Add info on how to checkout earlier versions pre-GitHub migrations

[Mariatta]

It would be great if Git Bootcamp has information on how to checkout git tags to get the earlier CPython releases (e.g. 3.3, 3.4 )

3.3. and 3.4 aren't on CPython's GitHub as branches (unlike 3.7, 3.8, etc), but there are git tags, can can be checked out as follows:

# list all git tags matching v.3.3
git tag -l 'v3.3*'

# checkout the v.3.3.0 tag to a local branch
git checkout tags/v.3.3.0 -b my-own-3.3.0-branch

[ned-deily]

It's a bit simpler than that. You don't need to specify tags/ when referencing tags.

git checkout v3.3.0           # for detached head state
git checkout v3.3.0 -b v3.3.0 # to also create a local branch

https://git-scm.com/book/en/v2/Git-Basics-Tagging

[zware]

We've also kept tags for old branches with the same name as the branch (for example, 3.2, 3.3, etc.), though that tag doesn't seem to have been created for 3.4 it seems an explicit git fetch --tags upstream may be necessary to get them all. With those tags, there's no difference to checking out an active branch, with the exception that you'll be on a "detached HEAD" if you don't create your own branch.