Avoid unnecessary Git refetches #14633
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We don't care if the user (or more likely the lock file) specifies an incorrect value for revCount, since it doesn't matter for security (unlikely content hashes like narHash).
Same as revCount.
builtins.fetchTree was setting `shallow = true` when fetching from git. That's bad because it makes it behave inconsistently from non-fetchTree fetches, e.g. when updating an input. Instead, the Git fetcher now will do a shallow fetch automatically if `revCount` is already set (e.g. when fetching a lock). Fixes #14588.
This fixes the issue where updating a Git input does a non-shallow fetch, and then a subsequent eval does a shallow refetch because the revCount is already known. Now the subsequent eval will use the repo used in the first fetch.
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This was referenced Nov 24, 2025
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Motivation
This fixes the issue where updating a Git input does a non-shallow fetch, and then a subsequent eval does a shallow refetch because the revCount is already known. Now the subsequent eval will use the repo used in the first fetch.
It also gets rid of a hack in
fetchTreethat setsshallow = false, which is bad because it's inconsistent with other fetches. Fixes #14588.Depends on #14596.
Context
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