Update the root directory of a branch from the subdirectory of another

Question

Developing on github, I often maintain a html/ or _site/ subdirectory in my master branch where I generate web-based documentation for the project.

Answer 1

To start your gh-pages branch:

true | git mktree | xargs git commit-tree | xargs git branch gh-pages

To fetch anything you want into it, say the html directory from the master branch, read-tree and commit:

git checkout gh-pages
git read-tree master:html
git commit -m'gh-pages documentation'
git push origin gh-pages
git checkout master

and you're done.

Late addition: there's a shorter sequence for adding to the gh-pages branch:

git commit-tree -p gh-pages -m "" master:html \
| xargs git update-ref refs/heads/gh-pages

which doesn't require flushing the current working tree