docs: correct watching dot files

[sfiquet]

Summary

The current config documentation states that the watcher ignores dot files and folders by default. This behaviour was changed by PR #10075 back in 2020.

As a user of Nextjs, I noticed that running the dev server concurrently with jest --watch caused Jest to constantly rerun all the tests when no source file had changed. This was due to the dev server writing to folder /.next, with the Jest watcher enthusiastically kicking in. The incorrect documentation made much harder to find the origin of the problem.

Test plan

This is purely documentation, limited to the paragraph about dotfiles watching in section watchPathIgnorePatterns.

[codecov-commenter]

Codecov Report

Merging #12161 (4234e79) into main (e835fae) will not change coverage.
The diff coverage is n/a.

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##             main   #12161   +/-   ##
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  Coverage   67.72%   67.72%           
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  Files         328      328           
  Lines       16993    16993           
  Branches     4818     4818           
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  Hits        11508    11508           
  Misses       5452     5452           
  Partials       33       33           

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[SimenB]

thanks! Could you update the versioned docs this applies to as well? (meaning in docs/, 26.x and all of 27, I guess?)

[sfiquet]

I'm on it!

Since the change in behaviour happened in version 26.2.0, the doc for 26.x should probably describe the behaviour before and after the change, right?

Also, do I need to add an item in the changelog or is this too trivial?

[SimenB]

The way the 26.x ocs work is that they capture the latest release of that major, so just after is fine 🙂

Also, do I need to add an item in the changelog or is this too trivial?

Not needed as it won't be part of any code that's released 👍

[sfiquet]

I think I should clarify that version control folders are ignored or it might cause unnecessary concern. What do you think of this alternative wording?

Even if nothing is specified here, the watcher will ignore changes to the version control folders (.git, .hg). Other hidden files and directories, i.e. those that begin with a dot (.), are watched by default. Remember to escape the dot when you add them to watchPathIgnorePatterns as it is a special RegExp character.

[SimenB]

Yeah, that sounds good. Thanks!

[SimenB]

Prettier is unhappy, mind running it?

[sfiquet]

Sorry about that. I didn't realise it was necessary for documentation.

[SimenB]

No worries! 😀

[SimenB]

looks great, thanks!

[github-actions]

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