PR: Update contributing, release and maintenance instructions for backporting

[ccordoba12]

Description of Changes

This not only simplifies our workflow by avoiding the need to manually forward-port PRs from the stable branch to master. It'll also help us to maintain a more stable branch, by only backporting what we think is really necessary.

Issue(s) Resolved

Fixes #

Affirmation

By submitting this Pull Request or typing my (user)name below,
I affirm the Developer Certificate of Origin
with respect to all commits and content included in this PR,
and understand I am releasing the same under Spyder's MIT (Expat) license.

I certify the above statement is true and correct: @ccordoba12

[ccordoba12]

@dalthviz, this is ready for review.

[dalthviz]

Give a quick check and makes sense to me 👍 Left only a single comment related with the management of the alpha part over the version update. Also, thinking about docs updates. Could this PR be a good place to update the README badges that launch binder instances?

Not sure if there are other places where 5.x is still being mentioned 🤔

[ccordoba12]

Could this PR be a good place to update the README badges that launch binder instances?

I'll leave that for another PR to include a critical fix to avoid hard freezes on Binder.

[dalthviz]

Thanks @ccordoba12 ! LGTM 👍 Following the updated steps, after this gets merged, this should be backported to 6.x, right?

Also, is there any other change you want to add here or should I proceed with the merge?

[ccordoba12]

Following the updated steps, after this gets merged, this should be backported to 6.x, right?

Correct. If a PR is marked for 6.0.x, 6.1.x, etc, it needs to be backported.

Also, is there any other change you want to add here or should I proceed with the merge?

Nop, this is ready.

By the way, I'm using regular merges in master to preserve the commit history, but squash merges in 6.x because history is not so critical there. And I'm planning to add another bot to automatically do that in 6.x.

[dalthviz]

@meeseeksdev please backport to 6.x

[dalthviz]

By the way, I'm using regular merges in master to preserve the commit history, but squash merges in 6.x because history is not so critical there. And I'm planning to add another bot to automatically do that in 6.x.

Is there a case where you will need to merge something directly to 6.x without passing from master and the backporting procedure (which seems like creates a PR with a single commit)?

[ccordoba12]

Is there a case where you will need to merge something directly to 6.x without passing from master and the backporting procedure (which seems like creates a PR with a single commit)?

There should be very few things that only apply to 6.x. For instance, I made PR #22468 to fix its dev version because that couldn't be backported (PR #22465 was the equivalent for master).