perf: replace startsWith with charAt

[btea]

What is the purpose of this pull request?

refer

fast-glob/src/utils/path.ts

Lines 32 to 33 in 1e520c1

	// We do not use `startsWith` because this is 10x slower than current implementation for some cases.
	// eslint-disable-next-line @typescript-eslint/prefer-string-starts-ends-with

What changes did you make? (Give an overview)

…

[mrmlnc]

Thanks for the pull request.

I think I would prefer to keep the linter rule and continue using the .startsWith method instead of the .charAt method in most cases.

The difference between the place you indicated in the pull request and the others is that it is a very hot. The removeLeadingDotSegment method is called for each found entity. For real directories, it can be tens of thousands of calls. The performance of such methods needs to be improved.

In other methods (like the ones you changed in this pull request), the frequency of calls is much, much lower. For patterns, we can talk about dozens of calls, no more. At worst, it could be hundreds of calls if the user specifies hundreds of patterns. But I think he will run into another performance problem like pattern matching.

Thank you for your pull request. If you are aware of any cases where your changes have led to a noticeable improvement in speed, please let me know.

[btea]

Thanks for the detailed instructions.