If you get the following error messages:
svn: Commit failed (details follow):
svn: Could not use external editor to fetch log message; consider setting the $SVN_EDITOR environment variable or using the --message (-m) or --file (-F) options
svn: None of the environment variables SVN_EDITOR, VISUAL or EDITOR is set, and no 'editor-cmd' run-time configuration option was found
use the following command in the shell:
export SVN_EDITOR=nano