#Try git show-ref to see what refs you have. Is there a refs/heads/master?
#Due to the recent "Replacing master with main in GitHub" action,
#you may notice that there is a refs/heads/main. As a result,
#the following command may change
#from ---> git push origin HEAD:master
#to ---> git push origin HEAD:main
#You can try
git push origin HEAD:master
#as a more local-reference-independent solution. This explicitly states
#that you want to push the local ref HEAD to the remote ref master
#(see the git-push refspec documentation).

# Git commands one can use to push the local repository to github repo
git init
git add .
git commit -m "First Commit"
git remote add origin url_to_repo
git push origin main
# If you get error such as below
# error: src refspec main does not match any
# error: failed to push some refs to 'Repo url'
# Then use below command to push the code.
git push origin HEAD:main

mkdir repo && cd repo
git remote add origin /path/to/origin.git
git add .
/*Make sure you commit before push to github*/
git commit -m "initial commit"
git push origin master

mkdir repo && cd repo
git remote add origin /path/to/origin.git
git add .
git commit -m "initial commit"
git push origin master

git push heroku HEAD:master

You probably forgot to add your your changes to staging area.
So type :
git add .
then :
git commit -m "meesage"
finally :
git push origin branch_name

error: src refspec master does not match any.
error: failed to push some refs to 'ssh://xxxxx.com/project.git'