vim-patch:9.1.0743: diff mode does not handle overlapping diffs correctly (#30532)

Problem:  diff mode does not handle overlapping diffs correctly
Solution: correct the logic to handle overlapping blocks
          (Yukihiro Nakadaira)

Vim merges overlapped diff blocks and it doesn't work expectedly
in some situation.

closes: vim/vim#15735

https://github.com/vim/vim/commit/06fe70c183a53ea97cd42ace490d4fb9fd14f042

Co-authored-by: Yukihiro Nakadaira <yukihiro.nakadaira@gmail.com>

1 files changed, 539 insertions, 0 deletions

diff --git a/test/functional/ui/diff_spec.lua b/test/functional/ui/diff_spec.lua
index 8db6f776d1..d6a04f90f6 100644
--- a/test/functional/ui/diff_spec.lua
+++ b/test/functional/ui/diff_spec.lua
@@ -12,6 +12,19 @@ local exec = n.exec
 local eq = t.eq
 local api = n.api
 
+local function WriteDiffFiles(text1, text2)
+  write_file('Xdifile1', text1)
+  write_file('Xdifile2', text2)
+  command('checktime')
+end
+
+local function WriteDiffFiles3(text1, text2, text3)
+  write_file('Xdifile1', text1)
+  write_file('Xdifile2', text2)
+  write_file('Xdifile3', text3)
+  command('checktime')
+end
+
 before_each(clear)
 
 describe('Diff mode screen', function()
@@ -1515,3 +1528,529 @@ it("diff mode draws 'breakindent' correctly after filler lines", function()
                                                  |
   ]])
 end)
+
+-- oldtest: Test_diff_overlapped_diff_blocks_will_be_merged()
+it('diff mode overlapped diff blocks will be merged', function()
+  write_file('Xdifile1', '')
+  write_file('Xdifile2', '')
+  write_file('Xdifile3', '')
+
+  finally(function()
+    os.remove('Xdifile1')
+    os.remove('Xdifile2')
+    os.remove('Xdifile3')
+    os.remove('Xdiin1')
+    os.remove('Xdinew1')
+    os.remove('Xdiout1')
+    os.remove('Xdiin2')
+    os.remove('Xdinew2')
+    os.remove('Xdiout2')
+  end)
+
+  exec([[
+    func DiffExprStub()
+      let txt_in = readfile(v:fname_in)
+      let txt_new = readfile(v:fname_new)
+      if txt_in == ["line1"] && txt_new == ["line2"]
+        call writefile(["1c1"], v:fname_out)
+      elseif txt_in == readfile("Xdiin1") && txt_new == readfile("Xdinew1")
+        call writefile(readfile("Xdiout1"), v:fname_out)
+      elseif txt_in == readfile("Xdiin2") && txt_new == readfile("Xdinew2")
+        call writefile(readfile("Xdiout2"), v:fname_out)
+      endif
+    endfunc
+  ]])
+
+  local screen = Screen.new(35, 20)
+  screen:attach()
+  command('set winwidth=10 diffopt=filler,internal')
+
+  command('args Xdifile1 Xdifile2 | vert all | windo diffthis')
+
+  WriteDiffFiles('a\nb', 'x\nx')
+  write_file('Xdiin1', 'a\nb')
+  write_file('Xdinew1', 'x\nx')
+  write_file('Xdiout1', '1c1\n2c2')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:              }│{7:  }{27:^x}{4:              }|
+    {7:  }{27:b}{4:              }│{7:  }{27:x}{4:              }|
+    {1:~                }│{1:~                }|*16
+    {2:Xdifile1          }{3:Xdifile2         }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles('a\nb\nc', 'x\nc')
+  write_file('Xdiin1', 'a\nb\nc')
+  write_file('Xdinew1', 'x\nc')
+  write_file('Xdiout1', '1c1\n2c1')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:              }│{7:  }{27:^x}{4:              }|
+    {7:  }{22:b              }│{7:  }{23:---------------}|
+    {7:  }c              │{7:  }c              |
+    {1:~                }│{1:~                }|*15
+    {2:Xdifile1          }{3:Xdifile2         }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles('a\nc', 'x\nx\nc')
+  write_file('Xdiin1', 'a\nc')
+  write_file('Xdinew1', 'x\nx\nc')
+  write_file('Xdiout1', '1c1\n1a2')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:              }│{7:  }{27:^x}{4:              }|
+    {7:  }{23:---------------}│{7:  }{22:x              }|
+    {7:  }c              │{7:  }c              |
+    {1:~                }│{1:~                }|*15
+    {2:Xdifile1          }{3:Xdifile2         }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  command('args Xdifile1 Xdifile2 Xdifile3 | vert all | windo diffthis')
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'y\nb\nc')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\ny\nc')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\nb\ny')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'y\ny\nc')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\ny\ny')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'y\ny\ny')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nx', 'y\ny\nc')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:c}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'x\nx\nc', 'a\ny\ny')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:^a}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'y\ny\ny\nd\ne')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:d}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'y\ny\ny\ny\ne')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'y\ny\ny\ny\ny')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:e}{4:        }│{7:  }{27:e}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\ny\ny\nd\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:d}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\ny\ny\ny\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\ny\ny\ny\ny')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:e}{4:        }│{7:  }{27:e}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb\ny\nd\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:d}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb\ny\ny\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb\ny\ny\ny')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:e}{4:        }│{7:  }{27:e}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb', 'x\nb', 'y\ny')
+  write_file('Xdiin1', 'a\nb')
+  write_file('Xdinew1', 'x\nb')
+  write_file('Xdiout1', '1c1')
+  write_file('Xdiin2', 'a\nb')
+  write_file('Xdinew2', 'y\ny')
+  write_file('Xdiout2', '1c1\n2c2')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:b}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*16
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles3('a\nb\nc\nd', 'x\nb\nx\nd', 'y\ny\nc\nd')
+  write_file('Xdiin1', 'a\nb\nc\nd')
+  write_file('Xdinew1', 'x\nb\nx\nd')
+  write_file('Xdiout1', '1c1\n3c3')
+  write_file('Xdiin2', 'a\nb\nc\nd')
+  write_file('Xdinew2', 'y\ny\nc\nd')
+  write_file('Xdiout2', '1c1\n2c2')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:b}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:c}{4:        }|
+    {7:  }d        │{7:  }d        │{7:  }d        |
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles3('a\nb\nc\nd', 'x\nb\nx\nd', 'y\ny\ny\nd')
+  write_file('Xdiin1', 'a\nb\nc\nd')
+  write_file('Xdinew1', 'x\nb\nx\nd')
+  write_file('Xdiout1', '1c1\n3c3')
+  write_file('Xdiin2', 'a\nb\nc\nd')
+  write_file('Xdinew2', 'y\ny\ny\nd')
+  write_file('Xdiout2', '1c1\n2,3c2,3')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:b}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }d        │{7:  }d        │{7:  }d        |
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles3('a\nb\nc\nd', 'x\nb\nx\nd', 'y\ny\ny\ny')
+  write_file('Xdiin1', 'a\nb\nc\nd')
+  write_file('Xdinew1', 'x\nb\nx\nd')
+  write_file('Xdiout1', '1c1\n3c3')
+  write_file('Xdiin2', 'a\nb\nc\nd')
+  write_file('Xdinew2', 'y\ny\ny\ny')
+  write_file('Xdiout2', '1c1\n2,4c2,4')
+  command('set diffexpr=DiffExprStub()')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:^y}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:b}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:d}{4:        }│{7:  }{27:y}{4:        }|
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+  command('set diffexpr&')
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'b\nc')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^b}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'c')
+  screen:expect([[
+    {7:  }{4:a        }│{7:  }{4:a        }│{7:  }{23:---------}|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }c        │{7:  }c        │{7:  }^c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', '')
+  screen:expect([[
+    {7:  }{4:a        }│{7:  }{4:a        }│{7:  }{23:---------}|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {1:~          }│{1:~          }│{7:  }^         |
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\nc')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'b')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^b}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {1:~          }│{1:~          }│{1:~          }|*15
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'd\ne')
+  screen:expect([[
+    {7:  }{27:a}{4:        }│{7:  }{27:a}{4:        }│{7:  }{27:^d}{4:        }|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'e')
+  screen:expect([[
+    {7:  }{4:a        }│{7:  }{4:a        }│{7:  }{23:---------}|
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }^e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nd\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:d}{4:        }|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:e        }│{7:  }{4:e        }│{7:  }{23:---------}|
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb\nd\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{27:c}{4:        }│{7:  }{27:c}{4:        }│{7:  }{27:d}{4:        }|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb\ne')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }e        │{7:  }e        │{7:  }e        |
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc\nd\ne', 'a\nx\nc\nx\ne', 'a\nb')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{4:c        }│{7:  }{4:c        }│{7:  }{23:---------}|
+    {7:  }{27:d}{4:        }│{7:  }{27:x}{4:        }│{7:  }{23:---------}|
+    {7:  }{4:e        }│{7:  }{4:e        }│{7:  }{23:---------}|
+    {1:~          }│{1:~          }│{1:~          }|*13
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\ny\nb\nc')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:y}{4:        }|
+    {7:  }{23:---------}│{7:  }{23:---------}│{7:  }{22:b        }|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+
+  WriteDiffFiles3('a\nb\nc', 'a\nx\nc', 'a\nb\ny\nc')
+  screen:expect([[
+    {7:  }a        │{7:  }a        │{7:  }^a        |
+    {7:  }{27:b}{4:        }│{7:  }{27:x}{4:        }│{7:  }{27:b}{4:        }|
+    {7:  }{23:---------}│{7:  }{23:---------}│{7:  }{22:y        }|
+    {7:  }c        │{7:  }c        │{7:  }c        |
+    {1:~          }│{1:~          }│{1:~          }|*14
+    {2:Xdifile1    Xdifile2    }{3:Xdifile3   }|
+                                       |
+  ]])
+end)