Errors with recursive cp with S3Paths

[ericphanson]

If src has nested directories and the dst is an S3Path, we get errors since we are missing final /s when we readdir a local directory and get the names.

We could modify cp to insert /s as needed:

function Base.cp(src::AbstractPath, dst::AbstractPath; force=false, follow_symlinks=false)
    if exists(dst)
        if force
            rm(dst; force=force, recursive=true)
        else
            throw(ArgumentError("Destination already exists: $dst"))
        end
    end

    if !exists(src)
        throw(ArgumentError("Source path does not exist: $src"))
    elseif isdir(src)
        mkdir(dst)

        for fp in readdir(src)
            src_fp = src / fp
            dst_fp = dst / fp
            if isdir(src_fp) && !endswith(dst_fp, "/")
                dst_fp *= "/"
            end
            cp(src_fp, dst_fp; force=force)
        end
    elseif isfile(src)
        write(dst, read(src))
    elseif islink(src)
        follow_symlinks ? symlink(readlink(src), dst) : write(dst, read(FilePathsBase.canonicalize(src)))
    else
        throw(ArgumentError("Source path is not a file or directory: $src"))
    end

    return dst
end

Transferred from rofinn/FilePathsBase.jl#128