Rename master to main

[cpcloud]

Seems like folks are expecting main to be the default everywhere now. Let's follow suit and rename our default branch to main.

@jreback Thoughts?

[cpcloud]

Doesn't seem to be much traction here. Closing for now.

[lostmygithubaccount]

should we make this change? particularly as ibis-substrait, ibisml, ibis-birdbrain, and any future projects in the org will default to main. any reason not to switch over at this point? GitHub should do a decent job at redirects and everything

[saulpw]

I vote no. Any future projects can default to main but it's not worth one iota of friction to instigate a change like this that has no value and that no one asked for.

[lostmygithubaccount]

The value to me is in consistency and cognitive overhead -- while it's not a lot, I do have bash aliases that are hardcoded to master or main and I'd like to not deal with the differences (I recognize I could work around this, but Ibis is the last repo I regularly touch that uses master)

also from a new contributor or just casual user perspective, it's confusing for every other repo (Ibis Substrait, IbisML, Ibis Birdbrain, governance) to have a different default branch name

[gforsyth]

I'm in favor of the rename, also for general consistency and alias ergonomics.
AND it might be gnarly getting all the CI jobs updated accurately, so whomever wants to champion this should get ready for some YAMLgineering.

[NickCrews]

I'm +1 to rename