resign.sh

#!/bin/bash
set -e
set -x

if [[ -z "$MACOS_CODESIGN_IDENTITY" ]]; then
    echo "ERROR: Must export MACOS_CODESIGN_IDENTITY" > &2
    exit 1
fi

# detach anything that's old
hdiutil detach /Volumes/Julia-* || true

# Mount target dmg, storing modifications in shadow file; find all disk names:
DISKS="$(hdiutil attach -owners on "$1"  -fs HFS+ -shadow | awk '{ print $1 }' | grep -E '/dev/disk\d+$' | sort | uniq)"

# Codesign the app
codesign -s "$MACOS_CODESIGN_IDENTITY" --deep -v /Volumes/Julia*/Julia*.app

# Create "new" DMG from mounted disk
hdiutil create "${1%.*}-new.dmg" -size 1t -fs HFS+ -ov -volname "Julia" -imagekey zlib-level=9 -srcfolder /Volumes/Julia*/

# Unmount the disks
for DISK in ${DISKS}; do
    hdiutil detach "${DISK}" || true
done

# cleanup
mv "${1%.*}-new.dmg" "$1"
rm -f "$1.shadow"