Problem:
A text edit positioned entirely past the last buffer line, with
newText ending in a newline, leaves a stray blank line: the
past-the-end path appends the trailing empty fragment produced by
vim.split() and does not set has_eol_text_edit, so the end-of-buffer
cleanup is skipped. Formatting servers emit such edits whenever
formatting moves text to the end of a document.
Regression from ec94014cd1 (#20137), which split the past-the-end
fast path off the clamp path that sets the flag.
Solution:
Set has_eol_text_edit in the past-the-end path, like the adjacent
path that clamps end_row.
d42f7ee9dc