Pacdiff -s Bug - merge

And meld only provides you a GUI comparison of the 2 files. It cannot automatically merge.
In your latest example of an issue it would never even get to DIFFPROG.
Because

Which is from

Which would have been generated by

base_cache_tar() {
        package="$1"

        for cachedir in "${cachedirs[@]}"; do
                pushd "$cachedir" &>/dev/null || {
                        error "failed to chdir to '%s', skipping" "$cachedir"
                        continue
                }

                find "$PWD" -name "$package-[0-9]*.pkg.tar*" ! -name '*.sig' |
                        pacsort --files --reverse | sed -ne '2p'

                popd &>/dev/null || exit
        done
}
        package="$(pacman -Qoq "$file")" || return 1
        base_tar="$(base_cache_tar "$package")"

Which would not affect certain other operations (like v).
But this methodology was changed with the commit

For example what was

	[[ -d $cachedir ]] ||
		die "cachedir '%s' does not exist or is not a directory" "$cachedir"

	# unlikely that this will fail, but better make sure
	pushd "$cachedir" &>/dev/null || die "failed to chdir to '%s'" "$cachedir"

Became

	for cachedir in "${cachedirs[@]}"; do
		pushd "$cachedir" &>/dev/null || {
			error "failed to chdir to '%s', skipping" "$cachedir"
			continue
		}

And this happened at Arch about a year ago.
So you might have seen it in Manjaro sometime between then and now.

Seems likely maybe?