bug#79488: [RFE] Enhancement idea : Better Handling of File Permission with CHMOD Command

Hello coreutils team,

I would like to suggest an improvement to the "CHMOD" utility in GNU coreutils.

Current behaviour:
-----------------------
The chmod command allows us to change file permissions. However, in the current implementation, it does not support granting permissions for a specific time period.

Suggestion for improvement:
-----------------------------------
Introduce a new time flag (for example, `-t`) that accepts a duration in minutes. With this option, users could grant permissions to a file for a specific time period instead of permanently. Once the specified time expires, the file's permissions would automatically revert to their default state.

Example (if possible):
--------------------------
$ chmod 777 -t 30 myfile.txt
# Grants full access to "myfile.txt" for 30 minutes
# After 30 minutes, permissions revert to their previous state

Ex :

Current:
   $ls -al
   -r--r--r-- 1 user user 1.1G Sep 18 10:20 file.iso
   $ chmod 777 file.iso
   -rwxrwxrwx 1 user user 1.1G Sep 18 10:20 file.iso

Proposed with `-t`:
   $ chmod 777 -t 15 file.iso
   -rwxrwxrwx 1 user user 1.2G Sep 18 10:20 file.iso
After 15 min
   -r--r--r-- 1 user user 1.2G Sep 18 10:20 file.iso

Rationale:
------------
This feature would be useful in scenarios where temporary access needs to be granted, such as:
- Allowing a colleague or process to access a file for a short duration
- Enhancing security by automatically revoking access after the required time window
- Reducing the risk of leaving sensitive files over-exposed due to forgotten manual permission changes

Environment:
----------------
- OS/Distribution: Ubuntu 22.04
- Coreutils version: cmod (GNU coreutils) 9.1

Thank you for maintaining coreutils and considering this suggestion.

Best regards,
S. Mahish Sivan