bfc763df77
Correct tracking of the 'cache_bottom' for cases where sparse directories are present in the index. BACKGROUND ---------- The 'unpack_trees_options.cache_bottom' is a variable that tracks the in-progress "bottom" of the cache as 'unpack_trees()' iterates through the contents of the index. Most importantly, this value informs the sequential return values of 'next_cache_entry()' which, in the "diff cache" usage of 'unpack_callback()', are either unpacked as-is or are passed into the diff machinery. The 'cache_bottom' is intended to track the position of the first entry in the index that has not yet been diffed or unpacked. It is advanced in two main ways: either it is incremented when an index entry is marked as "used" (in 'mark_ce_used()'), indicating that it was unpacked or diffed, or when a directory is unpacked, in which case it is increased by an amount equaling the number of index entries inside that tree. In 17a1bb570b (unpack-trees: preserve cache_bottom, 2021-07-14), it was identified that sparse directories posed a problem to the above 'cache_bottom' advancement logic - because a sparse directory was both an index entry that could be "used" and a directory that can be unpacked, the 'cache_bottom' would be incremented too many times. To solve this problem, the 'mark_ce_used()' advancement of 'cache_bottom' was skipped for sparse directories. INCORRECT CACHE_BOTTOM TRACKING ------------------------------- Skipping the 'cache_bottom' advancement for sparse directories in 'mark_ce_used()' breaks down in two cases: 1. When the 'unpack_trees()' operation is *not* a "cache diff" (because the directory contents-based incrementing of 'cache_bottom' does not happen). 2. When a cache diff is performed with a pathspec (because 'unpack_index_entry()' will unpack a sparse directory not matched by the pathspec without performing the directory contents-based increment). The former luckily does not appear to affect 'git' behavior, likely because 'cache_bottom' is largely unused (non-"cache diff" 'unpack_trees()' uses 'find_index_entry()' - rather than 'next_cache_entry()' - to find the index entries to unpack). The latter, however, causes 'cache_bottom' to "lag behind" its intended position by an amount equal to the number of sparse directories unpacked so far with 'unpack_index_entry()'. If a repository is structured such that any sparse directories are ordered lexicographically *after* any pathspec-matching directories, though, this issue won't present any adverse behavior. This was the case with the 't1092-sparse-checkout-compatibility.sh' tests before the addition of the 'before/' sparse directory (ordered *before* the in-cone 'deep/' directory), therefore sidestepping the issue. Once the 'before/' directory was added, though, 'cache_bottom' began to lag behind its intended position, causing 'next_cache_entry()' to return index entries it had already processed and, ultimately, an incorrect diff. CORRECTING CACHE_BOTTOM ----------------------- The problems observed in 't1092' come from 'cache_bottom' lagging behind in cases where the cache tree-based advancement doesn't occur. To solve this, then, the fix in 17a1bb570b is "reversed"; rather than skipping 'cache_bottom' advancement in 'mark_ce_used()', we skip the directory contents-based advancement for sparse directories. Now, every index entry can be accounted for in 'cache_bottom': * if you're working with a single index entry, 'cache_bottom' is incremented in 'mark_ce_used()' * if you're working with a directory that contains index entries (but is not one itself), 'cache_bottom' is incremented by the number of entries in that directory. Finally, change the 'test_expect_failure' tests in 't1092' failing due to this bug back to 'test_expect_success'. Signed-off-by: Victoria Dye <vdye@github.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