add multi-line comment support in api

[a1012112796]

first step of #12640

• add side and line to replace new/old_position in api like github

• add start_line in api like github for multi-line comment creating

• for multi-line comment, will cut all lines in range [start_line, line] for patch generate, then user can view all lines in this range on commnet list ui. example:
  

• not suport start_side now, line and start_line should in same side

todos:

• suport creating multi-line comments by ui & incomming mail
• more ui updates

[denyskon]

@a1012112796 Could you resolve conflicts?

[delvh]

I have architectural objections to this PR:
At the moment, you store StartLine (+/-) and Line (+/-) (let's ignore the confusing naming for now).
But with your approach, you must to store 4 lines: Start (old), End (old), Start (new), End (new).
Otherwise you confuse everyone trying to maintain the code, and create technical debt.

There is a reason why I recommended a one-way multiline comment that only stores a relative counter.
It is much easier to implement, and more user-friendly.
You don't need any convoluted mechanism to calculate which line is included in your drag, thus you make it predictable for your user, and as a user, you very rarely need a multiline comment both on the old side as well as the new side.

[a1012112796]

But with your approach, you must to store 4 lines: Start (old), End (old), Start (new), End (new).
Otherwise you confuse everyone trying to maintain the code, and create technical debt.

why need four lines? do you means in database? now only add two new colums named as start_line and is_multi_line, the end_line is line in db. and in fact start_line only will be used in patch generation step, which willn't break curent ui logic. or maybe show it on ui in future.

then, not support start_side and line in different sides now also, because it's hard to generate patch for this usage.

[anbraten]

I guess what delvh wants to say is that instead of adding start_line, you could add a next_lines property. In case next_lines is 0 it would just highlight the current line (as currently implemented). By using a number like next_lines>=1 it would hightlight the next x lines starting by line.