Should not use $SSH_AUTH_SOCK as the file name to create the sock file

[kailiu42]

First of all thanks for the tool, it's great as it precisely solved the problem.

As to the issue mentioned in the subject, $SSH_AUTH_SOCK is used to let programs know "what is the existing SSH agent socket path that I should connect to", but not "where I should create my agent socket file".

In current case, the existing $SSH_AUTH_SOCK file got overwritten by this program if it is already set by other program, such as keeagent, a plugin of keepass. Keeagent can create cygwin and msysGit compatible socket files, so some Windows users use it to manage SSH keys and already have the $SSH_AUTH_SOCK points to the socket file create by it.

So I would like to suggest either using a different env. var. or a command line option.