svn propedit — Edit the property of one or more items under version control. See svn propset later in this chapter.
Edit one or more properties using your favorite
            editor.  The first form edits versioned properties in
            your working copy, and the second edits unversioned
            remote properties on a repository revision
            (TARGET determines only which
            repository to access).
--editor-cmd EDITOR --encoding ENC --file (-F) ARG --force --force-log --message (-m) ARG --revision (-r) REV --revprop --with-revprop ARG
svn propedit makes it easy to modify properties that have multiple values:
$ svn propedit svn:keywords  foo.c 
    <svn will launch your favorite editor here, with a buffer open
    containing the current contents of the svn:keywords property.  You
    can add multiple values to a property easily here by entering one
    value per line.>
Set new value for property 'svn:keywords' on 'foo.c'