Bah. Anybody can clone a git repo. It's trivial to move off of github with a git repo if they want, or possible to migrate to another database if they want to go through the disruption.
Going to git is about gaining developer mindshare. There are more people using git now. So being on git will bring in more "drive by pr's". I know for my part, life is too short to keep current on multiple source code control tools. I've done plenty in my time, but git is where I'm at now. I use git now at work, and until now, all of the hobby projects that interested me except for 1, were on git. Now all are on git.
At PyCon 2016 Guido told the story of how Mercurial was selected over git. It seemed like an even match at the time. Guido is very source-code-control-tool-agnostic. But git is the current best path to enabling more people to help with cpython development.
It is hardly trivial to move off. Bugs would have to be migrated, links updated, documentation, automated build systems, workflow as well as user remapping.
While not being Mercurial is one thing it is really more about being on GitHub that is the problem. Kings will get complacent (remember how long it took to GitHub to add some features).
I also vaguely remember the github guys trashing Mercurial with arguabley a propaganda campaign (something "git is better than X"). All that content is missing now but I do remember (I'll have to look on way back machine later).
Going to git is about gaining developer mindshare. There are more people using git now. So being on git will bring in more "drive by pr's". I know for my part, life is too short to keep current on multiple source code control tools. I've done plenty in my time, but git is where I'm at now. I use git now at work, and until now, all of the hobby projects that interested me except for 1, were on git. Now all are on git.
At PyCon 2016 Guido told the story of how Mercurial was selected over git. It seemed like an even match at the time. Guido is very source-code-control-tool-agnostic. But git is the current best path to enabling more people to help with cpython development.