ci: added linting for changelog and version

scripts/lint_changelog.sh

 #!/usr/bin/env bash
 
 # diff the file silently, while still printing errors
-git diff --exit-code ${CI_DEFAULT_BRANCH}:${CHANGELOG_FILE} ${CHANGELOG_FILE} >/dev/null
+git diff --exit-code origin/${CI_DEFAULT_BRANCH}:${CHANGELOG_FILE} ${CHANGELOG_FILE} >/dev/null
 
 # exit code of 0 indicates non changed file
 if [ $? -eq 0 ]; then

scripts/lint_version.sh

 #!/usr/bin/env bash
 
 # obtain the default version
-default_version=$(git show ${CI_DEFAULT_BRANCH}:${CHART_FILE} | grep -oP 'version: \K(.*)')
+default_version=$(git show origin/${CI_DEFAULT_BRANCH}:${CHART_FILE} | grep -oP 'version: \K(.*)')
 
 # check for command error
 if [ $? -ne 0 ]; then