1.create a new repository on the command line

git init
git add README.md
git commit -t "first commit"
git remote add origin https://github.com/chengxxf/pthbase.git
git push -u origin master

2.push an existing repository from the command line

git remote add origin https://github.com/chengxxf/pthbase.git
git push -u origin master

#################stackoverflow###################
To definitely be able to login using https protocol, you should first set your authentication credential to the git Remote URI:

git remote set-url origin https://yourusername@github.com/user/repo.git
Then you'll be asked for a password when trying to git push.

In fact, this is on the http authentication format. You could set a password too:

https://youruser:password@github.com/user/repo.git
You should be aware that if you do this, your github password will be stored in plaintext in your .git directory, which is obviously undesirable.
###################################################

#########################
Changing a remote's URL
https://help.github.com/articles/changing-a-remote-s-url/
########################

QUESTION: git produces Gtk-WARNING: cannot open display
ANSWER: unset SSH_ASKPASS

#######rebase branches to master##############

git checkout master
git pull
git checkout local_branch_name
git rebase master
git push --force # force required if you've already pushed