Implement additional comments commands (open_comment_above, open_comment_below etc.)

[andreystepanov]

I find myself writing custom commands to add comment lines above/below current line, to easily document code i'm writing. Especially true for haddock style comments used in Haskell.

Currently i can achieve this with following configuration:

[keys.normal]
# Ctrl+Enter inserts Haskell comment below current line
C-ret = [ 
  "goto_line_end_newline", 
  ":append-output echo '-- '", 
  "insert_at_line_end" 
]

# Shift+Ctrl+Enter inserts Haskell comment above current line
S-C-ret = [ 
  "goto_line_start",
  ":insert-output echo '-- '",
  "insert_at_line_end" 
]

The problem with this approach is that i can't have single shortcut for all the languages i might write. In this case it will only work for languages with the comment-token = "--".

It would've been nice to have a dedicated commands that can insert/append new comment lines using comment-token defined in configuration of currently active language. All of this information is already available to the editor.

Suggested names might be:

• add_comment_line_above (similar to add_newline_above)
• add_comment_line_below (similar to add_newline_below)

But since it puts user in Insert Mode after execution, maybe would be better to use open_ prefix, similar to open_above/open_below commands.

• open_comment_above - opens new comment line above selection.
• open_comment_below - opens new comment line below selection.

Basic commands:

• insert_comment_token - inserts comment-token and 1 space before each selection (similar to :insert-output).
• append_comment_token - appends comment-token and 1 space after each selection (similar to :append-output).

insert_comment_token/append_comment_token might be a basis for other commands - which may cover other use-cases - such as commenting the rest of the line (everything after current cursor), or commenting just a part of the line (using block comments).

Having basic commands we then can also implement universal keybindings using following configuration (in this case there's no hard-coded comment-token's and it will work in any language):

[keys.normal]
# or just [ "open_comment_below" ]
C-ret = [ 
  "add_newline_below", 
  "move_line_down",
  "insert_comment_token" ,
  "insert_mode"
]

# or just [ "open_comment_above" ]
S-C-ret = [ 
  "add_newline_above",
  "move_line_up",
  "insert_comment_token" ,
  "insert_mode"
]

What do you think?