Apply tab size preference to more places

[kidonng]

Description

#4833 is a good start but not perfect:

• Tab size adjustment won't work for regular code blocks (<pre>) in comments, once we drop the variable from :root
• File blocks in comments use a fixed tab size of 4 instead of following user preference
• Tab size adjustment doesn't work for editors

For the second and third points, maybe we can fetch user preference from https://github.com/settings/appearance#tab-size-heading (or look at DOM) and reference it in our code. We can use a long expire timeout since it should be a rarely-changed setting.

Tweaking the editors are just my thoughts though, it may not be trivial or worth the effort.

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A bit of context about editors:

• New file and new gist always uses Spaces with an indentation size of 2
• Editing files indented with Tabs will always use an indentation size of 8 (or 2 if there are no indentation for the editor to figure out)
• Editing files indented with Spaces will always inherit the indentation size of the file

Screenshot

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Example URL

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[fregante]

• Tab size adjustment won't work for regular code blocks (<pre>) in comments, once we drop the variable from :root
• File blocks in comments use a fixed tab size of 4 instead of following user preference

Fixed in #5715

• Tab size adjustment doesn't work for editors

If you still want this, open a new issue so it can be discussed and tracked specifically. As you mentioned:

it may not be trivial or worth the effort.