If the permission of a file changes inside a git repository, Git identifies that as a changed file even though you haven’t changed that file. For example if you change a file’s permission from 644 to 755, It will be shown as a modified file. If you don’t want this to be shown as a modified file.
git config core.fileMode false
and if you want to change it for all the git repository in your system.
git config --add --global core.filemode false