I'm talking about a portable issue tracker format that ideally uses something like git as its transport (but note: this does not mean that the issue database would travel along with the application's source code! That might be nice as an option but not by design). command-line and web-based front ends can then refer to it. Fossil, OTOH, looks like a huge monolithic web application / version control system / issue tracker / kitchen sink written in very hard-coded C.
Looking through some docs, Fossil is anti-git and it claims its own DVCS is a great improvement over git: http://fossil-scm.org/index.html/doc/trunk/www/quotes.wiki. Because Fossil has every possible feature packed all into one monolithic executable, rather than relying upon existing systems like diff, patch, etc. this means Fossil is "the opposite of bloat": http://fossil-scm.org/index.html/doc/trunk/www/qandc.wiki (in fact that is the opposite of the opposite of bloat....)
http://fossil-scm.org/index.html/doc/trunk/www/index.wiki