[RFC] How to pass Git config command line instructions to Submodule commands?

Hi,

a few folks from the Git LFS project and I try to make cloning of repositories with a lot of LFS files faster.

The core problem is that Git LFS uses a Git smudge filter to replace LFS pointers with the actual file content. Right now, a smudge filter can only be executed on an individual file which makes the operation slow for many files [1].

We solved this issue by temporarily disabling the smudge filter for the clone command via Git config (optimized in 1a8630 [2]):

    git -c filter.lfs.smudge= -c filter.lfs.required=false clone <url> <path>

Afterwards Git LFS runs a special command to download and replace all LFS content in bulk [3]. This works great for LFS repositories.

However, I noticed that git config command line instructions such as "-c filter.lfs.smudge=" are not passed to Git submodule operations. Thus this does not work as expected:

    git -c filter.lfs.smudge= -c filter.lfs.required=false clone --recursive <url> <path>

I tried to work around that by copying the relevant pieced from the Git Submodule command [4] and applying the command line Git config manually (look closely at the modified checkout command):

    git -c filter.lfs.smudge= -c filter.lfs.required=false clone $@
    if [[ -z $2 ]]; then
        CLONE_PATH=$(basename ${1%.git});
    else
        CLONE_PATH=$2;
    fi
    pushd "$CLONE_PATH"
        git submodule init
        wt_prefix=$(git rev-parse --show-prefix)
        git submodule--helper list --prefix "$wt_prefix" | {
            while read mode sha1 stage sm_path
            do
                name=$(git submodule--helper name "$sm_path") || exit
                url=$(git config submodule."$name".url)
                if ! test -d "$sm_path"/.git && ! test -f "$sm_path"/.git
                then
                    git submodule--helper clone --prefix "$wt_prefix" --path "$sm_path" --name "$name" --url "$url"
                    pushd "$sm_path"
                        git -c filter.lfs.smudge= -c filter.lfs.required=false checkout -q $sha1 || exit
                        git-lfs pull || exit
                    popd
                fi
            done
        }
    popd

Do you see an easier way to pass command line Git config instructions to the underlaying Git Submodule commands? If not, do you think a patch adding this would be worth working on?

I also started a discussion about that on the Git LFS issue page [5].

Thanks, Lars

[1] https://github.com/github/git-lfs/issues/931 [2] https://github.com/git/git/commit/1a8630dc3b1cc6f1361a4e5d94630133c24c97d9 [3] https://developer.atlassian.com/blog/2016/04/git-lfs-12-clone-faster/ [4] https://github.com/git/git/blob/6a6636270fbaf74609cd3e1bd207dd2c420d640a/git-submodule.sh#L686-L731 [5] https://github.com/github/git-lfs/issues/1172