To revert changes in a single file using Git, you can use the following command:

git checkout HEAD filename.ext

This will revert the changes in the specified file filename.ext to the latest committed version. The HEAD reference points to the latest commit in the current branch.

The git checkout command allows you to switch to a specific version of your code repository or to undo changes in a specific file.

In the case of reverting changes to a single file, the command git checkout HEAD filename.ext retrieves the version of the file that is stored in the latest commit and replaces the current version of the file with that version.

HEAD is a reference to the latest commit in the current branch, so when you run git checkout HEAD filename.ext, it checks out the version of the file that was committed in the latest commit.

It’s worth noting that using git checkout does not destroy any information, as the changes remain in your repository’s history and can be accessed and restored if needed.

It’s always a good idea to make a backup copy of the file before checking out an older version, in case you need to reference the changes you are discarding.

Example

Here’s an example of how you can use git checkout to revert changes to a TypeScript file named index.ts:

$ git checkout HEAD index.ts

This command retrieves the version of index.ts stored in the latest commit and replaces the current version of the file with that version. If you have made any changes to index.ts that have not yet been committed, those changes will be lost.

It’s always a good idea to make a backup copy of the file before checking out an older version, just in case you need to reference the changes you are discarding.

Revert a file from Staging

If you have already added the file to the staging area using git add, you will need to unstage the file before you can revert its changes. Here’s how you can do it:

$ git reset HEAD filename.ts
$ git checkout HEAD filename.ts

The first command, git reset HEAD filename.ts, unstages the file filename.ts from the staging area, effectively removing it from the list of files that will be included in the next commit.

The second command, git checkout HEAD filename.ts, retrieves the version of the file stored in the latest commit and replaces the current version of the file with that version.

This will effectively undo both the changes in the file and the git add command, and you should now be back to the state you were in before you staged the file.

Revert a committed file

If you have already committed the file and want to revert it to the last commit, you can use the following command:

$ git checkout HEAD^ filename.ts

The HEAD^ reference points to the second-to-last commit in the current branch, so using git checkout HEAD^ filename.ts checks out the version of the file that was committed in that commit. This effectively reverts the file to the state it was in before the latest commit.

It’s worth noting that this will not destroy any information, as the changes will remain in your repository’s history and can be accessed and restored if needed.