add Gitea update script

uberspace-gitea-installer.sh

@@ -40,6 +40,7 @@ function install_gitea
     --config "/home/${USER}/gitea/custom/conf/app.ini"
   uberspace web backend set / --http --port 9000
   uberspace web backend list
+  install_update_script
   printf "You can now access your $APP_NAME by directing you Browser to: \n https://%s.uber.space \n" "$USER"
 }
 
@@ -132,6 +133,111 @@ function verify_file
   fi
 }
 
+function install_update_script
+{
+  cat << 'end_of_content' > ~/bin/gitea-update
+#!/usr/bin/env bash
+
+APP_NAME=Gitea
+GITEA_LOCATION=$HOME/gitea/gitea
+TMP_LOCATION=$HOME/tmp
+GPG_KEY_FINGERPRINT=7C9E68152594688862D62AF62D9AE806EC1592E2
+
+ORG=go-gitea # Organisation or GitHub user
+REPO=gitea
+GITHUB_API_URL=https://api.github.com/repos/$ORG/$REPO/releases/latest
+
+function get_local_version
+{
+  LOCAL_VERSION=$($GITEA_LOCATION --version |
+    awk '{print $3}')
+}
+
+function get_latest_version
+{
+  curl --silent $GITHUB_API_URL > $TMP_LOCATION/github_api_response.json
+  TAG_NAME=$(jq --raw-output '.tag_name' $TMP_LOCATION/github_api_response.json)
+  LATEST_VERSION=${TAG_NAME:1}
+  DOWNLOAD_URL=$(jq --raw-output '.assets[].browser_download_url' $TMP_LOCATION/github_api_response.json |
+    grep --max-count=1 "linux-amd64")
+}
+
+function get_signature_file
+{
+  SIGNATURE_FILE_URL=$(jq --raw-output '.assets[].browser_download_url' $TMP_LOCATION/github_api_response.json |
+    grep "linux-amd64.asc")
+  rm $TMP_LOCATION/github_api_response.json
+  wget --output-document $TMP_LOCATION/gitea.asc "$SIGNATURE_FILE_URL"
+}
+
+function verify_file
+{
+  get_signature_file
+
+  ## downloading public key if it does not already exist
+  if ! gpg --fingerprint $GPG_KEY_FINGERPRINT
+  then
+    ## currently the key download via gpg does not work on Uberspace
+    #gpg --keyserver keys.openpgp.org --recv $GPG_KEY_FINGERPRINT
+    curl --silent https://keys.openpgp.org/vks/v1/by-fingerprint/$GPG_KEY_FINGERPRINT | gpg --import
+    echo "$GPG_KEY_FINGERPRINT:6:" | gpg --import-ownertrust
+  fi
+
+  if gpg --verify $TMP_LOCATION/gitea.asc $TMP_LOCATION/gitea
+  then rm $TMP_LOCATION/gitea.asc; return 0
+  else echo "gpg verification results in a BAD signature"; exit 1
+  fi
+}
+
+function do_update_procedure
+{
+  wget --output-document $TMP_LOCATION/gitea "$DOWNLOAD_URL"
+  verify_file
+  systemctl stop gitea
+  mv $TMP_LOCATION/gitea "$GITEA_LOCATION"
+  chmod u+x --verbose "$GITEA_LOCATION"
+  echo "Start gitea for upgrade"
+  systemctl start gitea
+  echo "Waiting for 10 seconds…"
+  sleep 10
+  echo "Restart gitea"
+  systemctl restart gitea
+}
+
+## this is a helper function to compare two versions as a "lower than" operator
+function version_lt
+{
+  test "$(echo "$@" |
+    tr " " "n" |
+    sort --version-sort --reverse |
+    head --lines=1)" != "$1"
+}
+
+function main
+{
+  get_local_version
+  get_latest_version
+
+  if [ "$LOCAL_VERSION" = "$LATEST_VERSION" ]
+  then
+    echo "Your $APP_NAME is already up to date."
+    echo "You are running $APP_NAME $LOCAL_VERSION"
+  else
+    if version_lt "$LOCAL_VERSION" "$LATEST_VERSION"
+    then
+      echo "There is a new version available."
+      echo "Doing update from $LOCAL_VERSION to $LATEST_VERSION"
+      do_update_procedure
+    fi
+  fi
+}
+
+main "${@}"
+exit $?
+end_of_content
+  chmod u+x --verbose ~/bin/gitea-update
+}
+
 function yes-no_question
 {
   local question=$1