Fix text search on *nix (#824)

This regressed in #821.

Author: lhecker

crates/edit/src/bin/edit/documents.rs

@@ -282,6 +282,7 @@ impl DocumentManager {
         let buffer = TextBuffer::new_rc(false)?;
         {
             let mut tb = buffer.borrow_mut();
+            tb.set_insert_final_newline(!cfg!(windows)); // As mandated by POSIX.
             tb.set_margin_enabled(true);
             tb.set_line_highlight_enabled(true);
         }

crates/edit/src/buffer/mod.rs

@@ -316,7 +316,7 @@ impl TextBuffer {
             ruler: 0,
             encoding: "UTF-8",
             newlines_are_crlf: cfg!(windows), // Windows users want CRLF
-            insert_final_newline: !cfg!(windows), // As mandated by POSIX.
+            insert_final_newline: false, // NOTE: Even with POSIX, single-line buffers need this to be false
             overtype: false,
 
             wants_cursor_visibility: false,