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Git - Undoing Committed Changes

From EdWiki

GitLab - Undoing Committed Changes

  • Goals
    Learn how to revert changes that have been committed to a local repository.
  • Undoing Commits
    Sometimes you realized that a change that you have already committed was not correct and you wish to undo that commit. There are several ways of handling that issue, and the way we are going to use here is always safe. Essentially we will undo the commit by creating a new commit that reverses the unwanted changes.
  • Change the file and commit it.
    Change the hello.c file to the following.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char* argv[]) {
    if( argc > 1 ) {
        puts("Hello ");
        puts(argv[1]);   /* This is an unwanted but committed change */
    } else {
        puts("Hello World!!!"); /* prints !!!Hello World!!! */
    }
    return EXIT_SUCCESS;
}
git add hello.c
git commit -m "Oops, we didn't want this commit"
  • Create a Reverting Commit
    To undo a committed change, we need to generate a commit that removes the changes introduced by our unwanted commit.
git revert HEAD

This will pop you into the editor. You can edit the default commit message or leave it as is. Save and close the file.

Since we were undoing the very last commit we made, we were able to use HEAD as the argument to revert. We can revert any arbitrary commit earlier in history by simply specifying its hash value.

Note: The --no-edit in the output can be ignored. It was necessary to generate the output without opening the editor.

  • Check the log
    Checking the log shows both the unwanted and the reverting commits in our repository.
git hist

This technique will work with any commit (although you may have to resolve conflicts). It is safe to use even on branches that are publicly shared on remote repositories.

  • Up Next
    Next, let’s look at a technique that can be used to remove the most recent commits from the repository history.