More generic version of https://gist.github.com/cketti/724c5cd15ff69517540fe0aba7f7dc56

generate_android_sources.sh

#!/usr/bin/env bash

set -euo pipefail

##########
# Config #
##########

readonly GIT_BRANCH='android-8.0.0_r4'
readonly API_LEVEL='26'

###########
# Helpers #
###########

readonly CUR_DIR=$( pwd )
readonly WORKING_DIR=$( mktemp -d )

setup() {
  pushd ${WORKING_DIR}
  mkdir -p frameworks/base
}

teardown() {
  popd
  rm -rf "${WORKING_DIR}"
}

fetch_sources() {
  local -r target_branch="${1}"

  # Fetch repositories that contain the sources we're interested in
  git clone --depth 1 https://android.googlesource.com/platform/frameworks/base -b "${target_branch}" frameworks/base
  git clone --depth 1 https://android.googlesource.com/platform/libcore -b "${target_branch}"
  git clone --depth 1 https://android.googlesource.com/platform/development -b  "${target_branch}"
}

package_sources() {
  local -r zip_name="${1}"

  # Create a basic source.properties file
  echo -e "Pkg.UserSrc=false\nPkg.Revision=1\nAndroidVersion.ApiLevel=${API_LEVEL}" > source.properties

  # Modify the script to create a sources ZIP to use "android-26" as top-level directory
  cat development/build/tools/mk_sources_zip.py | sed -e "s/TOP_FOLDER = .*/TOP_FOLDER = \"android-${API_LEVEL}\"/" > my_mk_sources_zip.py

  # Run the script to create android-26-sources.zip
  python my_mk_sources_zip.py -z source.properties "${zip_name}" .
}

maybe_install_sources() {
  local -r zip_name="${1}"

  local -r sources_dir="${ANDROID_HOME}/sources"
  local -r target_path="${sources_dir}/android-${API_LEVEL}"

  if [ -d "${target_path}" ]; then
    echo ""
    echo "WARN: directory exists [${target_path}] copying instead..."

    local -r zip_path="${CUR_DIR}/${zip_name}"
    if [ -f "${zip_path}" ]; then
      echo "WARN: nevermind, file exists [${zip_path}] skipping..."
    else
      cp "${zip_name}" "${CUR_DIR}/"
    fi
  else
    unzip "${zip_name}" -d "${sources_dir}"
  fi
}

###############
# DO WORK SON #
###############

main() {
  local -r zip_name="android-${API_LEVEL}-sources.zip"

  setup

  fetch_sources "${GIT_BRANCH}"
  package_sources "${zip_name}"
  maybe_install_sources "${zip_name}"

  teardown
}

main

I had to change the first line to #!/usr/bin/env bash (set -o pipefail is bash-specific). Also: love it, thanks a lot!