IStringLocalizer.GetAllStrings should support an arg to specify culture walk behavior

[DamianEdwards]

Depends on #18

Currently, IStringLocalizer.GetAllStrings will return the union of all strings for the current culture and all ancestors of the current culture. E.g. if the current culture is "en-US" and it contains a single string "Hello", and the culture "en" contains a single string "Goodbyte", the call to IStringLocalizer.GetAllStrings for "en-US" will return both the "Hello" and "Goodbye" strings.

This behavior may not always be desirable (e.g. it differs to how ResourceManager.GetResourceSet works). As such, we should support a way to specify the behavior during the call, e.g. GetAllStrings(includeAncestorCultures: false);

The default behavior should still be to include strings from ancestor cultures.

[DamianEdwards]

Interested in your thoughts @davidfowl @muratg @Eilon @lodejard

[muratg]

I like it.

[glen-84]

So if you have "colour" in "en", and nothing in "en-US", the translation for "en-US" would be "colour", which is not correct until such time as you "override" it as "color" in "en-US"? Perhaps it should be off by default to avoid unexpected behaviour?

(sorry, I know public feedback was not requested 😨)