All the work, that is done on In-Portal is being committed in SVN repository. If there is a need to recall some of it later there are 2 ways right now:
- search issue tracker
- search google groups
However if there is a need to search through a code-base in every code change that was made in each period of time, then there are no way to do it.
Here is a solution I've came up while surfing the web: http://svnquery.tigris.org/. It allows to index all content of repository (how much exactly can be specified via settings) and then use Google-alike search queries to find info.
For example if you remember, that some interesting code were having "this" word in it and it was in "test.php" file, then you can easily form a search query to find exactly it.
There is something similar build-in on GitHub.