Per project
git config core.fileMode falseGlobal
git config --global core.fileMode falseWarning
Changes of the global setting won’t be applied to existing repositories. Additionally, git clone and git init explicitly set core.fileMode to true in the repo config as discussed in Git global core.fileMode false overridden locally on clone
Warning 2
core.fileMode is not the best practice and should be used carefully. This setting only covers the executable bit of mode and never the read/write bits. In many cases you think you need this setting because you did something like chmod -R 777, making all your files executable. But in most projects most files don’t need and should not be executable for security reasons.
The proper way to solve this kind of situation is to handle folder and file permission separately, with something like:
find . -type d -exec chmod a+rwx {} \; # Make folders traversable and read/write
find . -type f -exec chmod a+rw {} \; # Make files read/write
If you do that, you’ll never need to use core.fileMode, except in very rare environment.