how to ignore a particular file in git code example

Example: git exclude some files from git commit

To exclude some files from git commit
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syntax  - git update-index --assume-unchanged <filepath>
example - git update-index --assume-unchanged default/config.php

To undo the above command
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syntax  - git update-index --no-assume-unchanged <filepath>
example - git update-index --no-assume-unchanged default/config.php