REPL auto-indentation is wrong with comments

[HarryLHW]

Bug report

Bug description:

Currently, the REPL auto indentation is like this:

The correct one should be:

I am working on a PR to fix this.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-122237: Fix REPL wrong auto-indentation with comments #122238
• gh-122237: Fix repl auto indentation wrong with comments #122383

[HarryLHW]

This is also incorrect when "#" happens to be the last non-whitespace character.

[Wulian233]

Another #124096

[ambv]

That was fixed in GH-123196.