I was writing a simple script in the school computer, and committing the changes to Git (in a repo that was in my pendrive, cloned from my computer at home). After several commits I realized I was committing stuff as the root user.
Is there any way to change the author of these commits to my name?
Changing the author (or committer) would require re-writing all of the history. If you're okay with that and think it's worth it then you should check out git filter-branch. The main page includes several examples to get you started. Also note that you can use environment variables to change the name of the author, committer, dates, etc. -- see the "Environment Variables" section of the git man page.
Specifically, you can fix all the wrong author names and emails for all branches and tags with this command (source: GitHub help):
#!/bin/sh git filter-branch --env-filter ' OLD_EMAIL="email@example.com" CORRECT_NAME="Your Correct Name" CORRECT_EMAIL="firstname.lastname@example.org" if [ "$GIT_COMMITTER_EMAIL" = "$OLD_EMAIL" ] then export GIT_COMMITTER_NAME="$CORRECT_NAME" export GIT_COMMITTER_EMAIL="$CORRECT_EMAIL" fi if [ "$GIT_AUTHOR_EMAIL" = "$OLD_EMAIL" ] then export GIT_AUTHOR_NAME="$CORRECT_NAME" export GIT_AUTHOR_EMAIL="$CORRECT_EMAIL" fi ' --tag-name-filter cat -- --branches --tags