Github: Mirroring gh-pages to master

I'm developing a jQuery plugin that's being hosting on GitHub. It has a demo included of which I'm manually copying and pushing to the branch gh-pages, what I'd like to do is have it so when I push a change to master it is automatically pushed to gh-pages, or at least a setup where they are mirrored.

I've already seen this question but not sure if it really answers my question with regard to these requirements:

1. I use Tower, I don't mind using the terminal (Mac) to make changes to config, so long as the solution works with this GUI.
2. I only want this 'mirroring' on certain repos, not on all of them on my machine.

Cheers

Add the following 2 lines to the [remote "origin"] section of .git/config:

push = +refs/heads/master:refs/heads/gh-pages
push = +refs/heads/master:refs/heads/master

Every time you push it will automatically push master to gh-pages as well. I'm using this for the jQuery Lifestream project.

git checkout gh-pages
git merge master
git push origin gh-pages

Do not do what denbuzze suggests above!! The + (plus sign) in the push makes it quietly accept non-fastforward updates. I found out the hard way that this can irrevocably cause work to be lost by leading to dangling commits. Simply removing the plus signs makes this a safer approach.

push = refs/heads/master:refs/heads/gh-pages
push = refs/heads/master:refs/heads/master

now instead of causing a force update this will cause a warning & pull suggestion

To https://github.com/someuser/repo.git
 ! [rejected]        master -> gh-pages (fetch first)
 ! [rejected]        master -> master (fetch first)
error: failed to push some refs to 'https://github.com/someuser/repo.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

I'm adding further explanation to @denbuzze and @MCSDWVL answers.

If you want to push both to master and gh-pages automatically each time you run git push origin, you probably want to add a Refspec to the git config of your repo.

So, according to the git-scm book, you can add two RefSpecs, by adding two push values to the repo config file .git/config:

[remote "origin"]
url = https://github.com/<github_user>/<repo_name>
      fetch = +refs/heads/*:refs/remotes/origin/*
      push = refs/heads/master:refs/heads/master
      push = refs/heads/master:refs/heads/gh-pages

That will cause a git push origin to:

1. Push the local master branch to the remote master branch
2. Push the local master branch to the remote gh-pages branch

by default.

Note: using a + before the spec causes to force push to the repo. Use it with caution:

> The format of the refspec is an optional +, followed by <src>:<dst>, where <src> is the pattern for references on the remote side and <dst> is where those references will be written locally. The + tells Git to update the reference even if it isn’t a fast-forward.

I personally like to wrap this in an alias:

alias gpogh="git checkout gh-pages && git merge master && git push origin gh-pages && git checkout -"

This mirrors your master to gh-pages, pushes to github, then switches back the previous branch you were working on.

commit and push to master..

then :

git checkout gh-pages  // -> go to gh-pages branch
git rebase master // bring gh-pages up to date with master
git push origin gh-pages // commit the changes
git checkout master // return to the master branch

OR you can just use the cmd below, this will push your local master branch to gh-pages master branch. git push -f origin master:gh-pages

UPDATE: GitHub now allows pages to be published from any branch and directory you want.

---

It was much easier for me to use the gh-pages branch as master. There's nothing magical about "master"; it's just another branch name. There is something magical about gh-pages, because that's where GitHub is looking for index.html to serve your page.

Read more in my other answer on this topic.

Using gh-pages as master is also easier than subtrees, which are easier than mirroring. You could use git subtree as described here or here: if you have a directory which contains your demo, you can push that directory to the gh-branch with one command. Let's say you name the directory gh-pages to make things clear. Then after you've committed and pushed your changes to master, run this to update gh-pages:

git subtree push --prefix gh-pages origin gh-pages

The problem is if your files in gh-pages refer to files in other directories outside it. Symlinks don't work, so you'll have to copy files in the directory that serves as gh-pages.

If you use gh-pages as master, this problem won't occur.