svn: reverting to previous version -

I mistakenly changed the file, for a simple example we call it foo.txt:

foo.txt, rev 300 (true):

  e = MC ^ 2  

foo.txt, rev 301 (wrong):

  e = mc ^ 3  

How do I commit again in the next 300? If I update rev3 for rev 300, then I get the correct file but its position is correct & amp; There is no need to be committed.

Note: This is only foo.txt which I want to return. Other amendments in RAV 301 are important and I need to keep them.

  svn merge - R301: 300 foo.txt svn commit -m 'foo.txt Back to 300 '