Change your existing/saved SVN user to other user on your UNIX machine or MAC OSx

Locate and find your .subversion directory, mostly it will under your home directory.

.subversion/auth/svn.simple/random-numbered-file ( without extension )

for eg ( in my machine ) :

Jackys-MacBook:svn.simple gokulamurthy$ ls
772c71669d28a02d42addb1d967d1862
Jackys-MacBook:svn.simple gokulamurthy$ vi 772c71669d28a02d42addb1d967d1862

K 8
passtype
V 8
keychain
K 15
svn:realmstring
V 42
SVN Access
K 8
username
V 14
your-existing-svn-username
END

change your existing svn username to current username then save and close the file.

when you do any operation under your subversioned directory like svn ls , svn log, svn up, svn switch, etc., for any operations it will ask you enter the svn new username and password.

Thats all. Have Fun with SVN.

SVN log commands must be useful

SVN List of all files modified/added/deleted by a particular user:

svn log | sed -n '/username/ p'

For multiple users:
svn log | sed -n '/username/,/-----$/ p'

SVN List Comment and Files Changed for a Certain Revision:

svn log -v -r RevisionNo https://yoursvnurl.com

Hope this will help.