Command below will tell git you want to start ignoring the changes to the file:
$ git update-index --assume-unchanged path/to/file
When you want to start keeping track again:
$ git update-index --no-assume-unchanged path/to/file
Command below will tell git you want to start ignoring the changes to the file:
$ git update-index --assume-unchanged path/to/file
When you want to start keeping track again:
$ git update-index --no-assume-unchanged path/to/file