git-update-index

Mark file as unchanged

$ git update-index --assume-unchanged [file]

$ git update-index --no-assume-unchanged [file]

$ git update-index --skip-worktree [file]

$ git update-index --refresh

$ git update-index --add [file]

$ git update-index --remove [file]

git update-index [options] [files...]

git update-index registers file contents in the working tree to the index. It is a low-level plumbing command used internally by `git add`.
The most common use is the `--assume-unchanged` flag, which tells Git to temporarily ignore changes to a tracked file. The `--skip-worktree` flag serves a similar purpose but is intended for files managed by sparse checkout.

--assume-unchanged

Ignore changes to file.

Track changes again.

Skip worktree bit.

Clear skip-worktree.

Add file to index.

Remove file from index.

Refresh stat info.

Set executable bit.

git-add(1), git-rm(1)