I tried to upload my code to a repository on GitHub.
These are the commands I used:
git add .
git commit -m "text"
git push
However, instead of uploading the code to the main branch on GitHub, it created a master branch on my repository.
It looks like this now, with "main" shown first, then "master":
May I ask how can I merge these two branches?
You can merge these two branches with:
git switch <branch you want to merge to>
git merge <branch you want to merge onto the current branch>
git branch -d <branch name> //Optional, will delete the branch
To avoid this issue with future repositories, you can run this command:
git config --global init.defaultBranch main
It tells git to name the default branch 'main' instead of 'master' when using 'git init'.
For further information on branches take a look at this: Github - Manage branches
This is effectively a duplicate of How to merge main and master branches? My answer there, however, is much longer and more general: it covers your specific case, but your specific case is quite simple as you have nothing interesting on your GitHub main. You can just replace your existing GitHub main with what you currently call master, using:
git branch -m main
git push --force origin main
from your computer (your laptop). Normally, git push --force (or even git push --force-with-lease) is something to use carefully at best. Here, you're using it carefully—though you may not yet know it.
I recommend you read through the more complete answer here, but given the two images you show in your original question, the "overwrite main" method shown above should suffice.