$ git init
Initialized empty Git repository in /tmp/tmp.GZDn8I0piH/.git/
$ echo abc > file
$ git add file
$ git commit -m "Initial commit."
[master (root-commit) 22fd7a1] Initial commit.
 1 file changed, 1 insertion(+)
 create mode 100644 file
$ echo 123 >> file
$ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   file

no changes added to commit (use "git add" and/or "git commit -a")
$ rm .git/index
$ git reset
Unstaged changes after reset:
M	file
$ git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   file

no changes added to commit (use "git add" and/or "git commit -a")
$ cat file
abc
123