Enable "smart case" for search

[roblourens]

"Smart case" is a ripgrep feature that will handle a query as case-sensitive if it contains uppercase characters, and case-insensitive if it doesn't.

For example, a document contains

asdf
asdF

With "smart case" enabled, the query asdf matches line 1 and line 2. And the query asdF only matches line 2.

It also works for regular expressions. The regex query asd\S matches line 1 and line 2. The query asd[A-Z] only matches line 2.

We should introduce a setting, search.smartCase or editor.find.smartCase. This is easy to hook up for ripgrep, but we also need to implement it for when results are provided by the editor, and for when ripgrep is not used. This is easy for non-regex queries. For regex queries, ripgrep previously attempted to tell whether the regex would match any uppercase characters. But this had unintended consequences, like \w triggering case-sensitivity, so now it only checks whether the regex text has any unescaped uppercase characters (BurntSushi/ripgrep#717). Fortunately this is easy for us to match.

• Does this make sense for editor find or just search?
• If both, is it a problem that search is respecting some editor.find settings but not all?

cc @rebornix

Alternately, the "case sensitive" toggle button could be a 3-mode switch which also can enable smart case.

[octref]

See #42684 for an issue.
I think this should go to editor find too. Vim has this on by default.
One thing would be great: When this setting is on, whenever you type in the first uppercase char it toggles the Match Case icon (but later people can still toggle it off).

[roblourens]

I agree, we had talked about more UI for that. Just filed #42687