Identify one revision before the commit you need to update. In the following example, the last two commits are going to be updated.
Run git rebase command with the identified commit number: git rebase -i 2778751
In the editor, for each commit you need to update, change the word pickto edit. (Make sure you know how to use the Vim editor)
Run the following command to set the author to the current configured git user: git commit --amend --reset-author --no-edit
Or use the following to set it to a custom author: git commit --amend --no-edit --author="Author Name <email@example.com>"
Run git rebase --continue
Repeat step 4 and 5 until all of the commits are updated.