Implement https://github.com/AppImage/AppImageSpec/blob/master/draft.md#github-releases

Author: probonopd

AppImageUpdate.AppDir/usr/bin/appimageupdate

@@ -146,11 +146,29 @@ if [ "$TYPE" == "zsync" ] ; then
  # .part appended, so it will automatically find previously interrupted zsync
  # downloads and reuse the data already downloaded.
  ZSYNC_URL=$(echo "${APPLICATION_USED}" | cut -d "|" -f 2) # Get the URL of the zsync file
+ echo "$ZSYNC_URL"
  # Get the file with zsync using $1 as an input file
  zsync_curl -I -i "${ISO}" "${ZSYNC_URL}" 2>&1
  NEWFILE=$(basename "${ZSYNC_URL}" | sed -e 's|.zsync||g' ) # FIXME: Use the file that zsync has written!!!
  chmod --reference="${ISO}.zs-old" "$(printf '%b' "${NEWFILE//%/\\x}")" # Set the same permissions as for the original file
  gpg_check
+elif [ "$TYPE" == "gh-releases-zsync" ] ; then
+ cd $(dirname "${ISO}") 
+ echo "Getting version information from GitHub Releases"
+ USERNAME=$(echo "${APPLICATION_USED}" | cut -d "|" -f 2)
+ REPO=$(echo "${APPLICATION_USED}" | cut -d "|" -f 3)
+ RELEASE=$(echo "${APPLICATION_USED}" | cut -d "|" -f 4)
+ FILENAME=$(echo "${APPLICATION_USED}" | cut -d "|" -f 5)
+ URL="https://api.github.com/repos/$USERNAME/$REPO/releases/$RELEASE"
+ REGEX=$(echo $FILENAME | sed -e 's|\*|\.\*|g')
+ echo "$REGEX"
+ ZSYNC_URL=$(curl "$URL" | grep "$REGEX" | grep "browser_download_url" | cut -d '"' -f 4) # TODO: Get rid of curl command
+ echo "$ZSYNC_URL"
+ # Get the file with zsync using $1 as an input file
+ zsync_curl -I -i "${ISO}" "${ZSYNC_URL}" 2>&1
+ NEWFILE=$(basename "${ZSYNC_URL}" | sed -e 's|.zsync||g' ) # FIXME: Use the file that zsync has written!!!
+ chmod --reference="${ISO}" "$(printf '%b' "${NEWFILE//%/\\x}")" # Set the same permissions as for the original file
+ gpg_check
 elif [ "$TYPE" == "bintray-zsync" ] ; then
  cd $(dirname "${ISO}") 
  # Actually, instead of copying another zsync file to a fixed URL (which is cumbersome)
@@ -176,6 +194,7 @@ elif [ "$TYPE" == "bintray-zsync" ] ; then
  echo "Latest version: ${VERSION}"
  fi
  ZSYNC_URL=$(echo "${DUMMY_URL}" | sed -e "s|_latestVersion|$VERSION|g" )
+ echo "$ZSYNC_URL"
  # Get the file with zsync using $1 as an input file
  zsync_curl -I -i "${ISO}" "${ZSYNC_URL}" 2>&1
  NEWFILE=$(basename "${ZSYNC_URL}" | sed -e 's|.zsync||g' ) # FIXME: Use the file that zsync has written!!!