There isn't even a way to opt-out, why do people jam shit like this onto their user's throats?
Yes it's politically correct but adding "git branch -M main" on every new repo the mankind creates is just a waste of goddamn bytes and kills a penguin every year for every extra cpu cycle it wastes.
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Edit:
Nevermind, turns out you can skip that "git branch -M main" step. I'm a fucking idiot I guess.
If you really want to use an environmental argument it's very likely that using a branch name that's 2 characters shorter on every merge to the main/master branch, every list of branches, every Github page that displays the main/master branch name, etc will save a far greater amount of energy than renaming repos will ever use. On a random repo homepage the word 'master' appears 31 times in the HTML content, so switching to 'main' would reduce the bandwidth on every single page load by 62 characters[1].
Any repo that opts out must be run by a climate change denier.
[1] Compression has been ignored to protect the argument.
It's easy to change and it's nice that old branch histories will do directs to new branch.
This stuff always gets sidelined into trivialities that are insulting to people who do, in fact, face injustice.