The fossil-scm.org server gets between 1500 and 2000 distinct human visitors per day on weekdays. (Lower traffic on weekends. Robots are excluded from the count. "distinct" means visitors having different IP addresses.) This is perhaps orders of magnitude less than git-scm.org (I'm guessing - anybody have stats?) but it is also non-trivial. With ~1750 visitors per day somebody must be using it. And I would guess that most actual users do not visit the site daily. (When was the last time you visited git-scm.org?)
FWIW, today has already seen in excess of 10,000 distinct human IPs, likely due to this HN post.
Like most people, I go to Google which then redirects me to the correct Stack Overflow question/answer the most often. I think git-scm.org is mostly a guide to get started and the reference documentation.
Most projects are invisible to you, like in-house projects that never see the light of day. If Fossil is used by 1% of those projects, that's still a lot of projects.
How can you tell if Fossil is popular in HN? By my reading, only two people in this thread use it. More than that mention having never heard of it before, or make statements where it's clear they don't really understand what it is.
There's really no reason to think that Fossil is used internally at a rate higher than its public-facing usage. And I've literally never seen a project that uses Fossil aside from Fossil examples.
From https://news.ycombinator.com/from?site=fossil-scm.org there are 20 links to fossil-scm.org in the last 2 years. I manually looked at the last 2 years of submissions with "fossil" in the name and found an additional 4 which were not to fossil-scm.org.
It's over 50% higher for Mercurial. I counted about 30 postings with the name 'Mercurial' over the last two years, of which about 7 were from mercurial-scm.org. I left out some of the obvious duplicates.
You write "I've literally never seen a project that uses Fossil aside from Fossil examples".
How much effort did you put into looking, and would you have recognized one if you did?
After SQLite, the most widely used project which uses Fossil is likely Tcl. http://core.tcl.tk/tcl/wiki?name=Index says it uses Fossil 2.7. For obvious reasons, there is an affinity between Tcl projects and Fossil.
A search for '"This page was generated in" "Fossil"' in DDG finds some non-trivial active projects: https://duckduckgo.com/?q=%22This+page+was+generated+in%22+%... . "Active" means "commits in the last few weeks." For examples:
"MySQL++ is a C++ wrapper for MySQL’s C API" - https://tangentsoft.com/mysqlpp/home
"Jsi is a C (+/-) embeddable JavaScript interpreter" - https://jsish.org/fossil/jsi/doc/tip/www/home.wiki
"Cxxomfort (cxx as in C++, comfort as in comfort) is a small, header-only library that backports various facilities from more recent C++ Standards" - http://ryan.gulix.cl/fossil.cgi/cxxomfort/index
"SquirrelJME is intended to be a Java ME 8 compatible environment for strange and many other devices" - http://multiphasicapps.net/doc/ckout/readme.mkd
[0] https://fresh.flatassembler.net/fossil/repo/fresh/index [1] https://flatassembler.net/fossil/repo/fasmg/home
There is a online hosting service: http://chiselapp.com
A list of public projects (I was kind of surprised there were so many): http://chiselapp.com/repositories/
I would be happy to use the site for publishing software. But to see if I can rely on the site for backup, aswell as simply general interest; I would enjoy reading (maybe a page on the site) about where it came from / what your plans are for it / longevity / intent
i.e. I want to hear more about you ;)