It isn't shipped on macOS, and the Homebrew version of Git has it packaged separately.
I fired it up on a Git export of a Fossil repo here, and it's missing features of Fossil's web UI timeline view:
1. Cherrypick markers
2. Diff arbitrary versions (it shows only diff from previous)
3. Branch coloring
4. Hyperlinks to produce new timeline views: click author to get list of commits by that author, click timestamp to get a new timeline surrounding that point in time, etc....
5. Integration with other web UI features. For instance, you can create a Fossil wiki article attached to a commit from Fossil UI, but you can't attach a GitHub wiki article to a Git commit from gitk.
For another, Fossil has a feature to produce zip and tarball downloads of particular versions, which have links in the commit info page, which means visitors to your project don't need to clone the whole thing and roll it back to that version manually to get a single version. That's integrated into the Fossil web UI timeline: click a version, click Zip, done.
6. A modern browser fits its platform and offers more UI affordances than the mid-1990s Motif-inspired Tk. (Better copy/paste behavior, font rendering, zooming, native controls, etc.) Web UIs get a lot of angst these days, but like them or not, they're native citizens of the host platform these days in a way that Tk is not.
> It isn't shipped on macOS, and the Homebrew version of Git has it packaged separately.
That's a bit like saying python doesn't ship with a GUI because ubuntu split tkinter out; projects can't control what downstream does, and the complaint from the article was that they didn't want a second dependency; gitk is part of the git project so it's a single dependency just as much as relying on fast-import would be.
Yes, I suspect fossil's timeline is better than gitk, particularly since gitk has changed almost not at all in the past decade. However the complaint was not that gitk was worse than timeline, it was that there was no tool even slightly like it in git (and then the github "network graph" was not part of git, and worse than the Fossil timeline; that particular point makes me think gitk was never considered).
As a side note, #3 isn't possible in git because commits don't belong to branches, but that's addressed in a different point from the article in question.
