Merge two multiline strings like git does

Question

I'd like to 'combine' two (usually very similar) multiline strings (close to, what git does, when it merges changes on files).

Something like

>>> combine([
    'Hello,',
    'this is a text hat has been altered on one place',
    'while altered differently on another',],[
    'Hello,',
    'this is another text hat has been altered on a different place',
    'while altered differently on another',])
['Hello,',
 'this is another text hat has been altered on a different place',
 'this is a text hat has been altered on one place',
 'while altered differently on another',]

I don't have enough information for a three-way-diff so I'd like to find similarities and make sure no lines get lost.

I found several manual approaches using set and so on. But I need a way to keep order , similar sections and multiple occurrences of identical (ie empty) lines.

Is there a 'pythonic' (short, elegant, sophisticated) way to do this?

Answer 1

If you have two elements only(lists), this should work:

def combine(target):
  return target[0]+list(x for x in target[1] if x not in target[0])

This adds the first item with elements that are in the second item but not in the first.

Later edit:

I haven't used difflib a lot, but it gives the correct result for me.

import difflib

def merge_text(text1:str, text2:str) -> str:
    return "\n".join(
        line[2:] for line in difflib.Differ().compare(
            text1.split("\n"),
            text2.split("\n")) 
        if not line.startswith("?"))