Merge branch '66-variables-sh-uses-too-long-branch-names-sometimes' into 'master'

Resolve "variables.sh uses too long branch names sometimes."

Closes #66

See merge request openappstack/wordpress-helm!31

variables.sh

-# Set the docker image tag to the current branch:
-dockerTag=$(git rev-parse --abbrev-ref HEAD)
+# Set the docker image tag to the name of the current branch.
+# Shortened to 63 bytes because Gitlab does the same with the `CI_COMMIT_REF_SLUG`
+# variable, which we use in the CI script to build the docker image.
+dockerTag=$(git rev-parse --abbrev-ref HEAD | cut -b "-63")
 
 # Only get the number from the issue (or whatever is in front of a dash
 # otherwise) for the release name