This feature will reduce Jira server storage by deleting files from cloned git repositories after indexing. Discarding files can save disk space but may limit some features such as displaying diffs of files.
There are three options to choose from:
Keep all cloned binary files. No storage savings. All features available This option will leave all cloned repositories intact.
Discard all files that match the mask below. Some features limited. This option will delete all files in the cloned repositories matching the declared file extensions.
Discard all files EXCEPT those that match the mask below. Some features limited. This option will delete all other files in the cloned repositories except those files with extensions declared.
Select any option with the discard label to enable editing of the file mask field.
More on general settings
Discard cloned files in Jira HOME directory setting (this page)