To understand Access-Control-Allow-Origin
header, I highly recommend How does Access-Control-Allow-Origin header work?
When Site A tries to fetch content from Site B, Site B can send an
Access-Control-Allow-Origin response header to tell the browser that
the content of this page is accessible to certain origins. (An origin
is a domain, plus a scheme and port number.) By default, Site B's
pages are not accessible to any other origin; using the
Access-Control-Allow-Origin header opens a door for cross-origin
access by specific requesting origins.
If your GitLab is hosted on gitlab.com, I don't see a way to add your domain to response header.
The easiest solution is wrapping XMLHttpRequests to GitLab in requests to your application - and on the backend you will simply fetch and return data. For example, you won't send a XML request to https://gitlab.com/pdaw/test/raw/master/README.md
, but tohttps://my.app.com/fetch-file?file=pdaw/test/raw/master/README.md
. On the backend of the fetch-file
action you will fetch and return raw data from https://gitlab.com/pdaw/test/raw/master/README.md