Description

Fixes: #13159

After the change, std help will no-longer print out "double error" messages.

Actually I think it's tricky to make it right. To make help <cmd> keeps paging feature from fallback man command. I have to split commands into scope-commands and external-commands.

If we don't split it, simply call let commands = (try { commands $target_item --find $find }) in help main will cause us to lost paging feature, which is not we want.

A comment from original issue:

If there are no objections, I'd like to remove the man page fallback code from std help for the moment. While it's probably fixable, it's also platform specific and requires testing on all platforms. It also seems like a low-value add here.

Actually I think it's a beautiful feature of std help, so I want to keep it here.

User-Facing Changes

Before

> help commands asdfadsf
Help pages from external command asdfadsf:
No manual entry for asdfadsf
Error:   × std::help::command_not_found
   ╭─[entry #11:1:15]
 1 │ help commands asdfadsf
   ·               ────┬───
   ·                   ╰── command not found
   ╰────

After

> help commands asdfasdf
Help pages from external command asdfasdf:
No manual entry for asdfasdf

Tests + Formatting

Actually it's a little hard to add test because it required user input (especially for fallback man command)