a96d3cc3f6
We generally disallow null sha1s from entering the index, due to4337b5856(do not write null sha1s to on-disk index, 2012-07-28). However, we loosened that in83bd7437c(write_index: optionally allow broken null sha1s, 2013-08-27) so that tools like filter-branch could be used to repair broken history. However, we should make sure that these broken entries do not get propagated into new trees. For most entries, we'd catch them with the missing-object check (since presumably the null sha1 does not exist in our object database). But gitlink entries do not need reachability, so we may blindly copy the entry into a bogus tree. This patch rejects all null sha1s (with the same "invalid entry" message that missing objects get) when building trees from the index. It does so even for non-gitlinks, and even when "write-tree" is given the --missing-ok flag. The null sha1 is a special sentinel value that is already rejected in trees by fsck; whether the object exists or not, it is an error to put it in a tree. Note that for this to work, we must also avoid reusing an existing cache-tree that contains the null sha1. This patch does so by just refusing to write out any cache tree when the index contains a null sha1. This is blunter than we need to be; we could just reject the subtree that contains the offending entry. But it's not worth the complexity. The behavior is unchanged unless you have a broken index entry, and even then we'd refuse the whole index write unless the emergency GIT_ALLOW_NULL_SHA1 is in use. And even then the end result is only a performance drop (any write-tree will have to generate the whole cache-tree from scratch). The tests bear some explanation. The existing test in t7009 doesn't catch this problem, because our index-filter runs "git rm --cached", which will try to rewrite the updated index and barf on the bogus entry. So we never even make it to write-tree. The new test there adds a noop index-filter, which does show the problem. The new tests in t1601 are slightly redundant with what filter-branch is doing under the hood in t7009. But as they're much more direct, they're easier to reason about. And should filter-branch ever change or go away, we'd want to make sure that these plumbing commands behave sanely. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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.
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