You can quickly bring up an development environment using docker.
First make sure you have docker and docker-compose installed.
Then simply
docker-compose up
You can then browse to http://localhost:8080 and edit your files locally.
Use github & git svn, see http://teleogistic.net/2011/05/revisiting-git-github-and-the-wordpress-org-plugin-repository/
- edit readme.txt to bump up stable tag
- edit external-videos.php bump up stable tag there, too
- commit to github: git push origin master (possibly after merging a branch)
- git rebase trunk (to rebase the svn trunk to current master)
- git svn dcommit (to send commits to wordpress.org)
- git svn tag 0.22 (add new release)
- git tag -a 0.22 git push --tags (push tags to github also)
- git pull --rebase origin master git push origin master (to get svn tags to github)
Old process with SVN: http://wordpress.org/extend/plugins/about/svn/