cp-merge-directories-by-hardlinks

#!/bin/bash

# Merge two directories on the same disk recursively by using hard links
# and avoiding to copy a file

source bash-helpers

src=${1?specify source directory}
dst=${2?specify destination base directory}

if [[ $dst = . ]] ; then
    dst=$(basename $(abs $src))
fi

src_base=$(basename "$src")
dst="$dst/$src_base"

INFO "copying $src -> $dst"

mkdir -p "$dst"

test -d "$src" || DIE "Not a directory: $src"
test -d "$dst" || DIE "Not a directory: $dst"

src_device=$(stat --format "%d" "$src")
dst_device=$(stat --format "%d" "$dst")
if [[ $src_device != $dst_device ]] ; then
    DIE "$src and $dst have to reside on the same device for hard links to work"
fi

cp -rnl "$src"/* "$dst"/