See,

$ find . -name "*.sh" | xargs shellcheck -i SC2006

In ./roll-tarballs.sh line 62:
    echo "HEAD (on branch `git rev-parse --abbrev-ref HEAD`)"
                          ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean:
    echo "HEAD (on branch $(git rev-parse --abbrev-ref HEAD))"

In ./nx-X11/x-indent-all.sh line 2:
where=`dirname $0`
      ^----------^ SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean:
where=$(dirname $0)

In ./nx-X11/x-indent.sh line 5:
INDENT=`which gnuindent || which gindent || which indent`
       ^-- SC2006: Use $(...) notation instead of legacy backticked `...`.

Did you mean:
INDENT=$(which gnuindent || which gindent || which indent)

For more information:
  https://www.shellcheck.net/wiki/SC2006 -- Use $(...) notation instead of le...
Signed-off-by: Mario Trangoni <mjtrangoni@gmail.com>