Commit c59a777a authored by Valentin Gagarin's avatar Valentin Gagarin
Browse files

nix-prefetch-git: add `--name` parameter 

This allows tools like `npins` to avoid re-downloading pre-fetched sources at evaluation time,
by setting the same symbolic store path name as `builtins.fetchGit` does,
and would make hacks such as [0] obsolete.

Historical note: `builtins.fetchGit` was introduced in 2016 [1] and
released in 2018 [2]. Before that, there was only the Nixpkgs `fetchgit`,
and the convention for using constant store path names [3] was not established yet [4].

While arguably in retrospect store path names were a mistake, we cannot
undo it here even partially by setting them to a constant, as it would invalidate
countless fixed-output derivations and thus incur an increase in
resource consumption and potentially a large number of build failures.

[0]: https://github.com/andir/npins/commit/f0449d090cd4cbf17849d29821a53ead9a88c42a
[1]: https://github.com/nixos/nix/commit/38539b943a060d9cdfc24d6e5d997c0885b8aa2f
[2]: https://github.com/NixOS/nix/releases/tag/2.0
[3]: https://github.com/NixOS/nix.dev/blob/db00265e810b3729a1077a0e5f8f4112f49019af/source/guides/best-practices.md#L263-L264
[4]: https://github.com/NixOS/nixpkgs/commit/a8603605aaaf780aa45edd0f16c8c9588455ccf2
parent 6b691c15

pkgs/build-support/fetchgit/builder.sh

+1 −1
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ 


echo "exporting $url (rev $rev) into $out"



$SHELL $fetcher --builder --url "$url" --out "$out" --rev "$rev" \

$SHELL $fetcher --builder --url "$url" --out "$out" --rev "$rev" --name "$name" \

  ${leaveDotGit:+--leave-dotGit} \

  ${fetchLFS:+--fetch-lfs} \

  ${deepClone:+--deepClone} \

pkgs/build-support/fetchgit/nix-prefetch-git

+10 −2
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ Options: 
      --url url       Any url understood by 'git clone'.

      --rev ref       Any sha1 or references (such as refs/heads/master)

      --hash h        Expected hash.

      --name n        Symbolic store path name to use for the result (default: based on URL)

      --branch-name   Branch name to check out into

      --sparse-checkout Only fetch and checkout part of the repository.

      --non-cone-mode Use non-cone mode for sparse checkouts.
@@ -75,6 +76,7 @@ for arg; do 
            --url) argfun=set_url;;

            --rev) argfun=set_rev;;

            --hash) argfun=set_hashType;;

            --name) argfun=set_symbolicName;;

            --branch-name) argfun=set_branchName;;

            --deepClone) deepClone=true;;

            --sparse-checkout) argfun=set_sparseCheckout;;
@@ -424,6 +426,12 @@ if test -z "$branchName"; then 
    branchName=fetchgit

fi



if [ -v symbolicName ]; then

    storePathName="$symbolicName"

else

    storePathName="$(url_to_name "$url" "$rev")"

fi



tmpHomePath="$(mktemp -d "${TMPDIR:-/tmp}/nix-prefetch-git-tmp-home-XXXXXXXXXX")"

exit_handlers+=(remove_tmpHomePath)

ln -s "${NETRC:-$HOME/.netrc}" "$tmpHomePath/.netrc"
@@ -443,7 +451,7 @@ else 
    # If the hash was given, a file with that hash may already be in the

    # store.

    if test -n "$expHash"; then

        finalPath=$(nix-store --print-fixed-path --recursive "$hashType" "$expHash" "$(url_to_name "$url" "$rev")")

        finalPath=$(nix-store --print-fixed-path --recursive "$hashType" "$expHash" "$storePathName")

        if ! nix-store --check-validity "$finalPath" 2> /dev/null; then

            finalPath=

        fi
@@ -458,7 +466,7 @@ else 
        tmpPath="$(realpath "$(mktemp -d --tmpdir git-checkout-tmp-XXXXXXXX)")"

        exit_handlers+=(remove_tmpPath)



        tmpFile="$tmpPath/$(url_to_name "$url" "$rev")"

        tmpFile="$tmpPath/$storePathName"

        mkdir -p "$tmpFile"



        # Perform the checkout.