DocLineComparator performance issue

[mehmet-karaman]

Hello,

I identified a performance issue in the CompareEditor that occurs when comparing files with many similar lines. This typically affects files where most lines start identically but differ only toward the end, such as configuration files containing workspace-specific paths.

In these cases, the comparison currently spends a lot of time checking entire lines character by character, even though many differences could be detected much earlier. A simple preliminary check—verifying whether the first and last characters of a line match—can already rule out many unnecessary full comparisons.

I applied this optimization in the DocLineComparator, which significantly reduces the amount of work needed during comparison. For the affected scenarios, this change improves performance by approximately 80–90%.

I would like to provide a PR for this. Thanks in advance.

Best regards
Mehmet Karaman