WordPress Subversion repository - markhowellsmead/helpers GitHub Wiki
Refer to https://developer.wordpress.org/plugins/wordpress-org/how-to-use-subversion/ for full details. This page is purely for my reference.
Get
svn co https://plugins.svn.wordpress.org/PLUGINNAME PLUGINNAME
Update
cd PLUGINNAME
svn up
Edit files. Then:
svn diff
svn ci -m 'MESSAGE'
svn cp trunk tags/1.1.0
svn ci -m 'Tagging version 1.1.0'