Redmine

+1

I think this information should be known more.

Change import statement
@import url(../../../stylesheets/application.css);

to some other name (e.g. application_v2.css)

Rename public/stylesheets/application.css to e.g. application_v2.css

A "better" workaround is to append a ?version tag instead of renaming the file, that way you don't have to modify redmine internal files. The downside still being that you have to remember to update your theme everytime you upgrade redmine..

Example:

 @import url(../../../stylesheets/application.css?4.3.2);

So I also modified the cache directive from https://www.redmine.org/projects/redmine/wiki/BrowserCaching#The-work-round-for-RedMine

I decided to stop caching any files which don't have the ?version tags. At least on redmine 4.2.3, the vast majority of the files have this tag. Only leaving out a few images which are loaded from application.css

-  # the regex logic: after either /javascripts/ or /stylesheets/ find the suffixes we want, followed by any quantity of numbers 0-9
+  # the regex logic: after either /javascripts/ or /stylesheets/ find the suffixes we want, followed by one or more numbers 0-9
   # This works because the files we want to cache always appear after one of those 2 directories:  but not the files we want to ignore
   # /journals/edit/24174.js  and /uploads.js?attachment_id=1&filename=my-file-to-upload.png
-  location ~* {{REDMINE_RELATIVE_URL_ROOT}}(?<file>/(?:(?:plugin_assets/|themes/).+)?(?:javascripts|stylesheets|images|favicon)/.+(?:css|js|jpe?g|gif|ico|png|html)(\?[0-9]+)?$) {
+  location ~* {{REDMINE_RELATIVE_URL_ROOT}}(?<file>/(?:(?:plugin_assets/|themes/).+)?(?:javascripts|stylesheets|images|favicon)/.+(?:css|js|jpe?g|gif|ico|png|html)(\?[0-9]+)$) {