[locale] Extend cs locale with name of the months in genitive

[saxicek]

In Czech, it is possible to use also declined form of the month name instead of the nominative case.
This commit adds those declined names of the months.

@radekdostal @marxsk @petrbela - please verify this patch as locales have to be verified by native speakers.

This PR is meant to replace solution suggested in #4765 (and agreed with @marxsk in #4765 (comment))

Discussion:
Pro of this solution is that is it easier to understand because plain regexes or their arrays are used instead of anonymous function.
Con is that "červenec" must precede "červen" in the monthsRegex and monthsStrictRegex to match properly.

[jsf-clabot]

All committers have signed the CLA.

[coveralls]

Coverage increased (+0.003%) to 88.138% when pulling c225a7a on saxicek:patch-1 into c68b4f1 on moment:develop.

[saxicek]

Travis failed on locale/ka.js - which was untouched by this PR.

[petrbela]

I haven't kept up with how monthsStrict works these days. Is the inflected version automatically used after an ord date (like "1. cervna")?

I feel like we should add a test case for the format function (is it the LL format?), or whichever publicly available interface this change affects.

Con is that "červenec" must precede "červen" in the monthsRegex and monthsStrictRegex to match properly.

I'm okay with this as long as we add a comment to the source file why this workaround is necessary.

[saxicek]

@petrbela This change affects date parsing, not formatting. Therefore not sure about your suggestion to add test case for the format function.

Addressed the request to document why months are not in order in the regular expressions.

Unfortunately tests are still failing due to #4762.

[petrbela]

Ah right makes sense. I'm just wondering whether the functionality should be symmetric; if we can parse a specific format, we should be able to print (format) it, too. As far as I can see, that's not available right now. What do you think?

[saxicek]

Yes, it does make sense. But unfortunately I am unable to dedicate more time to design and implement this. Any volunteers?

[marxsk]

imho the impact of having function symmetric is not that big. Additionally, it makes sense to make this available also for the other languages. And it is possible that in various languages this 'genitive-case' is oversimplifaction.

[saxicek]

The thing I don't know is how would you switch between the 2 forms - new setting? Where? On the other hand if someone needs that then (s)he can just simply overload locale definition using:

moment.updateLocale('cs', {
    months : 'ledna_února_března_dubna_května_června_července_srpna_září_října_listopadu_prosince'.split('_')
});

You could also introduce new locale variant but still - I don't think it is worth the effort.

[marwahaha]

@saxicek what's the status of this? looks like you have approval. Also, are there changes that break existing users of this locale?

[saxicek]

Yes. I think those involved in the discussion are ok with the solution. We were waiting for #4762 to pass CI tests.