Use include for macros and other definitions in gitlab-env
The following discussion from !35 should be addressed:
@snuverink_j for HTML and PDF translation this macros should be defined only once. To make the links working in the Gitlab GUI they must be defined in all files. The best solution would be to create a new file for these and future macro definition and include this file.
For HTML and PDF translation it must be included in a
ifdef::backend-docbook5,backend-html5block of the master file
For the Gitlab GUI the file must be included in a
it doesn't seem to work
😞.. I forgot (again) that the include directive was not properly supported in gitlab.
Finally, this has been fixed: https://gitlab.com/gitlab-org/gitlab-foss/-/merge_requests/28417, but only in 12.0 and we are on 11.9.
Once we are on gitlab version 12 the header of each file should be replaced by a single include to reduce duplication.