Merge from the master branch flags all files as modified

[bnimit]

This might be a noob question but I need some inputs if possible ? I am using the action to identify all the files that have been changed during a feature branch changes. And I run some checks intended on only the files changed in the feature branch to make sure they don't violate a rule. But when I merge master all the changes from the merge as also detected as modified files that ruins the rule setup.

Any idea on how to work around this issue ? Can we restrict the changes to be just from the feature branch even when a master is merged during the development ?