From: Shreyansh Paliwal <shreyanshpaliwalcmsmn@gmail•com>
To: git@vger•kernel.org
Cc: christian.couder@gmail•com, karthik.188@gmail•com,
jltobler@gmail•com, ayu.chandekar@gmail•com,
siddharthasthana31@gmail•com
Subject: [GSOC][PROPOSAL]: Refactoring in order to reduce Git’s global state
Date: Fri, 6 Mar 2026 20:27:33 +0530 [thread overview]
Message-ID: <20260306151605.29330-1-shreyanshpaliwalcmsmn@gmail.com> (raw)
Hello all,
This is my first draft of GSoC 2026 proposal for the project
'Refactoring in order to reduce Git’s global state'.
Doc version can be read at:
https://docs.google.com/document/d/16MRNUv6dJi6vtNvI5Ro0WmHf20dRRBHjFLpmhAuaUOA/edit?usp=sharing
Any feedback or suggestions would be greatly appreciated.
Thanks for reading.
---
Refactoring in order to reduce Git's global state
Personal Information:
---------------------
Name: Shreyansh Paliwal
Email: Shreyanshpaliwalcmsmn@gmail•com
Alternate Email: Shreyansh.01014803123@it•mait.ac.in
Mobile No.: +91-9335120023
Education: GGSIPU, New Delhi, India
Year: III / IV
Degree: Bachelor of Technology in Information Technology
Github: https://github.com/shreyp135
Time-zone: UTC +5:30 (IST)
About Me:
---------
I am Shreyansh Paliwal, a pre-final year undergraduate student at Guru
Gobind Singh Indraprastha University, New Delhi, India. I am a technology
enthusiast, who began programming in 2018 with Java as my first language
and later transitioned to C/C++ in 2023 as my primary focus. I enjoy
exploring new technologies and programming languages, and I have developed
solid experience building applications using TypeScript, React.js, Node.js,
and AWS. I actively participate in technical events and have organized
multiple hackathons, tech-fests, and related activities at my college as
the SIG-Head of IOSD, a tech-focused student community.
I started using Git in 2023, which is also when I made my first open-source
contribution to the Git project. I was a winner of Augtoberfest 2024, an
open-source competition organized by C4GT India. Over the past several
months, I have been involved with the Git project, studying the codebase,
submitting patches, and incorporating review feedback. I am motivated to
improve the experience of Git for end users, and this project is an
excellent opportunity to continue that work.
Overview:
---------
Git relies heavily on global state for managing environment variables and
configuration data. In particular, many parts of the codebase depend on the
global struct repository instance, the_repository, which represents the
currently active repository. Instead of passing a repository instance
explicitly, several internal functions implicitly rely on this global
object. Additionally, various configuration derived values and
environment-related variables such as the_hash_algo, default_abbrev, and
comment_line_str are stored globally, most of them defined in
environment.c.
This design assumes that only one repository is active within a process at
a time. As a result, the repository state becomes shared across the entire
process, weakening isolation and making behavior implicitly dependent on
global context. Such global dependencies make the code harder to reason
about, test, and maintain, and can introduce subtle bugs when operations
interact with multiple repositories. They also limit long-term goals such
as safely supporting multiple repositories within a single process and
continuing Git’s ongoing libification efforts.
To address these issues, global environment and configuration state should
be refactored into better-scoped contexts. Repository-specific data can be
moved into struct repository or related structures, while
subsystem-specific state should be localized appropriately. Passing
repository instances explicitly through function interfaces will improve
modularity, reduce hidden dependencies, and make the codebase easier to
maintain while moving Git closer to supporting multiple repositories safely
within a single process.
The difficulty of this project is medium, and it is estimated to take 175
to 350 hours.
Pre-GSOC:
---------
I first explored the Git codebase in December 2023, when I submitted a
small patch fixing the wording of an error message that I noticed while
browsing the source code. At that time I had recently started using Git and
GitHub for version control in my projects, which sparked my curiosity about
how Git works internally.
A few months ago, when I had some free time from college, I decided to
start contributing to Git more actively. I built Git from source, read
parts of the documentation, and familiarized myself with the mailing list
workflow. While going through the documentation, I noticed a few
inconsistencies in the MyFirstContribution page and submitted patches to
fix them. I also completed a microproject involving a test cleanup, and
later worked on adding a warning for a quiet fallback.
During this process, I attempted to remove the usage of the_repository from
a file. However, after discussion on the mailing list, Phillip pointed out
that the change was not particularly useful in that context and could
introduce segfaults that would not justify the effort for builtin code.
Based on this feedback, I dropped that attempt and instead focused on
understanding the broader global state refactoring effort. To better
understand the project area, I studied previous patches and blog posts by
Ayush Chandekar and Olamide Bello, followed discussions on the mailing
list, and explored parts of the codebase such as the wt-status and worktree
subsystems. This helped me understand the ongoing effort to reduce Git’s
reliance on global state and motivated me to work further in this area.
The following is a list of my contributions, ordered from earliest to most
recent:
Patches for Git:
----------------
* test-lib-functions.sh: fix test_grep fail message wording
Status: Merged into master
Mailing List: https://lore.kernel.org/git/20231203171956.771-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: 37e8d795bed7b93d3f12bcdd3fbb86dfe57921e6
Log: This was my first patch to Git in 2023. While browsing the
source code and past issues, I noticed that even after
the test_i18ngrep function was deprecated, an error message
referring to test_grep was left behind. I updated the
wording to correctly reference test_i18ngrep.
* doc: MyFirstContribution: fix missing dependencies and clarify build steps
Status: Merged into master
Mailing List: https://lore.kernel.org/git/20260112195625.391821-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: 81021871eaa8b16a892b9c8791a0c905ab26e342
Log: While getting familiar with the codebase, I followed the
MyFirstContribution documentation and encountered a few
issues. Some include headers were missing, the synopsis
format was incorrect, and the explanation for -j$(nproc)
was absent. I submitted fixes to improve the clarity and
correctness of the documentation.
* t5500: simplify test implementation and fix git exit code suppression (Microproject)
Status: Merged into master
Mailing List: https://lore.kernel.org/git/20260121130012.888299-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: a824421d3644f39bfa8dfc75876db8ed1c7bcdbf
Log: This was completed as a microproject for GSoC. Instead of
constructing the pack protocol using a complex combination
of here-docs and echo commands, the patch captures command
outputs beforehand and uses the test-tool pkt-line pack
helper to construct the protocol input in a temporary file
before feeding it to git upload-pack.
* show-index: add warning and wrap error messages with gettext
Status: Merged into master
Mailing List: https://lore.kernel.org/git/20260130153603.290196-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: ea39808a22714b8f61b9472de7ef467ced15efea,
227e2cc4e1415c4aeadceef527dd33e478ad5ec3
Log: While exploring the code, I noticed a TODO comment suggesting
automatic hash detection. After discussion on the mailing
list, it was concluded that there was no future-proof
approach to implement this until a new index file format
came into use. Instead, an explicit warning was added rather
than silently falling back to SHA-1. Additionally, several
error messages were missing gettext wrapping, which was also
fixed.
* wt-status: reduce reliance on global state
Status: Merged into seen
Mailing List: https://lore.kernel.org/git/20260218175654.66004-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: a7cd24de0b3b679c16ae3ee8215af06aeea1e6a3,
9d0d2ba217f3ceefb0315b556f012edb598b9724,
4631e22f925fa2af8d8548af97ee2215be101409
Log: This has been the most significant patch series in my journey
so far. It began with a suggestion from Phillip to clean up
some the_repository usages in wt-status.c. I extended the
effort to remove all usages of the_repository and
the_hash_algo from the file. During review discussions, it
was suggested that some worktree API cleanup should happen
first, particularly regarding the representation of worktrees
as NULL. Some related changes were later moved to a separate
series, after which this refactoring proceeded.
* worktree: change representation and usage of primary worktree
Status: Continued by Phillip Wood [1]
Mailing List: https://lore.kernel.org/git/20260213120529.15475-1-shreyanshpaliwalcmsmn@gmail.com/
Log: This worktree API cleanup series started while I was working
on wt-status. The intention was to modify the representation
of the current worktree so that struct worktree would not be
NULL. During discussion, Phillip clarified that NULL actually
represents the current worktree rather than the primary
worktree. Since Phillip already had a patch based on the right
logic, he continued the series and it was eventually merged
into master.
* tree-diff: remove the usage of the_hash_algo global
Status: Merged into master
Mailing List: https://lore.kernel.org/git/20260220175331.1250726-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: 1e50d839f8592daf364778298a61670c4b998654
Log: This was a straightforward patch that removed the remaining
usages of the global the_hash_algo in tree-diff.c by using the
repository’s local instance instead.
* send-email: UTF-8 encoding in subject line
Status: Merged into seen
Mailing List: https://lore.kernel.org/git/20260228112210.270273-1-shreyanshpaliwalcmsmn@gmail.com/
Merge Commit: c52f085a477c8eece87821c5bbc035e5a900eb12
Log: This patch was motivated by an issue I personally encountered
while sending a GSoC discussion email [2]. Initially the
change only modified the wording of the prompt, but after
discussion on the mailing list it was extended to include
proper validation to prevent invalid charset encodings from
being used in git send-email and to reduce confusion.
* Remove global state from editor.c
Status: Waiting for further feedback
Mailing List: https://lore.kernel.org/git/20260301105228.1738388-1-shreyanshpaliwalcmsmn@gmail.com/
Log: This was based on my doubt on localizing editor_program in
editor.c [2]. The patch received mixed feedback from
contributors and is currently awaiting additional guidance
from mentor and/or maintainer regarding the appropriate
direction.
Patches for git.github.io:
--------------------------
* SoC-2026-ideas: Remove an extra backtick
Status: merged into master
PR Link: https://github.com/git/git.github.io/pull/831
Merge Commit: c1e4aa87a54430953eaa7355061139fdf1ff6796
Log: Minor Typo fix.
* rn-132: fixed 2 typos
Status: merged into master
PR Link: https://github.com/git/git.github.io/pull/832
Merge Commit: 92876114d855d472ce2e0e5337e72a4b97b81681
Log: Fixed typos in Git Rev News Edition 132.
I have also been involved in additional discussions on the Git mailing
list [3][4][5][6].
History / Background:
--------------------
Efforts to reduce Git’s reliance on global state started when several Git
subsystems began moving toward libification, where Git’s internal
functionality could be reused as a library. Early examples of this
direction include major patch series such as the libification of git
mailinfo by Junio [7] and git apply by Christian [8]. These large patch
series exposed the limitations of relying on process-wide global state and
highlighted the need for better encapsulation of repository-related data.
One important step in this direction was the introduction of struct
repository, through refactoring work by Stefan Beller [9] and Brandon
Williams [10]. The motivation behind this structure was to centralize
repository-related state instead of relying on scattered global variables.
This change improved code clarity and made it easier to reason about Git’s
internal behavior. It also laid the groundwork for future improvements such
as safer multithreading and the possibility of handling submodules within
the same process. Later, additional refactoring work by Patrick further
removed reliance on the global the_repository in config [11] and path [12]
subsystems. As part of this work, several variables were consolidated into
environment.c from config.c so that environment-related state could be
managed in a single location [13]. The macro #define
USE_THE_REPOSITORY_VARIABLE was also introduced to help transition code
away from implicit global repository access [14].
This project area was further explored during GSoC 2025 by Ayush Chandekar
[15], who continued removing usages of the_repository across different parts
of the codebase and relocated several global configuration variables (such as
core_preload_index and merge_log_config) into repository-scoped structures.
More recently, Olamide Bello, during the Outreachy program, made significant
progress in improving how configuration values are stored [16] [17]. His work
introduced a new structure, repo_config_values, which stores repository
specific configuration values, linked to struct repository. This allows
configuration values to be associated with a specific repository instance
rather than stored globally. Along with this, a private structure
config_values_private was added to support initialization and internal
handling of these values. During discussions around these changes, an
important design consideration also emerged, moving global variables directly
into repository structures or introducing lazy loading helpers can lead to
user experience regressions if configuration errors are detected later.
These efforts collectively form the foundation of the ongoing work to
gradually remove Git’s reliance on global state and move toward a more
modular, repository-scoped architecture.
Proposed Plan:
-------------
I started exploring the codebase by browsing relevant files and identifying
global variables by temporarily removing the USE_THE_REPOSITORY_VARIABLE
macro. My primary focus was on core library files rather than builtin code
[18]. Through this exploration, I observed that a large number of files still
depend on the_repository.
To tackle this project systematically, I propose classifying these files into
two categories:
1. Files using the_repository or the_hash_algo where a repository instance
already exists: These files rely on global variables even though a
struct repository instance is available somewhere in the call stack. In
such cases, the refactor primarily involves passing the repository
instance through the function call stack and replacing the global
usages. In some cases, a repository instance may not be directly
available in the file itself. In those situations, I will trace the
callers and propagate repository instances from higher levels in the call
hierarchy. Examples of such files include, alias.c, archive*.c,
walker.c, xdiff-interface.c. These cases generally require localized
refactoring and are good candidates for incremental patches.
2. Files relying on other global variables defined in environment.c: Some
files rely on additional global variables which are parsed and accessed
through environment.c. In these cases, there is no existing
repository-scoped instance, which makes refactoring slightly more
technical. Examples include, wt-status.c (default_abbrev,
comment_line_str), apply.c (has_symlink, ignore_case,
trust_executable_bit, apply_default_whitespace,
apply_default_ignorewhitespace). For such variables, I plan to evaluate
whether they should be moved into a repository-scoped structure (e.g.,
repo_settings, repo_config_values), or they should instead be localized
and passed explicitly where needed. The appropriate approach will depend
on how widely the variable is used and whether it logically fits in the
multi-repository standpoint.
I plan to begin with the first category, addressing straightforward
refactors file by file. In parallel, I will analyze and work on specific
groups of global variables from the second category, designing appropriate
repository-scoped replacements.
The end goal is to remove reliance on global state and eventually eliminate
the USE_THE_REPOSITORY_VARIABLE macro from these files.
Project Timeline:
----------------
* Community Bonding (Until May 24):
- Discuss the project direction and design approaches with mentors.
- Identify and prioritize two main areas of work:
+ files that rely on the_repository.
+ global variables defined in environment.c.
- Study the previous patches by Olamide Bello and Ayush in depth and
also discuss with them about their approaches and challenges.
- Interact with all the people involved in this work to better
understand design decisions and potential pitfalls.
- Experiment with small RFC patches, if needed to validate approaches.
* Coding period (May 25 - August 16):
- Review the work done by Olamide Bello on moving values parsed by
git_default_config() into the repo_config_values structure and
identify any remaining tasks.
- Complete remaining cleanup or refactoring related to the worktree API,
if left any [19].
- Identify straightforward refactors to remove usages of the_repository
in files such as xdiff-interface.c, archive*.c, fsmonitor*.c etc.
- Work file by file with the goal of eliminating
#define USE_THE_REPOSITORY_VARIABLE by replacing global usages
with explicit repository instances.
- Concurrently maintain at least two parallel patch series:
+ Small / straightforward refactors and replacements like
the_hash_algo or the_repostitory.
+ Larger structural refactors involving globals such as
DEFAULT_ABBREV, comment_line_str etc.
- Publish weekly or biweekly blog updates documenting progress and design
decisions.
* Final week (august 17 - august 24):
- Address any remaining tasks or pending patches.
- Recieve final feedback from mentors and reviewers.
- Prepare a detailed report summarizing the work completed during the project.
Blogging:
---------
I believe blogging is an important part of any open-source project. It
helps others understand the ongoing work and also enables the contributor
to develop a deeper understanding and keep a better track of their own
progress. I experienced this firsthand, early in my journey I was unsure
about various aspects, but reading the blogs of Ayush and Olamide Bello
gave me valuable insight into the contributor perspective and their overall
work.
With the goal of helping future contributors in a similar way, I plan to
document my journey and project progress through regular blog posts. I will
publish updates on a weekly or biweekly basis, depending on the amount of
meaningful progress made. I have set up my blogging area on Medium, and my
posts will be available at [20].
Availability:
-------------
The main coding period runs from June to August. Most of June and July
coincide with my summer vacation, which allows me to dedicate significant
time to the project. My final exams are scheduled for May and will last
approximately one week, but they will be completed before the coding period
begins and should not affect my availability.
During June and July, I will be able to dedicate around 40 hours per week to
the project. In August, when my regular semester resumes, I expect to
contribute approximately 25–30 hours per week.
I do not have any other exams, internships, or planned vacations during the
coding period. Apart from this project, I have no other major commitments
for the summer.
I will keep the community regularly updated on my progress throughout the
project. My primary mode of communication will be email, and I will also be
available for calls or meetings if/when required. My preferred availability
window is 13:00–19:00 UTC.
Post GSoC:
----------
Being part of the Git community and contributing to the codebase has been a
very valuable experience for me. The process of understanding Git’s internals,
submitting patches, and receiving feedback on the mailing list has helped me
grow significantly as a developer. The feeling of working on code that is used
by millions of developers and companies around the world is very rewarding.
I plan to remain involved with the Git community even after GSoC by continuing
to contribute patches, review code, and participate in discussions to help make
Git better for end users. The work on refactoring Git’s global state is part of
a long-term effort, and I would love to continue working on it beyond the GSoC
timeline.
I would also be happy to mentor, co-mentor, or volunteer in the future to help
new and upcoming contributors whenever I get the chance. I see GSoC as the
starting point of a long-term relationship with the Git community.
Closing & Appreciation:
-----------------------
I would like to thank the Git community for the excellent documentation and the
welcoming environment. I am also grateful for the patience and guidance shown
in the feedback and discussions on the mailing list by Junio, Phillip, Karthik,
Ben, and others, which have helped me improve my understanding and contributions.
I also read blogs and proposals by Ayush, Lucas, Kousik Sanagavarapu, and Olamide
Bello, which provided valuable insights and helped shape my approach to contributing.
Thank you for reviewing my proposal :)
References:
-----------
[1]- https://lore.kernel.org/git/cover.1771511192.git.phillip.wood@dunelm.org.uk/
[2]- https://lore.kernel.org/git/20260304145823.189440-1-shreyanshpaliwalcmsmn@gmail.com/T/#m65b9b4547036991a7b7f3c861b9663428891f588
[3]- https://lore.kernel.org/git/20260114143238.536312-1-shreyanshpaliwalcmsmn@gmail.com/
[4]- https://lore.kernel.org/git/20260115211609.17420-1-shreyanshpaliwalcmsmn@gmail.com/
[5]- https://lore.kernel.org/git/20260204111343.71975-1-shreyanshpaliwalcmsmn@gmail.com/
[6]- https://lore.kernel.org/git/20260205131132.44282-1-shreyanshpaliwalcmsmn@gmail.com/
[7]- https://lore.kernel.org/git/1444778207-859-1-git-send-email-gitster@pobox.com/
[8]- https://lore.kernel.org/git/20160511131745.2914-1-chriscool@tuxfamily.org/
[9]- https://lore.kernel.org/git/20180205235508.216277-1-sbeller@google.com/
[10]- https://lore.kernel.org/git/20170531214417.38857-1-bmwill@google.com/
[11]- https://lore.kernel.org/git/cover.1715339393.git.ps@pks.im/
[12]- https://lore.kernel.org/git/20250206-b4-pks-path-drop-the-repository-v1-16-4e77f0313206@pks.im/
[13]- https://lore.kernel.org/git/20250717-pks-config-wo-the-repository-v1-20-d888e4a17de1@pks.im/
[14]- https://lore.kernel.org/git/cover.1718347699.git.ps@pks.im/
[15]- https://ayu-ch.github.io/2025/08/29/gsoc-final-report.html
[16]- https://cloobtech.hashnode.dev/week-5-and-6-design-reviews-rfcs-and-refining-the-path-forward
[17]- https://lore.kernel.org/all/cover.1771258573.git.belkid98@gmail.com/
[18]- https://lore.kernel.org/git/7b5dd0c4-0ca0-458e-89db-621a70dac9ae@gmail.com/
[19]- https://lore.kernel.org/git/20260217163909.55094-1-shreyanshpaliwalcmsmn@gmail.com/
[20]- https://medium.com/@shreyanshpaliwal18
next reply other threads:[~2026-03-06 15:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-06 14:57 Shreyansh Paliwal [this message]
2026-03-07 10:33 ` [GSOC][PROPOSAL]: Refactoring in order to reduce Git’s global state Christian Couder
2026-03-07 12:46 ` Shreyansh Paliwal
2026-03-07 20:04 ` [GSOC][PROPOSAL v2]: " Shreyansh Paliwal
2026-03-09 14:42 ` Christian Couder
2026-03-10 14:58 ` Shreyansh Paliwal
2026-03-20 18:12 ` [GSOC][PROPOSAL v3]: " Shreyansh Paliwal
-- strict thread matches above, loose matches on Subject: below --
2026-03-17 17:54 [GSoC Proposal] Refactoring in order to reduce Git's " Francesco Paparatto
2026-03-21 13:36 ` Christian Couder
2026-03-21 13:56 ` Francesco Paparatto
2026-03-21 16:32 ` Junio C Hamano
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