To start ignoring files in git:

git update-index --assume-unchanged <path/to/file1> <path/to/dir2>

To track the change of the specific file again:

git update-index --no-assume-unchanged <path/to/file1> <path/to/dir2>

To track all the files that are ignored temporarily:

git update-index --really-refresh

To see the list of temporarily ignored files:

git ls-files -v | grep "^h"

Example

$ git status

# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
# 	modified:   file-to-be-ignored-temporarily.txt
# 	modified:   file-want-to-see-change.txt
# 
# no changes added to commit (use "git add" and/or "git commit -a")

$ git update-index --assume-unchanged file-to-be-ignored-temporarily.txt

$ git status

# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
# 	modified:   file-want-to-see-change.txt
# 
# no changes added to commit (use "git add" and/or "git commit -a")

$ git update-index --no-assume-unchanged file-to-be-ignored-temporarily.txt

$ git status

# On branch master
# Changes not staged for commit:
#   (use "git add <file>..." to update what will be committed)
#   (use "git restore <file>..." to discard changes in working directory)
# 	modified:   file-to-be-ignored-temporarily.txt
# 	modified:   file-want-to-see-change.txt
# 
# no changes added to commit (use "git add" and/or "git commit -a")

Note: In case some files need to be ignored all the time, it is better ignore the file in the .gitignore.