Fix E94 on selecting a file when there is only one help window

[mnishz]

Summary

Fix E94 on selecting a file when there is only one help window.

How to recreate

1. vim -c 'help | only'
2. :CtrlPMRUFiles or another CtrlP command
3. Select any file
4. E94 occurs

Cause

#444 has changed the behavior when the current buffer type is 'help' so that s:openfile() would always use 'b' command. This works well for :CtrlPBufTag, but doesn't work for other commands like :CtrlPMRUFiles.

let cmd =
  \ md == 't' || s:splitwin == 1 ? ( useb ? 'tab sb' : 'tabe' ) :
  \ md == 'h' || s:splitwin == 2 ? ( useb ? 'sb' : 'new' ) :
  \ md == 'v' || s:splitwin == 3 ? ( useb ? 'vert sb' : 'vne' ) :
  \ &bt == 'help' ? 'b' :
  \ call('ctrlp#normcmd', useb ? ['b', 'bo vert sb'] : ['e'])

Fix

Use 'b' only if the current buffer type is 'help' and the opening file is the help file itself. Otherwise, use ctrlp#normcmd() function as before. (ctrlp#normcmd() looks for a available normal window to open the file and assumes that a window for 'help' is not available, so, #444 (#437) occurs.)

I also found that md == 't' <c-t>, md == 'h' <c-x> and md == 'v' <c-v> doesn't work for :CtrlPBufTag. So I created l:openmyself to set l:useb correctly.

Validation

• E94
  • E94 occurs without the patch with the above sequence.
  • E94 doesn't occur with the patch with the above sequence.
• [Bug] CtrlPBufTag did not work for vim help file #437
  • [Bug] CtrlPBufTag did not work for vim help file #437 doesn't occur without the patch.
  • [Bug] CtrlPBufTag did not work for vim help file #437 doesn't occur with the patch.
• Other opening methods (<c-t>, <c-x> and <c-v>)
  • Other opening methods doesn't work for :CtrlPBufTag without the patch.
  • Other opening methods work well for :CtrlPBufTag with the patch.

[mattn]

Thank you

[mnishz]

Thank you for merging!