nix/doc/manual/rl-next/shallow-git-fetching-by-default.md

synopsis	prs
`fetchTree` now fetches git repositories shallowly by default	10028

builtins.fetchTree now clones git repositories shallowly by default, which reduces network traffic and disk usage significantly in many cases.

Previously, the default behavior was to clone the full history of a specific tag or branch (eg. ref) and only afterwards extract the files of one specific revision.

From now on, the ref and allRefs arguments will be ignored, except if shallow cloning is disabled by setting shallow = false.

The defaults for builtins.fetchGit remain unchanged. Here, shallow cloning has to be enabled manually by passing shallow = true.