The Linux kernel adopted Bitkeeper before git and it never spread out from there. It's not that many people working on the kernel.

git growth was very symbiotic with GitHub growth. I don't remember why GitHub became popular in the first place. I think it was the Ruby community? GitHub was one of their own during an explosion of Ruby on Rails and successful startups using it.

Sure, if we ignore Bit keeper was commercial, always a hot topic, and not developed by Linus.

Yeah, for a while it was not clear that git would win over mercurial. GitHub was decisive.

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