Trac browser URL can not always be created by appending the Trac URL and the changed file path.
Sometimes the file path must be truncated (see JENKINS-7032), sometime the file path must be extended by a prefix.

Example for Truncate
The link will then point at:
http://trac.mycompany.com/trac-project/browser/Product/Trunk/subdir/file.txt
But my Trac installation has its root at Product/Trunk/, so the only link that would work is:
http://trac.mycompany.com/trac-project/browser/subdir/file.txt

Example for Prefix
Only the path to the file is included resulting in incorrect urls. So for example, I get this incorrect url:
http://trac.mycompany.com/browser/myfile.py
instead of this correct url:
http://trac.mycompany.com/browser/myrepo/myfile.py