06f3867865
When opening a MIDX bitmap, we the pack-bitmap machinery eagerly calls `prepare_midx_pack()` on each of the packs contained in the MIDX. This is done in order to populate the array of `struct packed_git *`s held by the MIDX, which we need later on in `load_reverse_index()`, since it calls `load_pack_revindex()` on each of the MIDX'd packs, and requires that the caller provide a pointer to a `struct packed_git`. When opening one of these packs fails, the pack-bitmap code will `die()` indicating that it can't open one of the packs in the MIDX. This indicates that the MIDX is somehow broken with respect to the current state of the repository. When this is the case, we indeed cannot make use of the MIDX bitmap to speed up reachability traversals. However, it does not mean that we can't perform reachability traversals at all. In other failure modes, that same function calls `warning()` and then returns -1, indicating to its caller (`open_bitmap()`) that we should either look for a pack bitmap if one is available, or perform normal object traversal without using bitmaps at all. There is no reason why this case should cause us to die. If we instead continued (by jumping to `cleanup` as this patch does) and avoid using bitmaps altogether, we may again try and query the MIDX, which will also fail. But when trying to call `fill_midx_entry()` fails, it also returns a signal of its failure, and prompts the caller to try and locate the object elsewhere. In other words, the normal object traversal machinery works fine in the presence of a corrupt MIDX, so there is no reason that the MIDX bitmap machinery should abort in that case when we could easily continue. Note that we *could* in theory try again to load a MIDX bitmap after calling `reprepare_packed_git()`. Even though the `prepare_packed_git()` code is careful to avoid adding a pack that we already have, `prepare_midx_pack()` is not. So if we got part of the way through calling `prepare_midx_pack()` on a stale MIDX, and then tried again on a fresh MIDX that contains some of the same packs, we would end up with a loop through the `->next` pointer. For now, let's do the simplest thing possible and fallback to the non-bitmap code when we detect a stale MIDX so that the complete fix as above can be implemented carefully. Signed-off-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.
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/, 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