Git 2.55 — big speedups for large repositories (Linuxiac)

A Linuxiac writeup of the Git 2.55 release (June 29, 2026), whose theme is making large repositories faster — the practical face of the spoke’s monorepo-scaling thread. T4: independent trade tech-news, not the primary; the facts trace to Git’s own release notes (the T1 upgrade path if a future ingest wants it), but the report is technically specific and consistent.

Performance — the headline

• Linux FSMonitor (inotify). Brings filesystem monitoring to Linux, so git status queries change events instead of scanning the whole working tree — the big-repo win. One inotify watch per directory, so very large trees may need a higher fs.inotify.max_user_watches; network-mounted repos stay opt-in.
• Faster reachability bitmaps. Object-reachability generation during repack dropped from ~612s to ~294s in one benchmark (~2×).
• Incremental multi-pack indexing. New git repack --write-midx=incremental builds MIDX in incremental chains, cutting repack cost on large projects (incremental, not full-rebuild — the same “don’t redo the whole thing” instinct as the rest of the release).
• Path-walk with filters. git pack-objects --path-walk now works with blob:none / blob:limit / tree:0 filters, improving partial-clone workflows.

New features

• git history fixup <commit> (experimental) — applies staged changes to an earlier commit and replays the commits after it.
• Parallel configured hooks — independent pre-commit checks (linting, unit tests) run concurrently when marked safe.
• Remote-group pushing — publish branches to several remotes at once.
• Graph limiting — git log --graph --graph-lane-limit=<n> constrains history width.
• Oldest-commit selection — git rev-list --max-count-oldest=<n>.

Why it matters here

It anchors the incumbent VCS (git) the spoke’s version-control corner was missing, and lands squarely on the large-repo scaling problem: nearly every headline (FSMonitor, incremental MIDX, bitmap repack, partial-clone path-walk) is about keeping one big repository fast — the cost Block’s monorepo had to build tooling around, here addressed inside Git itself.

Related

git · monorepo · lore · block-monorepo-migration · developer-tooling