title: error: pathspec 'tut51.cpp' did not match any file(s) known to git
body: <p>i have a file named <strong>tut51.cpp</strong> i have already commited it before and pushed it to my github, but by mistakenly i have made changes to my file.</p>
  <p>And now my file is in  modified status, how can i reverse the modified changes,
  <a href="https://i.stack.imgur.com/hDeS4.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/hDeS4.png" alt="enter image description here" /></a></p>
  <p>I tried git checkout but it shows me error.
  <a href="https://i.stack.imgur.com/HqiSa.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HqiSa.png" alt="enter image description here" /></a></p>