[{"data":1,"prerenderedAt":815},["ShallowReactive",2],{"/en-us/blog/gitlabs-contributions-to-git-2-44-0":3,"navigation-en-us":38,"banner-en-us":448,"footer-en-us":458,"blog-post-authors-en-us-Patrick Steinhardt":700,"blog-related-posts-en-us-gitlabs-contributions-to-git-2-44-0":714,"blog-promotions-en-us":751,"next-steps-en-us":805},{"id":4,"title":5,"authorSlugs":6,"body":8,"categorySlug":9,"config":10,"content":14,"description":8,"extension":26,"isFeatured":12,"meta":27,"navigation":28,"path":29,"publishedDate":20,"seo":30,"stem":34,"tagSlugs":35,"__hash__":37},"blogPosts/en-us/blog/gitlabs-contributions-to-git-2-44-0.yml","Gitlabs Contributions To Git 2 44 0",[7],"patrick-steinhardt",null,"open-source",{"slug":11,"featured":12,"template":13},"gitlabs-contributions-to-git-2-44-0",false,"BlogPost",{"title":15,"description":16,"authors":17,"heroImage":19,"date":20,"body":21,"category":9,"tags":22},"GitLab's contributions to Git 2.44.0","Find out the topics that GitLab’s Git team – as well as the wider community – contributed to the latest Git release, including fast scripted rebases via git-replay.",[18],"Patrick Steinhardt","https://res.cloudinary.com/about-gitlab-com/image/upload/v1749666069/Blog/Hero%20Images/AdobeStock_639935439.jpg","2024-02-26","The Git project recently released [Git 2.44.0](https://git-scm.com/downloads). In this blog post, we will highlight the contributions made by GitLab's Git team, as well as those from the wider Git community.\n\n## Fast scripted rebases via `git-replay`\n\nThe `git-rebase` command can be used to reapply a set of commits onto a different base commit. This can be quite useful when you have a feature branch where the main branch it was originally created from has advanced since creating the feature branch.\n\nIn this case, `git-rebase` can be used to reapply all commits of the feature branch onto the new commits of the main branch.\n\nSuppose you have the following commit history with the main development branch `main` and your feature branch `feature`:\n\n![main and feature branch](https://res.cloudinary.com/about-gitlab-com/image/upload/v1749678099/Blog/Content%20Images/Screenshot_2024-02-20_at_2.15.37_PM.png)\n\nYou have originally created your feature branch from `m-2`, but since then the `main` branch has gained two additional commits. Now `git-rebase` can be used to reapply your commits `f-1` and `f-2` on top of the newest commit `m-4`:\n\n![applying git-rebase](https://res.cloudinary.com/about-gitlab-com/image/upload/v1749678099/Blog/Content%20Images/Screenshot_2024-02-20_at_2.16.28_PM.png)\n\nYou can see this functionality in GitLab when you create a merge request. When you want to reapply the commits of your merge request onto new commits in the target branch, all you have to do is [to create a comment that contains the `/rebase` command](https://docs.gitlab.com/topics/git/git_rebase/#rebase-from-the-ui). The magic then happens behind the scenes.\n\nThere is one problem though: `git-rebase` only works on repositories that have a worktree (a directory where a branch, tag or commit has been checked out). The repositories we host at GitLab are “bare” repositories, which don’t have a worktree. This means that the files and directories tracked by your commits are only tracked as Git objects in the `.git` directory of the repository. This is mostly done to save precious disk space and speed up operations.\n\nIn the past, we used [libgit2](https://libgit2.org/) to implement rebases. But for various reasons, we decided to remove this dependency in favor of only using Git commands to access Git repositories. But this created a problem for\nus because we could neither use libgit2 nor `git-rebase` to perform rebases. While we could create an ad-hoc worktree to use `git-rebase`, this would have been prohibitively expensive in large monorepos.\n\nLuckily, [Elijah Newren](https://www.linkedin.com/in/elijah-newren-0a41665/) has upstreamed a new merge algorithm called `merge-ort` in Git 2.33. Despite being significantly faster than the old `recursive` merge strategy in almost all cases, it also has the added benefit that it can perform merges in-memory. In practice, this also allows us to perform such rebases in-memory.\n\nEnter `git-replay`, which is a new command that does essentially the same thing as `git-rebase` but in-memory, thus not requiring a worktree anymore. This is an\nimportant building block to allow us to develop faster rebasing of merge requests in the future.\n\nYou may ask: Why a new command instead of updating `git-rebase`? The problem here was that `git-rebase` is essentially a user-focused command (also called a\n\"porcelain\" command in Git). Thus it performs several actions that are not required by a script at all, like, for example, executing hooks or checking out files into the worktree. The new `git-replay` command is a script-focused\ncommand (also called a \"plumbing\" command in Git) and has a different set of advantages and drawbacks. Furthermore, besides doing rebases, we plan to use it to do cherry-picks and reverts in the future, too.\n\nThis topic was a joint effort by [Elijah Newren](https://www.linkedin.com/in/elijah-newren-0a41665/) and\n[Christian Couder](https://www.gitlab.com/chriscool).\n\n## Commit-graph object existence checks\n\nYou may know that each commit can have an arbitrary number of parents:\n\n- The first commit in your repository has no parents. This is the \"root\" commit.\n- Normal commits have a single parent.\n- Merge commits have at least two, but sometimes even more than two parents.\n\nThis parent relationship is part of what forms the basis of Git's object model and establishes the object graph. If you want to traverse this object graph, Git must look up an entry point commit and from there walk the parent chain of commits.\n\nTo fully traverse history from the newest to the oldest commit, you must look up and parse all commit objects in between. Because repositories can consist of hundreds of thousands or even millions of such commits, this can be\nquite an expensive operation. But users of such repositories still want to be able to, for example, search for a specific commit that changes a specific file\nwithout waiting several minutes for the search to complete.\n\nThe Git project introduced a commit-graph data structure a long time ago that essentially caches a lot of the parsed information in a more accessible data structure. This commit-graph encodes the parent-child relation and some additional information, like, for example, a [bloom filter](https://en.wikipedia.org/wiki/Bloom_filter) of changed\nfiles.\n\nThis commit-graph is usually updated automatically during repository housekeeping. Because housekeeping only runs every so often, the commit-graph can be missing entries for recently added commits. This is perfectly fine and expected to happen, and Git knows to instead look up and parse the commit object in such a case.\n\nNow, the reverse case also theoretically exists: The commit-graph contains cached information of an object that does not exist anymore because it has been deleted without regenerating the commit-graph. The consequence would\nbe that lookups of this commit succeed even though they really shouldn't. To avoid this, in Git 2.43.0, we upstreamed a change into Git that detects commits\nthat exist in the commit-graph but no longer in the object database.\n\nThis change requires us to do an existence check for every commit that we parse via the commit-graph. Naturally, this change leads to a performance regression, which was measured to be about 30% in the worst case. This was\ndeemed acceptable though, because it is better to return the correct result slowly than to return the wrong result quickly. Furthermore, the commit-graph still results in a significant performance improvement compared to not using the commit-graph at all. To give users an escape hatch in case they do not want this performance regression, we also introduced a `GIT_COMMIT_GRAPH_PARANOIA` environment variable that can be used to disable this check.\n\nAfter this change was merged and released though, we heard of cases where the impact was even worse than 30%: counting the number of commits via `git rev-list --count` in the Linux repository regressed by about 100%. After some\ndiscussion upstream, we changed the default so that we no longer verify commit existence for the commit-graph to speed up such queries again. Because repository housekeeping should ensure that commit-graphs are consistent, this change should stop us from needlessly pessimizing this uncommon case.\n\nThis change was implemented by\n[Patrick Steinhardt](https://gitlab.com/pks-gitlab).\n\n## Making Git ready for a new ref backend\n\nA common theme among our customers is that large monorepos with many refs create significant performance problems with many workloads. The range of problems here are manyfold, but the more refs a repository has, the more pronounced the problems become.\n\nMany of the issues are inherent limitations of the way Git stores refs. The so-called `files` ref backend uses a combination of two mechanisms:\n- \"Loose refs\" are simple files that contain the object ID they point to.\n- \"Packed refs\" are a single file that contains a collection of refs.\n\nWhenever you update or create a ref, Git creates them as a loose ref. Every once in a while, repository housekeeping then compresses all loose refs into the `packed-refs` file and deletes the corresponding loose refs. A typical repo looks as follows:\n\n```shell\n $ git init --ref-format=files repo\nInitialized empty Git repository in /tmp/repo/.git/\n $ cd repo/\n $ git commit --allow-empty --message \"initial commit\"\n $ tree .git/\n.git/\n├── config\n├── HEAD\n├── index\n└── refs\n\t├── heads\n\t│   └── main\n\t└── tags\n $ cat .git/HEAD\nref: refs/heads/main\n $ cat .git/refs/heads/main\nbf1814060ed3a88bd457ac4dca055d000ffe4482\n\n $ git pack-refs --all\n $ cat .git/packed-refs\n# pack-refs with: peeled fully-peeled sorted\nbf1814060ed3a88bd457ac4dca055d000ffe4482 refs/heads/main\n```\n\nWhile this model has served the Git project quite well, relying on a filesystem like this has several limitations:\n- Deleting a single ref requires you to rewrite the `packed-refs` file, which can be gigabytes in size.\n- It is impossible to do atomic reads because you cannot atomically scan multiple files at once when a concurrent writer may modify some refs.\n- It is impossible to do atomic writes because creating or updating several refs requires you to write to several files.\n- Housekeeping via `git-pack-refs` does not scale well because of its all-into-one repacking nature.\n- The storage format of both loose and packed refs is inefficient and wastes disk space.\n- Filesystem-specific behavior can be weird and may restrict which refs can be created. For example, Case-insensitivity on filesystems like FAT32 can cause issues, when trying to create two refs with the same name that only differ in their case.\n\nSeveral years ago, [Shawn Pearce](https://sfconservancy.org/blog/2018/jan/30/shawn-pearce/) had proposed the \"reftable\" format as an alternative new format to store refs in a repository. This new format was supposed to help with most or all of the above issues and is essentially a\nbinary format specifically catered towards storing references in Git.\n\nThis new \"reftable\" format has already been implemented by\n[JGit](https://www.eclipse.org/jgit/) and is used extensively by the [Gerrit project](https://www.gerritcodereview.com/). And, in 2021, [Han-Wen Nienhuys](https://www.linkedin.com/pub/dir/han-wen/nienhuys) upstreamed a library to read and write reftables into the Git project. What is still missing though is the backend that ties together the reftable library and\nGit, and unfortunately progress has stalled here. As we experience much of the pain that the reftable format is supposed to address, we decided to take over the work from Han-Wen and continue the upstreaming process.\n\nBefore we can upstream the reftable backend itself though, we first had to prepare several parts of Git for such a new backend. While the Git project already has a concept of different ref backends, the boundaries were very blurry because until now there only exists a single \"files\" backend.\n\nThe biggest contribution by GitLab in this release was thus a joint effort to prepare all the parts of Git for the new backend that were crossing boundaries:\n- Some commands used to read or write refs directly via the filesystem without going through the ref backend.\n- The ref databases of worktrees created via `git-worktree` were initialized ad-hoc instead of going through the ref backend.\n- Cloning a repository created the ref database with the wrong object format when using SHA256. This did not matter with the \"files\" backend because the format was not stored anywhere by the ref backend itself. But because the reftable backend encodes the format into its binary format, this was a problem.\n- Many tests read or write refs via the filesystem directly.\n- We invested quite some time already into bug fixing and performance optimizations for the reftable library itself.\n- We introduced a new `refStorage` extension that tells Git in which format the repository stores its refs. This can be changed when creating a new repository by specifying `--ref-format` flag in `git-init` or `git-clone`. For now, only the “files” format is supported.\n\nThe overarching goal was to get the work-in-progress reftable backend into a state where it passes the complete test suite. And even though the reftable backend is not yet part of Git 2.44.0, I am happy to report that we have\nsucceeded in this goal: Overall, we have contributed more than 150 patches to realize it. Given the current state, we expect that the new reftable backend will become available with Git v2.45.0.\n\nWe will not cover the new reftable format in this post because it is out of scope, but stay tuned for more details soon!\n\nThis project was a joint effort by\n[John Cai](https://gitlab.com/jcaigitlab),\n[Justin Tobler](https://gitlab.com/justintobler),\n[Karthik Nayak](https://gitlab.com/knayakgl),\n[Stan Hu](https://gitlab.com/stanhu),\n[Toon Claes](https://gitlab.com/toon),\nand [Patrick Steinhardt](https://gitlab.com/pks-gitlab), who has led the effort. Credit also goes to\n[Shawn Pearce](https://sfconservancy.org/blog/2018/jan/30/shawn-pearce/) as original inventor of the format and [Han-Wen Nienhuys](https://www.linkedin.com/pub/dir/han-wen/nienhuys) as the\nauthor of the reftable library.\n\n## Support for GitLab CI\n\nAs all the preparations for the new `reftable` backend demonstrate, we have significantly increased our investments into the long-term vision and health of\nthe Git project. And because a very important part of our product depends on the Git project to remain healthy, we want to continue investing into the Git project like this.\n\nFor us, this means that it was high time to improve our own workflows in the context of the Git project. Naturally, we were already using GitLab CI as part of the process instead of the GitHub Workflows support that existed in\nthe Git project. But we were using a [`.gitlab-ci.yml` definition](https://docs.gitlab.com/ci/yaml/) that was not part of the upstream repository and instead maintained outside the Git project.\n\nWhile this worked reasonably well, there were two significant downsides:\n- Test coverage was significantly lower than that of the GitHub Workflows definition. Notably, we did not test on macOS, had no static analysis, and didn't test with non-default settings. This often led to failures in the GitHub Workflows pipeline that we could have detected earlier if we had better CI integration.\n- Other potential contributors to Git who may already be using GitLab on a daily basis didn't have easy access to a GitLab CI pipeline.\n\nTherefore, we decided to upstream a new GitLab CI definition that integrates with the preexisting CI infrastructure that the Git project already had. Because we reuse a lot of pre-existing infrastructure, this ensures that both GitLab CI and GitHub Workflows run tests mostly in the same way.\n\nAnother benefit of GitLab CI support is that, for the first time, we now also exercise an architecture other than `x86_64` or `i686`: the [macOS runners we provide at GitLab.com](https://docs.gitlab.com/ci/runners/saas/macos_saas_runner.ht/ ml) use an Apple M1, which is based on the `arm64` architecture.\n\nThis change was contributed by [Patrick Steinhardt](https://gitlab.com/pks-gitlab).\n\n## More to come\n\nThis blog post gives just a glimpse into what has happened in the Git project, which lies at the heart of [source code management](https://about.gitlab.com/solutions/source-code-management/) at GitLab. Stay tuned for more insights into future contributions and the reftable backend in particular!",[23,24,25],"git","open source","CI","yml",{},true,"/en-us/blog/gitlabs-contributions-to-git-2-44-0",{"title":15,"description":16,"ogTitle":15,"ogDescription":16,"noIndex":12,"ogImage":19,"ogUrl":31,"ogSiteName":32,"ogType":33,"canonicalUrls":31},"https://about.gitlab.com/blog/gitlabs-contributions-to-git-2-44-0","https://about.gitlab.com","article","en-us/blog/gitlabs-contributions-to-git-2-44-0",[23,9,36],"ci","RNPYUU72ALh7ZCpIMWwVvosbiPdIvUUkVw-9AGdhOd8",{"data":39},{"logo":40,"freeTrial":45,"sales":50,"login":55,"items":60,"search":368,"minimal":399,"duo":418,"switchNav":427,"pricingDeployment":438},{"config":41},{"href":42,"dataGaName":43,"dataGaLocation":44},"/","gitlab logo","header",{"text":46,"config":47},"Get free trial",{"href":48,"dataGaName":49,"dataGaLocation":44},"https://gitlab.com/-/trial_registrations/new?glm_source=about.gitlab.com&glm_content=default-saas-trial/","free 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AI Hackathon 2026: Meet the winners","Nearly 7,000 developers built 600+ AI agents and flows on GitLab Duo Agent Platform. Find out who won and what they created.",[720],"Nick Veenhof","https://res.cloudinary.com/about-gitlab-com/image/upload/v1776457632/llddiylsgwuze0u1rjks.png","2026-04-22","AI writes code. That is expected now. But planning, security, compliance, and deployments? Those gaps remain. I have run contributor programs for years. I have never seen a community respond to technology like this.\n\nThat is why we opened [GitLab Duo Agent Platform](https://about.gitlab.com/gitlab-duo-agent-platform/) and invited developers worldwide to build AI agents that help teams ship secure software faster. Not chatbots that answer questions, but agents that jump into workflows, respond to events, and act on your behalf. The GitLab AI Hackathon ran from February 9 to March 25, 2026, on Devpost, the hackathon platform. Google Cloud and Anthropic joined as co-sponsors.\n\nWhen my team planned this hackathon with Google Cloud and Anthropic, I asked the judges to score four things: technical work, design, potential impact, and idea quality. We hoped for strong turnout. What we got surprised all of us. Nineteen judges spent 18 days reviewing every entry. Google Cloud and Anthropic provided judges, prizes, and cloud access. The community built hundreds of agents and flows because they wanted to solve these problems.\n\nNearly 7,000 developers showed up. They built 600+ agents and flows in weeks. The prizes across all categories totaled $65,000 from GitLab, Google Cloud, and Anthropic.\n\n\nIf you have ever watched a senior engineer leave and take half the team's knowledge with them, you know why the winning project hit so hard.\n\nRead on to find out what the community built.\n\n## Grand Prize: LORE\n\n[LORE](https://devpost.com/software/lore-living-organizational-record-engine), the Living Organizational Record Engine, uses eight agents with a router that sends each question to the right agent, logic to prevent circular loops in the knowledge graph, a visual dashboard, and carbon tracking. The command-line tool ships with 43 tests (yes, 43 tests in a hackathon project).\n\nLORE solves a real problem: the knowledge that lives in engineers' heads and walks out the door when they leave. In my experience, a hackathon project with 43 tests is rare. That many tests in a hackathon project tells you something about the team behind it.\n\nJudge April Guo (Anthropic) wrote: \"This feels like a product, not a hackathon project.\"\n\n\n### Google Cloud winners\n\n[Gitdefender](https://devpost.com/software/gitdefender) won the Google Cloud Grand Prize. It works inside code review workflows, finding and fixing security issues. It spots the bug, writes the fix, and opens the code review. No developer needs to step in.\n\n[Aegis](https://devpost.com/software/aegis-2m1oq0) won the Google Cloud Runner Up. It gives AI-powered explanations for every decision it makes, deployed to Google Cloud and ready for production use.\n\n### Anthropic winners\n\n[GraphDev](https://devpost.com/software/graphdev) won the Anthropic Grand Prize. It maps code links and shows how systems change over time. Judge Aboobacker MK (GitLab) noted it was \"in sync with our work on GitLab knowledge graph.\" Judge Ayush Billore (GitLab) wrote: \"Loved the demo and UX, super useful for understanding how the system evolved and what gets impacted by changes.\" You can see the full impact of a change before you make it.\n\n[DocSync](https://devpost.com/software/pipeheal) won the Anthropic Runner Up. It uses three agents: Detector, Writer, and Reviewer. If DocSync is confident in the fix, it opens a code review. If not, it creates an issue for a human to check.\n\n## Category winners\n\n### Most Technically Impressive\n\nDatabase migrations break things. [Time-Traveler](https://devpost.com/software/time-traveler-w3cxp0) creates a safe copy of your production setup, runs the migration against that copy, and reports the result. It runs five agents connected by a bridge, with real Google Cloud deployment, real PostgreSQL migrations, and real data.\n\n### Most Impactful\n\n[RedAgent](https://devpost.com/software/redagent) checks AI-generated security reports, closing the trust gap between AI findings and developer action. If your team uses AI for security scanning, you know this problem. I have seen teams dismiss AI findings because they could not verify them. RedAgent gives teams a way to check AI output before it reaches developers.\n\n### Easiest to Use\n\n[Launch Control](https://devpost.com/software/launch-control-bgp8az) delivers polished UX and solid infrastructure, and scored well on sustainability too.\n\n## The sustainability signal\n\nFive projects won prizes or bonuses for environmental impact. Software delivery has a carbon cost as CI/CD pipelines, but now LLMs also run compute at scale. We created the Green Agent category to challenge developers to measure and reduce that footprint. Stacy Cline and Kim Buncle from GitLab's sustainability team helped judge the Green Agent category. \n\n### Green Agent prize\n\n[GreenPipe](https://devpost.com/software/greenpipe) scans CI/CD pipelines for environmental impact and produces carbon footprint reports. Judges Kim Buncle and Rajesh Agadi (Google) both backed the project.\n\n### Sustainable Design bonus\n\nSustainable Design bonuses were awarded to the projects with exceptional sustainability practices in their design, from model optimization techniques to energy-efficient architecture choices.\n\n* [BugFlow](https://devpost.com/software/bugflow-ai-regression-detective-ci-optimizer) turned one bug report into 10 fixes in 20 minutes. \n* [DELTA Cyber Reasoning](https://devpost.com/software/delta-cyber-reasoning-system) is automated fuzz testing for security. \n* [CarbonLint](https://devpost.com/software/carbonlint) applied code analysis to energy use.\n* [TFGuardian](https://devpost.com/software/tfguardian) features a carbon footprint analyzer, among other agents.\n\nCongratulations on all the Sustainable Design bonus winners! \n\nJudge Jens-Joris Decorte (TechWolf) cited the result: Costs dropped from $556 to $18 per month, a 96% carbon cut (that is a $538 monthly saving with a sustainability label on it).\n\n## Honorable mentions and the long tail\n\nSix projects received honorable mentions:\n\n\n- [SecurityMonkey](https://devpost.com/software/securitymonkey) injects known vulnerabilities into a test branch and scores how well your security scanners catch them.\n- [stregent](https://devpost.com/software/stregent) monitors CI/CD pipelines and lets developers investigate and merge fixes from WhatsApp without opening a laptop.\n- [Compliance Sentinel](https://devpost.com/software/compliance-sentinel-autonomous-devsecops-governance) scores every merge request for compliance risk and blocks the merge if critical violations are detected.\n- [Carbon Tracker](https://devpost.com/software/carbon-tracker-ij25kf) calculates the carbon footprint of each CI/CD pipeline job and posts optimization tips on the merge request.\n- [RepoWarden](https://devpost.com/software/docuguard) is the first Living Specification Engine, an AI system that captures why code was written, not just what it does.\n- [MR Compliance Auditor](https://devpost.com/software/mr-compliance-auditor) collects evidence across merge requests, maps it to SOC 2 controls, and streams compliance scores to a live dashboard.\n\nMy favorite quote from the judging came from Luca Chun Lun Lit (Anthropic), who described stregent's mobile-first approach: \"Being able to essentially code from your phone is a next level in the engineering experience.\"\n\n> Explore the 600+ entries in the [project gallery](https://gitlab.devpost.com/project-gallery).\n\n## What comes next\n\nEvery agent in this hackathon worked within a single project. They still delivered impressive results. Some participants ran a local knowledge graph alongside their agents to surface code relationships and dependencies within the repo. LORE captures project history. Gitdefender finds vulnerabilities. Pairing agents with richer local context is already helping contributors build sharper tools. The next hackathon will build on what contributors are already doing with richer context. Sign up on [contributors.gitlab.com](https://contributors.gitlab.com/) to be the first to know when details drop.\n\n\n## Get started\n\nA special thanks to Lee Tickett (GitLab) and Mattias Michaux (GitLab) for orchestrating the orchestrators and innovators behind this hackathon!\n\nThank you to every developer who submitted. Nearly 7,000 of you showed what GitLab Duo Agent Platform can do when a community decides to build. I am proud of what you built here, and I cannot wait to see what you build next.\n\nBuild your own agent on [GitLab Duo Agent Platform](https://docs.gitlab.com/user/duo_agent_platform/). Browse community-built agents in the [AI Catalog](https://docs.gitlab.com/user/duo_agent_platform/ai_catalog/). You orchestrate. AI accelerates.\n",[725,260],"AI/ML",{"featured":12,"template":13,"slug":727},"gitlab-ai-hackathon-2026-meet-the-winners",{"content":729,"config":737},{"title":730,"description":731,"authors":732,"heroImage":733,"date":734,"category":9,"tags":735,"body":736},"What’s new in Git 2.54.0?","Learn about release contributions, including new repository maintenance, a new command to edit commit history, a replacement for git-sizer(1), and more.",[18],"https://res.cloudinary.com/about-gitlab-com/image/upload/v1776711651/sj7xxyyuimlarswbyft5.png","2026-04-20",[24,23,260],"The Git project recently released [Git 2.54.0](https://lore.kernel.org/git/xmqqa4uxsjrs.fsf@gitster.g/T/#u). Let's look at a few notable highlights from this release, which includes contributions from the Git team at GitLab.\n\n## Pluggable Object Databases\n\nGit already has the ability to store references with either the \"files\" backend or with the [\"reftable\" backend](https://about.gitlab.com/blog/a-beginners-guide-to-the-git-reftable-format/). This is achieved by having proper abstractions in Git that allows us to have different backends.\n\nBut references are just one of the two important types of data that are stored in repositories, with the other being objects. Objects are stored in the object database, and each object database in turn consists of multiple object sources where objects can be read from or written to. Each object source either stores individual objects as so-called \"loose\" objects, or compresses multiple objects into a \"packfile\" in your `.git/objects` directory.\n\nUntil now, however, these sources did not have a proper abstraction boundary, so the storage format for objects is completely hardcoded into Git. But this is finally changing with pluggable object databases! The concept is straightforward and similar to how we did this for references in the past: Instead of having hardcoded code paths for how to store objects, we introduce an abstraction boundary that allows us to have different backends for storing objects.\n\nWhile the idea is simple, the implementation is not, as we have hardcoded assumptions about the storage formats used in Git all over the place. In fact, we have started working on this topic in Git 2.48, which was released in January 2025. Initially, we focused on making object-related subsystems self-contained and creating proper subsystems for the existing backends that we had in Git.\n\nWith Git 2.54, we have now reached a milestone: The object database backend is now pluggable. Not all of Git's functionality is covered yet, but introducing an alternate backend that handles a meaningful subset of operations is now a realistic undertaking.\n\nFor now, only local workflows like creating commits, showing commit graphs, or performing merges will work with such an alternative implementation. This notably excludes anything that interacts with a remote, such as when you want to fetch or push changes. Regardless, this is the culmination of almost two years of work spanning across almost 400 commits that have been merged upstream, and we will of course continue to iterate on this effort.\n\nSo why does this matter? The idea is that it becomes practical to introduce new storage formats into Git. Examples could be:\n- A storage format that is able to store large binary files more efficiently\n  than packfiles do today\n\n- A storage format that is custom-tailored for GitLab to ensure that we can\n  serve repositories to our users even more efficiently than we currently can\n\n\nThis is a large-scale effort that is likely to shape the future of Git and GitLab.\n\n*This project was led by [Patrick Steinhardt](https://gitlab.com/pks-gitlab).*\n\n## Easier editing of your commit history\n\nIn many software development projects it is common practice for developers to not only polish the code they want to contribute, but to also polish the commit history so that it becomes easy to review. The result is a set of small and atomic commits that each do one thing, with a good commit message that describes the intent of the commit as well as specific nuances.\n\nOf course, more often than not, these atomic commits are not something that just happens naturally during the development process. Instead, the author of the changes will gain a better understanding of what they are while iterating on them, and the way to split up the commits will become clearer over time. Furthermore, the subsequent review process may result in feedback that requires changes to the crafted commits.\n\nThe consequence of this process is that the developer will have to rewrite their commit history many times during the development process. Historically, Git has allowed for this use case via [interactive rebases](https://git-scm.com/docs/git-rebase#_interactive_mode). These interactive rebases are an extremely powerful tool: They let you reorder commits, rewrite commit messages, squash multiple commits together, or perform arbitrary edits of any commit.\n\nBut they are also somewhat arcane and hard to understand. The user needs to figure out the base commit for the rebase, they need to understand how to edit a somewhat obscure \"instruction sheet,\" and they need to be aware of how the stateful rebasing process works. For example, users are presented with an instruction sheet similar to the following when rebasing a topic branch:\n\n```shell\npick b60623f382 # t: detect errors outside of test cases # empty\npick b80cb55882 # t: prepare `test_match_signal ()` calls for `set -e`\npick 5ffe397f30 # t: prepare `test_must_fail ()` for `set -e`\npick 5e9b0cf5e1 # t: prepare `stop_git_daemon ()` for `set -e`\npick 299561e7a2 # t: prepare `git config --unset` calls for `set -e`\npick ed0e7ca2b5 # t: detect errors outside of test cases\n```\n\nSo while interactive rebases are powerful, they are also quite intimidating for the average user.\n\nIt doesn't have to be this way, though. Tools like [Jujutsu](https://www.jj-vcs.dev/latest/) provide interfaces that are much easier to use compared to Git, as you can for example simply execute `jj split` to split up a commit into two commits. With Git and interactive rebases, this use case requires a lot of different steps with confusing command line arguments.\n\nWe have thus taken inspiration from Jujutsu and have introduced a new git-history(1) command into Git that is the foundation for better history editing. For now, this command has two subcommands:\n\n- `git history reword` allows you to easily rewrite a commit message. You simply\n  give it the commit whose message you want to reword, Git asks you for the new\n  commit message, and that's it.\n\n- `git history split` allows you to split up a commit into two, which is\n  inspired by `jj split`. You give it a commit, Git asks you which changes to\n  stage into which commit and for the two commit messages, and then you're done.\n\n\nThis is of course only a start, and we want to add additional subcommands over time. For example:\n\n- `git history fixup` to take staged changes and automatically amend them to a\n  specific commit\n\n- `git history drop` to remove a commit\n- `git history reorder` to reorder the sequence of commits\n- `git history squash` to squash a range of commits\n\nBut that's not all! In addition to making history editing easy, this new command also knows to automatically rebase all of your local branches that previously included this commit. So that means that you can even edit a commit that is not on the current branch, and all branches that contain the commit will be rewritten.\n\nIt may seem puzzling at first that Git is automatically rebasing dependent branches, as that is a significant diversion from how git-rebase(1) works. But this is part of a bigger effort to bring better support for Stacked Diffs to Git, which are a way to create a series of multiple dependent branches that can be reviewed independently, but that together work towards a bigger goal.\n\n*This project was led by [Patrick Steinhardt](https://gitlab.com/pks-gitlab) with support from [Elijah Newren](https://github.com/newren).*\n\n## A native replacement for git-sizer(1)\n\nThe size of a Git repository is an important factor that determines how well Git and GitLab can handle it. But size alone is not the only factor, as the performance of a repository is ultimately a combination of multiple different dimensions:\n\n- The depth of the commit history\n- The shape of the directory structure\n- The size of files stored in the repository\n- The number of references\n\nThese are only some of the dimensions one needs to consider when trying to predict whether Git will be able to handle a repository well.\n\nBut while it is clear that the mere repository size is insufficient, Git itself does not provide any tooling that gives the user an easy overview of these metrics. Instead, users are forced to rely on third-party tools like [git-sizer(1)](https://github.com/github/git-sizer) to fill this gap. This tool does an excellent job at surfacing this information, but it is not part of Git itself and thus needs to be installed separately.\n\nObservability of repository internals is critical to us at GitLab, so we introduced a [new `git repo structure` command into Git 2.52](https://about.gitlab.com/blog/whats-new-in-git-2-52-0/#new-subcommand-for-git-repo1-to-display-repository-metrics) to display repository metrics, which we have extended in Git 2.53 to [show inflated and disk sizes for objects by type](https://about.gitlab.com/blog/whats-new-in-git-2-53-0/#more-data-collected-in-git-repo-structure).\n\nIn Git 2.54, we are now iterating some more on this command so that we don't only show the overall size, but also show the largest objects by type:\n\n```shell\n$ git clone https://gitlab.com/git-scm/git.git\n$ cd git\n$ git repo structure\nCounting objects: 410445, done.\n| Repository structure      | Value       |\n| ------------------------- | ----------- |\n| * References              |             |\n|   * Count                 |    1.01 k   |\n|     * Branches            |       1     |\n|     * Tags                |    1.00 k   |\n|     * Remotes             |       9     |\n|     * Others              |       0     |\n|                           |             |\n| * Reachable objects       |             |\n|   * Count                 |  410.45 k   |\n|     * Commits             |   83.99 k   |\n|     * Trees               |  164.46 k   |\n|     * Blobs               |  161.00 k   |\n|     * Tags                |    1.00 k   |\n|   * Inflated size         |    7.46 GiB |\n|     * Commits             |   57.53 MiB |\n|     * Trees               |    2.33 GiB |\n|     * Blobs               |    5.07 GiB |\n|     * Tags                |  737.48 KiB |\n|   * Disk size             |  181.37 MiB |\n|     * Commits             |   33.11 MiB |\n|     * Trees               |   40.58 MiB |\n|     * Blobs               |  107.11 MiB |\n|     * Tags                |  582.67 KiB |\n|                           |             |\n| * Largest objects         |             |\n|   * Commits               |             |\n|     * Maximum size    [1] |   17.23 KiB |\n|     * Maximum parents [2] |      10     |\n|   * Trees                 |             |\n|     * Maximum size    [3] |   58.85 KiB |\n|     * Maximum entries [4] |    1.18 k   |\n|   * Blobs                 |             |\n|     * Maximum size    [5] | 1019.51 KiB |\n|   * Tags                  |             |\n\n|     * Maximum size    [6] |    7.13 KiB |\n\n[1] f6ecb603ff8af608a417d7724727d6bc3a9dbfdf\n[2] 16d7601e176cd53f3c2f02367698d06b85e08879\n[3] 203ee97047731b9fd3ad220faa607b6677861a0d\n[4] 203ee97047731b9fd3ad220faa607b6677861a0d\n[5] aa96f8bc361fd84a1459440f1e7de02ab0dc3543\n[6] 07e38db6a5a03690034d27104401f6c8ea40f1fc\n```\n\nWith this information we're now almost feature-complete as compared to git-sizer(1). We're not done yet, though — we plan to eventually add additional features such as:\n\n- Severity levels as they exist in git-sizer(1)\n- Graphs that show you the distribution of object sizes\n- The ability to scan objects reachable via a subset of references\n\n*This project was led by [Justin Tobler](https://gitlab.com/justintobler).*\n\n## New infrastructure for repository maintenance\n\nWhenever you write data into a Git repository you will typically end up adding more loose objects. Left unmanaged, this leads to a large number of separate files in your `.git/objects/` directory, which slows down several operations that want to access many objects at once. Git thus regularly packs these objects into \"packfiles\" to ensure good performance.\n\nThis isn't the only data structure that may become inefficient over time: Updating references may create loose references, reflogs will need trimming, worktrees may become stale, and caches like commit-graphs need to be refreshed regularly.\n\nAll of these tasks have historically been managed by [git-gc(1)](https://git-scm.com/docs/git-gc). However, this tool has a monolithic architecture, where it basically executes all of the tasks required in sequential order. This foundation is hard to extend and doesn't give the end user much flexibility in case they want to slightly modify how housekeeping is performed.\n\nThe Git project introduced the new [git-maintenance(1)](https://git-scm.com/docs/git-maintenance) tool in Git 2.29. In contrast to git-gc(1), git-maintenance(1) is not monolithic but is instead structured around tasks. These tasks are freely configurable by the user so that the user can control which tasks are running, giving them much more fine-grained control over repository maintenance.\n\nEventually, Git has migrated to use git-maintenance(1) by default. But in the beginning, the only task that was default-enabled was the git-gc(1) task, which as you might have guessed, simply executes `git gc`. To manually run maintenance using this new command you can execute `git maintenance run`, but Git knows to execute this automatically after several other commands.\n\nOver the last couple releases we have implemented all the individual tasks that are supported by git-gc(1) in git-maintenance(1) to ensure that we have feature parity between these two tools.\n\nFurthermore, we have implemented a new task that uses Git's modern architecture for repacking objects with [geometric compaction](https://git-scm.com/docs/git-repack#Documentation/git-repack.txt---geometricfactor).\nGeometric compaction is a much better fit for large monorepos, and with our efforts to make them work well with partial clones [that landed in Git 2.53](https://about.gitlab.com/blog/whats-new-in-git-2-53-0/#geometric-repacking-support-with-promisor-remotes) they are now a full replacement for our previous repacking strategy in Git.\n\nIn Git 2.54, we have now reached another significant milestone: Instead of using the git-gc(1)-based strategy by default, we are now using geometric repacking with fine-grained individual maintenance tasks! Besides being more efficient for large monorepos, it also ensures that we have an easier foundation to iterate on going forward.\n\n*The git-maintenance(1) infrastructure was originally implemented by [Derrick Stolee](https://github.com/derrickstolee) and geometric maintenance was introduced by [Taylor Blau](https://github.com/ttaylorr). The effort to introduce the new fine-grained tasks and migrate to the new maintenance strategy was led by [Patrick Steinhardt](https://gitlab.com/pks-gitlab).*\n\n## Read more\n\nThis article highlighted just a few of the contributions made by GitLab and the wider Git community for this latest release. You can learn about these from the [official release announcement](https://lore.kernel.org/git/xmqqa4uxsjrs.fsf@gitster.g/T/#u) of the Git project. Also, check out our [previous Git release blog posts](https://about.gitlab.com/blog/tags/git/) to see other past highlights of contributions from GitLab team members.",{"slug":738,"featured":12,"template":13},"whats-new-in-git-2-54-0",{"content":740,"config":749},{"title":741,"description":742,"authors":743,"date":745,"body":746,"heroImage":747,"category":9,"tags":748},"What’s new in Git 2.53.0?","Learn about release contributions, including fixes for geometric repacking, updates to git-fast-import(1) commit signature handing options, and more.",[744],"Justin Tobler","2026-02-02","The Git project recently released [Git 2.53.0](https://lore.kernel.org/git/xmqq4inz13e3.fsf@gitster.g/T/#u). Let's look at a few notable highlights from this release, which includes\ncontributions from the Git team at GitLab.\n\n## Geometric repacking support with promisor remotes\n\nNewly written objects in a Git repository are often stored as individual loose files. To ensure good performance and optimal use of disk space, these loose objects are regularly compressed into so-called packfiles. The number of packfiles in a repository grows over time as a result of the user’s activities, like writing new commits or fetching from a remote. As the number of packfiles in a repository increases, Git has to do more work to look up individual objects. Therefore, to preserve optimal repository performance, packfiles are periodically repacked via git-repack(1) to consolidate the objects into fewer packfiles. When repacking there are two strategies: “all-into-one” and “geometric”.\n\nThe all-into-one strategy is fairly straightforward and the current default. As its name implies, all objects in the repository are packed into a single packfile. From a performance perspective this is great for the repository as Git only has to scan through a single packfile when looking up objects. The main downside of such a repacking strategy is that computing a single packfile for a repository can take a significant amount of time for large repositories.\n\nThe geometric strategy helps mitigate this concern by maintaining a geometric progression of packfiles based on their size instead of always repacking into a single packfile. To explain more plainly, when repacking Git maintains a set of packfiles ordered by size where each packfile in the sequence is expected to be at least twice the size of the preceding packfile. If a packfile in the sequence violates this property, packfiles are combined as needed until the progression is restored. This strategy has the advantage of still minimizing the number of packfiles in a repository while also minimizing the amount of work that must be done for most repacking operations.\n\nOne problem with the geometric repacking strategy was that it was not compatible with partial clones. Partial clones allow the user to clone only parts of a repository by, for example, skipping all blobs larger than 1 megabyte. This can significantly reduce the size of a repository, and Git knows how to backfill missing objects that it needs to access at a later point in time.\n\nThe result is a repository that is missing some objects, and any object that may not be fully connected is stored in a “promisor” packfile.  When repacking, this promisor property needs to be retained going forward for packfiles containing a promisor object so it is known whether a missing object is expected and can be backfilled from the promisor remote. With an all-into-one repack, Git knows how to handle promisor objects properly and stores them in a separate promisor packfile. Unfortunately, the geometric repacking strategy did not know to give special treatment to promisor packfiles and instead would merge them with normal packfiles without considering whether they reference promisor objects. Luckily, due to a bug the underlying git-pack-objects(1) dies when using geometric repacking in a partial clone repository. So this means repositories in this configuration were not able to be repacked anyways which isn’t great, but better than repository corruption.\n\nWith the release of Git 2.53, geometric repacking now works with partial clone repositories. When performing a geometric repack, promisor packfiles are handled separately in order to preserve the promisor marker and repacked following a separate geometric progression. With this fix, the geometric strategy moves closer towards becoming the default repacking strategy. For more information check out the corresponding [mailing list thread](https://lore.kernel.org/git/20260105-pks-geometric-repack-with-promisors-v1-0-c4660573437e@pks.im/).\n\nThis project was led by [Patrick Steinhardt](https://gitlab.com/pks-gitlab).\n\n## git-fast-import(1) learned to preserve only valid signatures\n\nIn our [Git 2.52 release article](https://about.gitlab.com/blog/whats-new-in-git-2-52-0/), we covered signature related improvements to git-fast-import(1) and git-fast-export(1). Be sure to check out that post for a more detailed explanation of these commands, how they are used, and the changes being made with regards to signatures.\n\nTo quickly recap, git-fast-import(1) provides a backend to efficiently import data into a repository and is used by tools such as [git-filter-repo(1)](https://github.com/newren/git-filter-repo) to help rewrite the history of a repository in bulk. In the Git 2.52 release, git-fast-import(1) learned the `--signed-commits=\u003Cmode>` option similar to the same option in git-fast-export(1). With this option, it became possible to unconditionally retain or strip signatures from commits/tags.\n\nIn situations where only part of the repository history has been rewritten, any signature for rewritten commits/tags becomes invalid. This means git-fast-import(1) is limited to either stripping all signatures or keeping all signatures even if they have become invalid. But retaining invalid signatures doesn’t make much sense, so rewriting history with git-repo-filter(1) results in all signatures being stripped, even if the underlying commit/tag is not rewritten. This is unfortunate because if the commit/tag is unchanged, its signature is still valid and thus there is no real reason to strip it. What is really needed is a means to preserve signatures for unchanged objects, but strip invalid ones.\n\nWith the release of Git 2.53, the git-fast-import(1) `--signed-commits=\u003Cmode>` option has learned a new `strip-if-invalid` mode which, when specified, only strips signatures from commits that become invalid due to being rewritten. Thus, with this option it becomes possible to preserve some commit signatures when using git-fast-import(1). This is a critical step towards providing the foundation for tools like git-repo-filter(1) to preserve valid signatures and eventually re-sign invalid signatures.\n\nThis project was led by [Christian Couder](https://gitlab.com/chriscool).\n\n## More data collected in git-repo-structure\n\nIn the Git 2.52 release, the “structure” subcommand was introduced to git-repo(1). The intent of this command was to collect information about the repository and eventually become a native replacement for tools such as [git-sizer(1)](https://github.com/github/git-sizer). At GitLab, we host some extremely large repositories, and having insight into the general structure of a repository is critical to understand its performance characteristics. In this release, the command now also collects total size information for reachable objects in a repository to help understand the overall size of the repository. In the output below, you can see the command now collects both the total inflated and disk sizes of reachable objects by object type.\n\n```shell\n$ git repo structure\n\n| Repository structure | Value      |\n| -------------------- | ---------- |\n| * References         |            |\n|   * Count            |   1.78 k   |\n|     * Branches       |      5     |\n|     * Tags           |   1.03 k   |\n|     * Remotes        |    749     |\n|     * Others         |      0     |\n|                      |            |\n| * Reachable objects  |            |\n|   * Count            | 421.37 k   |\n|     * Commits        |  88.03 k   |\n|     * Trees          | 169.95 k   |\n|     * Blobs          | 162.40 k   |\n|     * Tags           |    994     |\n|   * Inflated size    |   7.61 GiB |\n|     * Commits        |  60.95 MiB |\n|     * Trees          |   2.44 GiB |\n|     * Blobs          |   5.11 GiB |\n|     * Tags           | 731.73 KiB |\n|   * Disk size        | 301.50 MiB |\n|     * Commits        |  33.57 MiB |\n|     * Trees          |  77.92 MiB |\n|     * Blobs          | 189.44 MiB |\n|     * Tags           | 578.13 KiB |\n```\n\nThe keen-eyed among you may have also noticed that the size values in the table output are also now listed in a more human-friendly manner with units appended. In subsequent releases we hope to further expand this command's output to provide additional data points such as the largest individual objects in the repository.\n\nThis project was led by [Justin Tobler](https://gitlab.com/justintobler).\n\n## Read more\n\nThis article highlighted just a few of the contributions made by GitLab and\nthe wider Git community for this latest release. You can learn about these from\nthe [official release announcement](https://lore.kernel.org/git/xmqq4inz13e3.fsf@gitster.g/T/#u) of the Git project. Also, check\nout our [previous Git release blog posts](https://about.gitlab.com/blog/tags/git/)\nto see other past highlights of contributions from GitLab team members.","https://res.cloudinary.com/about-gitlab-com/image/upload/v1749663087/Blog/Hero%20Images/git3-cover.png",[24,23,260],{"featured":28,"template":13,"slug":750},"whats-new-in-git-2-53-0",{"promotions":752},[753,767,779,791],{"id":754,"categories":755,"header":757,"text":758,"button":759,"image":764},"ai-modernization",[756],"ai-ml","Is AI achieving its promise at scale?","Quiz will take 5 minutes or less",{"text":760,"config":761},"Get your AI maturity score",{"href":762,"dataGaName":763,"dataGaLocation":242},"/assessments/ai-modernization-assessment/","modernization assessment",{"config":765},{"src":766},"https://res.cloudinary.com/about-gitlab-com/image/upload/v1772138786/qix0m7kwnd8x2fh1zq49.png",{"id":768,"categories":769,"header":771,"text":758,"button":772,"image":776},"devops-modernization",[770,568],"product","Are you just managing tools or shipping innovation?",{"text":773,"config":774},"Get your DevOps maturity score",{"href":775,"dataGaName":763,"dataGaLocation":242},"/assessments/devops-modernization-assessment/",{"config":777},{"src":778},"https://res.cloudinary.com/about-gitlab-com/image/upload/v1772138785/eg818fmakweyuznttgid.png",{"id":780,"categories":781,"header":783,"text":758,"button":784,"image":788},"security-modernization",[782],"security","Are you trading speed for security?",{"text":785,"config":786},"Get your security maturity score",{"href":787,"dataGaName":763,"dataGaLocation":242},"/assessments/security-modernization-assessment/",{"config":789},{"src":790},"https://res.cloudinary.com/about-gitlab-com/image/upload/v1772138786/p4pbqd9nnjejg5ds6mdk.png",{"id":792,"paths":793,"header":796,"text":797,"button":798,"image":803},"github-azure-migration",[794,795],"migration-from-azure-devops-to-gitlab","integrating-azure-devops-scm-and-gitlab","Is your team ready for GitHub's Azure move?","GitHub is already rebuilding around Azure. Find out what it means for you.",{"text":799,"config":800},"See how GitLab compares to GitHub",{"href":801,"dataGaName":802,"dataGaLocation":242},"/compare/gitlab-vs-github/github-azure-migration/","github azure migration",{"config":804},{"src":778},{"header":806,"blurb":807,"button":808,"secondaryButton":813},"Start building faster today","See what your team can do with the intelligent orchestration platform for DevSecOps.\n",{"text":809,"config":810},"Get your free trial",{"href":811,"dataGaName":49,"dataGaLocation":812},"https://gitlab.com/-/trial_registrations/new?glm_content=default-saas-trial&glm_source=about.gitlab.com/","feature",{"text":504,"config":814},{"href":53,"dataGaName":54,"dataGaLocation":812},1777317545080]