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fetch, clone: add fetch.blobSizeLimit config#2058

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abraithwaite wants to merge 1 commit intogitgitgadget:masterfrom
abraithwaite:alan/fetch-blob-size-limit
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fetch, clone: add fetch.blobSizeLimit config#2058
abraithwaite wants to merge 1 commit intogitgitgadget:masterfrom
abraithwaite:alan/fetch-blob-size-limit

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@abraithwaite abraithwaite commented Feb 28, 2026

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@abraithwaite abraithwaite force-pushed the alan/fetch-blob-size-limit branch 7 times, most recently from 525eef2 to 8d656a9 Compare March 1, 2026 06:05
External tools like git-lfs and git-fat use the filter clean/smudge
mechanism to manage large binary objects, but this requires pointer
files, a separate storage backend, and careful coordination. Git's
partial clone infrastructure provides a more native approach: large
blobs can be excluded at the protocol level during fetch and lazily
retrieved on demand. However, enabling this requires passing
`--filter=blob:limit=<size>` on every clone, which is not
discoverable and cannot be set as a global default.

Add a new `fetch.blobSizeLimit` configuration option that enables
size-based partial clone behavior globally. When set, both `git
clone` and `git fetch` automatically apply a `blob:limit=<size>`
filter. Blobs larger than the threshold that are not needed for the
current worktree are excluded from the transfer and lazily fetched
on demand when needed (e.g., during checkout, diff, or merge).

This makes it easy to work with repositories that have accumulated
large binary files in their history, without downloading all of
them upfront.

The precedence order is:
  1. Explicit `--filter=` on the command line (highest)
  2. Existing `remote.<name>.partialclonefilter`
  3. `fetch.blobSizeLimit` (new, lowest)

Once a clone or fetch applies this setting, the remote is registered
as a promisor remote with the corresponding filter spec, so
subsequent fetches inherit it automatically. If the server does not
support object filtering, the setting is silently ignored.

Signed-off-by: Alan Braithwaite <alan@braithwaite.dev>
@abraithwaite abraithwaite force-pushed the alan/fetch-blob-size-limit branch from 8d656a9 to 818b64e Compare March 1, 2026 06:09
@Ikke
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Ikke commented Mar 1, 2026

/allow

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User abraithwaite is now allowed to use GitGitGadget.

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@abraithwaite
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/submit

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gitgitgadget bot commented Mar 1, 2026

Submitted as pull.2058.git.1772383499900.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-2058/abraithwaite/alan/fetch-blob-size-limit-v1

To fetch this version to local tag pr-2058/abraithwaite/alan/fetch-blob-size-limit-v1:

git fetch --no-tags https://github.com/gitgitgadget/git/ tag pr-2058/abraithwaite/alan/fetch-blob-size-limit-v1

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