Errors in current state of pre-commit script

[spenke91]

Bug report

Describe the bug
While working in t8code, I today realized two things regarding the pre-commit script:

1. Since I copied the pre-commit script into .git/hooks as described in the Coding Guidelines, the names of the scripts for checking macros and indentation had changed. As a result, my pre-commit hook did not find them and thus always reported every file as not indented.
   My suggestion to fix this would be to change the coding guidelines, such that it suggests linking the script from scripts/pre-commit into.git/hooks/ rather than copying it. This way, any changes in the pre-commit script would automatically be applied within the hook. (This does require a minor update of how to handle the paths, as you will see in the associated PR.)

2. After figuring out the issue described in 1., I switched to the latest state of the pre-commit script and found some errors there. My guess is that some local changes have accidentially been pushed to origin, because of:

   # This is the indent script in the project's directory
   echo "test"
   GIT_DIR= git rev-parse --git-dir
   echo "$GIT_DIR"
   echo "test2"
   CHECK_INDENT=$GIT_COMMON_DIR/scripts/check_if_file_indented.sh
   
   CHECK_MACROS=$GIT_COMMON_DIR/scripts/check_macros.sh
   

   My suggestion to fix this will be outlined in a PR I will open next, that is, Bugfix: Fix wrong paths in pre-commit script #1535.

To Reproduce
Feel free to try the current version of pre-commit for yourself

Expected behavior

Log files

Environment (please complete the following information):

• Teamserver

Estimated priority

"Priority: high" Should be solved as soon as possible

Additional context