describe purpose of the branches master and 4.x

[niccokunzmann]

@mauritsvanrees @geier
I created this PR to make the purpose of the branches clear.
There is some difference between the branch purpose as pointed out in #360:

Increase master branch version to 5 (or 6 if needed). This should keep working on Plone 6.0 (which is near beta), which means Python 3.7-3.10.

and this PR #366

Require Python 3.8.

How to approach this?

[geier]

To me it sounds good, icalendar 4.x on 3.7-3.10, icalendar >= 5.0 on python >= 3.8

[geier]

Thinking about this again:

Perhaps we should make a 5.x release (or at least a branch for now) specifically for Plone 6 with Python 3.7-3.10 support. This will be much easier to support then the 4.x branch, which still has Python 2 and Python 3.4-3.6 support.

Perhaps even hold out on dropping 3.7 support until it is really needed.

[mauritsvanrees]

In this discussion comment I wrote:

For me it is okay to drop Python 2.7 and 3.7 from the master branch. I have changed Plone 5.2 to use branch 4.x. And on latest Plone 6.0 I have added a pin for Python 3.7 to use the latest 4.x version as well.

I dropped 3.7 because of what @geier wrote:

I'd like to not only drop python 3.6 but also 3.7 (because python 3.8 makes type hinting really a lot easier IMHO)

In the spirit of moving forward, this would be good. But I am not well versed in type hinting yet. And since this has been dubbed as a critical project, perhaps we should not abandon older Python versions until they are really not supported anymore.
From a Plone standpoint, it should be fine to drop 3.7. I am happy to let you two decide on this.

[niccokunzmann]

How is it if we support 3.7 for a bit and if we see a merge request failing because of 3.7 incompatibility, we drop 3.7 explicitely?
Since @mauritsvanrees approved, @geier - I see your input on that:

Perhaps even hold out on dropping 3.7 support until it is really needed. - @geier

I will make the changes in the documentation.

[coveralls]

Pull Request Test Coverage Report for Build 2863350733

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 90.773%

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Totals
Change from base Build 2854913909:	0.2%
Covered Lines:	1151
Relevant Lines:	1268

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💛 - Coveralls

[niccokunzmann]

This mentions 3.7+ now.

[niccokunzmann]

I like documentation! It allows us to have a hands-on discussion and join forces into one direction :)

[niccokunzmann]

@geier - if you are fine with these changes, I think, it is up to you to merge them. Then, it is clear how to maintain the repository and how to direct contributions. (branch + version) I'd be ok with both 3.8+ and 3.7+. Also, I think we have enough time to migrate to 3.8 and zoneinfo - 10 months - when we merge it with 3.7+.

[niccokunzmann]

We merged #366 and thus the changes here do not reflect what is written - but I do documentation first - the documentation guides the expectation and the expectation the code. I will make changes for 3.7 based on #366 once it is merged.

[mauritsvanrees]

LGTM now.

[geier]

Sorry about doing a u-turn there @mauritsvanrees .

Didn't see that you had already dropped 3.7. I don't mind either way.

[niccokunzmann]

@geier

Who would you like to review?

I see this:

I think mauritsvanrees gave a review and I made the commit and I do not know who else is left to review/take the decision.
You can merge from my perspective. We can drop 3.7 any time but add it in will be hard, maybe.

Like, I really mean it as a question: Who would you like to review?

[geier]

I actually wanted to review, self assigned but then got interrupted... I'll merge this now.