b27ccae34b
Since the point of --verify-objects is to actually load and checksum the
bytes of each object, optimizing out reads using the commit graph runs
contrary to our goal.
The most targeted way to implement this would be for the revision
traversal code to check revs->verify_objects and avoid using the commit
graph. But it's difficult to be sure we've hit all of the correct spots.
For instance, I started this patch by writing the first of the included
test cases, where the corrupted commit is directly on rev-list's command
line. And that is easy to fix by teaching get_reference() to check
revs->verify_objects before calling lookup_commit_in_graph().
But that doesn't cover the second test case: when we traverse to a
corrupted commit, we'd parse the parent in process_parents(). So we'd
need to check there, too. And it keeps going. In handle_commit() we
sometimes parses commits, too, though I couldn't figure out a way to
trigger it that did not already parse via get_reference() or tag
peeling. And try_to_simplify_commit() has its own parse call, and so on.
So it seems like the safest thing is to just disable the commit graph
for the whole process when we see the --verify-objects option. We can do
that either in builtin/rev-list.c, where we use the option, or in
revision.c, where we parse it. There are some subtleties:
- putting it in rev-list.c is less surprising in some ways, because
there we know we are just doing a single traversal. In a command
which does multiple traversals in a single process, it's rather
unexpected to globally disable the commit graph.
- putting it in revision.c is less surprising in some ways, because
the caller does not have to remember to disable the graph
themselves. But this is already tricky! The verify_objects flag in
rev_info doesn't do anything by itself. The caller has to provide an
object callback which does the right thing.
- for that reason, in practice nobody but rev-list uses this option in
the first place. So the distinction is probably not important either
way. Arguably it should just be an option of rev-list, and not the
general revision machinery; right now you can run "git log
--verify-objects", but it does not actually do anything useful.
- checking for a parsed revs.verify_objects flag in rev-list.c is too
late. By that time we've already passed the arguments to
setup_revisions(), which will have parsed the commits using the
graph.
So this commit disables the graph as soon as we see the option in
revision.c. That's a pretty broad hammer, but it does what we want, and
in practice nobody but rev-list is using this flag anyway.
The tests cover both the "tip" and "parent" cases. Obviously our hammer
hits them both in this case, but it's good to check both in case
somebody later tries the more focused approach.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
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.
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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
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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).
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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