] The trap on EXIT must run cleanup commands, because we want to
stop any daemons when a test script run with '--immediate' fails
and exits early with error. By chaining up the trap on signals to
the trap on EXIT we can deal with cleanup commands a bit simpler,
because the tests involving daemons only have to set a single
trap.
[2] http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#trap
[3] The shells I tried: dash, Bash, ksh, ksh93, mksh, lksh, yash,
BusyBox sh, FreeBSD /bin/sh, NetBSD /bin/sh.
[4] $ cat trap-output.sh
#!/bin/sh
trap "echo output; echo error >&2" EXIT
{ exit; } >OUT 2>ERR
$ dash ./trap-output.sh
output
error
$ wc -c OUT ERR
0 OUT
0 ERR
On a related note, 'ksh', 'ksh93', and BusyBox sh don't conform to
the specs in this respect, either.
[5] This '{ set +x; } 2>/dev/null' trick won't help those shells that
show trace output for any redirections and don't preserve open
file descriptors for the trap on INT, TERM and HUP. The only such
shells I'm aware of are 'mksh' and 'lksh'.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
|
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|---|---|---|
| .github | ||
| block-sha1 | ||
| builtin | ||
| ci | ||
| compat | ||
| contrib | ||
| Documentation | ||
| ewah | ||
| git-gui | ||
| gitk-git | ||
| gitweb | ||
| mergetools | ||
| negotiator | ||
| perl | ||
| po | ||
| ppc | ||
| refs | ||
| sha1collisiondetection@232357eb2e | ||
| sha1dc | ||
| sha256 | ||
| t | ||
| templates | ||
| trace2 | ||
| vcs-svn | ||
| xdiff | ||
| .clang-format | ||
| .editorconfig | ||
| .gitattributes | ||
| .gitignore | ||
| .gitmodules | ||
| .mailmap | ||
| .travis.yml | ||
| .tsan-suppressions | ||
| abspath.c | ||
| aclocal.m4 | ||
| 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 | ||
| argv-array.c | ||
| argv-array.h | ||
| attr.c | ||
| attr.h | ||
| azure-pipelines.yml | ||
| banned.h | ||
| base85.c | ||
| bisect.c | ||
| bisect.h | ||
| blame.c | ||
| blame.h | ||
| blob.c | ||
| blob.h | ||
| branch.c | ||
| branch.h | ||
| builtin.h | ||
| bulk-checkin.c | ||
| bulk-checkin.h | ||
| bundle.c | ||
| bundle.h | ||
| cache-tree.c | ||
| cache-tree.h | ||
| cache.h | ||
| chdir-notify.c | ||
| chdir-notify.h | ||
| check_bindir | ||
| check-builtins.sh | ||
| checkout.c | ||
| checkout.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 | ||
| COPYING | ||
| credential-cache--daemon.c | ||
| credential-cache.c | ||
| credential-store.c | ||
| credential.c | ||
| credential.h | ||
| csum-file.c | ||
| csum-file.h | ||
| ctype.c | ||
| daemon.c | ||
| date.c | ||
| decorate.c | ||
| decorate.h | ||
| delta-islands.c | ||
| delta-islands.h | ||
| delta.h | ||
| detect-compiler | ||
| diff-delta.c | ||
| diff-lib.c | ||
| diff-no-index.c | ||
| diff.c | ||
| diff.h | ||
| diffcore-break.c | ||
| diffcore-delta.c | ||
| diffcore-order.c | ||
| diffcore-pickaxe.c | ||
| diffcore-rename.c | ||
| diffcore.h | ||
| dir-iterator.c | ||
| dir-iterator.h | ||
| dir.c | ||
| dir.h | ||
| editor.c | ||
| entry.c | ||
| environment.c | ||
| exec-cmd.c | ||
| exec-cmd.h | ||
| fast-import.c | ||
| fetch-negotiator.c | ||
| fetch-negotiator.h | ||
| fetch-object.c | ||
| fetch-object.h | ||
| fetch-pack.c | ||
| fetch-pack.h | ||
| 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 | ||
| 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-legacy-rebase.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-parse-remote.sh | ||
| git-quiltimport.sh | ||
| git-rebase--am.sh | ||
| git-rebase--common.sh | ||
| git-rebase--preserve-merges.sh | ||
| git-remote-testgit.sh | ||
| git-request-pull.sh | ||
| git-send-email.perl | ||
| git-sh-i18n.sh | ||
| git-sh-setup.sh | ||
| git-stash.sh | ||
| git-submodule.sh | ||
| git-svn.perl | ||
| GIT-VERSION-GEN | ||
| git-web--browse.sh | ||
| git.c | ||
| git.rc | ||
| gpg-interface.c | ||
| gpg-interface.h | ||
| graph.c | ||
| graph.h | ||
| grep.c | ||
| grep.h | ||
| hash.h | ||
| 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 | ||
| INSTALL | ||
| interdiff.c | ||
| interdiff.h | ||
| iterator.h | ||
| json-writer.c | ||
| json-writer.h | ||
| khash.h | ||
| kwset.c | ||
| kwset.h | ||
| levenshtein.c | ||
| levenshtein.h | ||
| LGPL-2.1 | ||
| 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 | ||
| Makefile | ||
| match-trees.c | ||
| mem-pool.c | ||
| mem-pool.h | ||
| merge-blobs.c | ||
| merge-blobs.h | ||
| merge-recursive.c | ||
| merge-recursive.h | ||
| merge.c | ||
| mergesort.c | ||
| mergesort.h | ||
| midx.c | ||
| 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-store.h | ||
| object.c | ||
| object.h | ||
| oidmap.c | ||
| oidmap.h | ||
| oidset.c | ||
| oidset.h | ||
| pack-bitmap-write.c | ||
| pack-bitmap.c | ||
| pack-bitmap.h | ||
| 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 | ||
| 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 | ||
| prompt.c | ||
| prompt.h | ||
| protocol.c | ||
| protocol.h | ||
| quote.c | ||
| quote.h | ||
| range-diff.c | ||
| range-diff.h | ||
| reachable.c | ||
| reachable.h | ||
| read-cache.c | ||
| README.md | ||
| rebase-interactive.c | ||
| rebase-interactive.h | ||
| ref-filter.c | ||
| ref-filter.h | ||
| reflog-walk.c | ||
| reflog-walk.h | ||
| refs.c | ||
| refs.h | ||
| refspec.c | ||
| refspec.h | ||
| RelNotes | ||
| remote-curl.c | ||
| remote-testsvn.c | ||
| remote.c | ||
| remote.h | ||
| replace-object.c | ||
| replace-object.h | ||
| repository.c | ||
| repository.h | ||
| rerere.c | ||
| rerere.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 | ||
| sha1-array.c | ||
| sha1-array.h | ||
| sha1-file.c | ||
| sha1-lookup.c | ||
| sha1-lookup.h | ||
| sha1-name.c | ||
| sha1dc_git.c | ||
| sha1dc_git.h | ||
| shallow.c | ||
| shell.c | ||
| shortlog.h | ||
| sideband.c | ||
| sideband.h | ||
| sigchain.c | ||
| sigchain.h | ||
| split-index.c | ||
| split-index.h | ||
| strbuf.c | ||
| strbuf.h | ||
| streaming.c | ||
| streaming.h | ||
| string-list.c | ||
| string-list.h | ||
| sub-process.c | ||
| sub-process.h | ||
| submodule-config.c | ||
| submodule-config.h | ||
| submodule.c | ||
| submodule.h | ||
| symlinks.c | ||
| tag.c | ||
| tag.h | ||
| tar.h | ||
| tempfile.c | ||
| tempfile.h | ||
| thread-utils.c | ||
| thread-utils.h | ||
| tmp-objdir.c | ||
| tmp-objdir.h | ||
| trace2.c | ||
| trace2.h | ||
| trace.c | ||
| trace.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 | ||
| 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 | ||
| 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 | ||
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-.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://public-inbox.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