Tvheadend

I understand how to build TVHeadend using commands such as these from a cloned tvheadend directory:

./configure --enable-hdhomerun_client --disable-hdhomerun_static --disable-dvbscan --enable-libav
make -j$(nproc)
make install

I understand that the Autobuild.sh script is used to make an installer .deb file... but when I run it it also builds tvheadend so it must be calling the make command somewhere.

You can call it like this...

AUTOBUILD_CONFIGURE_EXTRA="--enable-hdhomerun_client --disable-hdhomerun_static --disable-dvbscan --enable-libav" ./Autobuild.sh

But I cannot understand exactly how Autobuild.sh works. Can anyone explain it?
This is the Autobuild.sh script...

#!/bin/bash
#
# Entry point for the Doozer autobuild system
#
# (c) Andreas Öman 2011. All rights reserved.
#
#

set -eu

BUILD_API_VERSION=3
EXTRA_BUILD_NAME="" 
JARGS="" 
JOBSARGS="" 
TARGET="debian" 
RELEASE="--release" 
WORKINGDIR="/var/tmp/showtime-autobuild" 
FILELIST="$PWD/filelist.txt" 
OP="build" 
while getopts "vht:e:j:w:o:c:" OPTION
do
  case $OPTION in
      v)
      echo $BUILD_API_VERSION
      exit 0
      ;;
      h)
      echo "This script is intended to be used by the autobuild system only" 
      exit 0
      ;;
      t)
      TARGET="$OPTARG" 
      ;;
      e)
      EXTRA_BUILD_NAME="$OPTARG" 
      ;;
      j)
      JOBSARGS="--jobs=$OPTARG" 
      JARGS="-j$OPTARG" 
      ;;
      w)
      WORKINGDIR="$OPTARG" 
      ;;
      o)
      OP="$OPTARG" 
      ;;
  esac
done

if [[ -z $TARGET ]]; then
    echo "target (-t) not specified" 
    exit 1
fi

#
# $1 = local file path
# $2 = type
# $3 = content-type
# $4 = filename
#
artifact() {
    echo "doozer-artifact:$PWD/$1:$2:$3:$4" 
    echo "$PWD/$1" >> "$FILELIST" 
}

versioned_artifact() {
    echo "doozer-versioned-artifact:$PWD/$1:$2:$3:$4" 
    echo "$PWD/$1" >> "$FILELIST" 
}

git status

if [ -f Autobuild/${TARGET}.sh ]; then
    source Autobuild/${TARGET}.sh
else
    echo "target $TARGET not supported" 
    exit 1
fi

What calls artifact() and versioned_artifact() ?
On my system I would expect this line to get called...
source Autobuild/debian.sh

This is deban.sh

CHANGELOG=debian/changelog
NOW=`date -R`
VER=`$(dirname $0)/support/version`
[ -z "${DEBDIST:-}" ] && DEBDIST="" 

BUILD_DEPS=`awk '\
BEGIN {cnt = 1;}
/^Build-Depends:/ {
  split($0, line, ":");
  split(line[2], deps, ",");
  for (i in deps) {
    d = deps[i];
    sub(/^ */, "", d);
    sub(/ *$/, "", d);
    n = split(d, tokens, " ");
    packages[cnt++] = tokens[1];
  }
}
END {
  out = "";
  for(i = 1; i <= cnt; i++) {
    out = out packages[i] " ";
  }
  print out;
}' debian/control`

case "${DEBDIST}" in
precise|trusty|jessie|raspbianjessie)
  BUILD_DEPS=`echo ${BUILD_DEPS} | sed -e 's/libpcre2-dev/libpcre3-dev/g'` ;;
esac

build() 
{
    $(dirname $0)/support/changelog "$CHANGELOG" "$DEBDIST" "$VER" 

    export JOBSARGS
    export JARGS
    export AUTOBUILD_CONFIGURE_EXTRA

    if ccache=$(which ccache); then
        echo "Using ccache" 
        ccache -s
        USE_CCACHE="--ccache" 
    else
        USE_CCACHE="" 
    fi

    export USE_CCACHE

    dpkg-buildpackage -b -us -uc

    for a in ../tvheadend*${VER}*.deb; do
        versioned_artifact "$a" deb application/x-deb `basename $a`
    done

    for a in ../tvheadend*${VER}*.changes; do
        versioned_artifact "$a" changes text/plain `basename $a`
    done
}

clean() 
{
    for a in ../tvheadend*${VER}*.deb; do
        rm -f "$a" 
    done

    for a in ../tvheadend*${VER}*.changes; do
        rm -f "$a" 
    done

    rm -f ${CHANGELOG}
    dh_clean
}

deps() 
{
    if [[ $EUID -ne 0 ]]; then
        echo "Build dependencies must be installed as root" 
        exit 1
    fi
    apt-get -y install ${BUILD_DEPS}
}

buildenv() 
{
    echo $BUILD_DEPS | shasum | awk '{print $1}'
}

eval $OP

What process calls the methods: build(), clean(), deps and buildenv()?
What is calling the configure script, the make and make install commands?
What script or routine makes use of the build options in the AUTOBUILD_CONFIGURE_EXTRA environment variable?

Cheers,

Flex