svn behind squid proxy

You need to edit the servers file located at your HOME DIRECTORY

Also need to make changes in squid configuration file.
Need to make sure the proxy server itself supports all the HTTP methods Subversion uses.
Some proxy servers do not support these methods by default: PROPFIND, REPORT, MERGE, MKACTIVITY, CHECKOUT.

To allow these method depends on particular proxy software used.

For Squid, you need to edit config file by

vi /etc/squid/squid.conf

and need to check config option are

#  TAG: extension_methods
#       Squid only knows about standardized HTTP request methods.
#       You can add up to 20 additional "extension" methods here.
#
#Default:
# none
extension_methods REPORT MERGE MKACTIVITY CHECKOUT