This is a multi-branch (trunk and stable-0.7.3) patch which simply adds two session-related configuration-directive stubs to ./config/environment.rb.

The given stubs are for:

• @session_key@
• @session_path@

I created (and provide) this patch due to the fact that one of both directives is required to run multiple Redmine (or other apps which use the same session-names as Redmine) deployments on the same domain (though seperate installs under several different sub-URI's) without suffering from session-mangling.
Both directives aren't documented (sufficiently) imho at the Redmine website or the Redmine Code-base. That is the reason why I'd propose to add something like provided with this patch. If it is not taken into the project I would propose to add an entry to the Redmine FAQ about these issues. I am volunteering already... :-)

I already found some related issues and threads:

• #540
• #1041
• http://www.redmine.org/boards/2/topics/show/150#message-163

Both issues contain comments which faulty "documents" the session_key directive. This faultyness is due to the fact that rake will crash if the session_key directive is used in ./config/enviroment.rb as commented in both issues probably caused by the rake-scripts which aren't accepting Rails 2.1 syntaxis.
The mentioned forum-thread gives to correct syntaxis though it is mixed with another config-directive in some another case.

Beware: This patch only adds config-stubs which solves the session-mangling behaviour in the given environment. It does not fix any related problems with the so-called autologin-cookie. I created a sepereate specific issue for that (#1763).
See also #540 and partly #982 regarding the problems with the autologin-cookie.