Vendor dependencies

Let's see how I like this workflow.

vendor/tui/tests/backend_termion.rs

@@ -0,0 +1,63 @@
+#[cfg(feature = "termion")]
+#[test]
+fn backend_termion_should_only_write_diffs() -> Result<(), Box<dyn std::error::Error>> {
+    use std::{fmt::Write, io::Cursor};
+
+    let mut bytes = Vec::new();
+    let mut stdout = Cursor::new(&mut bytes);
+    {
+        use tui::{
+            backend::TermionBackend, layout::Rect, widgets::Paragraph, Terminal, TerminalOptions,
+            Viewport,
+        };
+        let backend = TermionBackend::new(&mut stdout);
+        let area = Rect::new(0, 0, 3, 1);
+        let mut terminal = Terminal::with_options(
+            backend,
+            TerminalOptions {
+                viewport: Viewport::fixed(area),
+            },
+        )?;
+        terminal.draw(|f| {
+            f.render_widget(Paragraph::new("a"), area);
+        })?;
+        terminal.draw(|f| {
+            f.render_widget(Paragraph::new("ab"), area);
+        })?;
+        terminal.draw(|f| {
+            f.render_widget(Paragraph::new("abc"), area);
+        })?;
+    }
+
+    let expected = {
+        use termion::{color, cursor, style};
+        let mut s = String::new();
+        // First draw
+        write!(s, "{}", cursor::Goto(1, 1))?;
+        s.push('a');
+        write!(s, "{}", color::Fg(color::Reset))?;
+        write!(s, "{}", color::Bg(color::Reset))?;
+        write!(s, "{}", style::Reset)?;
+        write!(s, "{}", cursor::Hide)?;
+        // Second draw
+        write!(s, "{}", cursor::Goto(2, 1))?;
+        s.push('b');
+        write!(s, "{}", color::Fg(color::Reset))?;
+        write!(s, "{}", color::Bg(color::Reset))?;
+        write!(s, "{}", style::Reset)?;
+        write!(s, "{}", cursor::Hide)?;
+        // Third draw
+        write!(s, "{}", cursor::Goto(3, 1))?;
+        s.push('c');
+        write!(s, "{}", color::Fg(color::Reset))?;
+        write!(s, "{}", color::Bg(color::Reset))?;
+        write!(s, "{}", style::Reset)?;
+        write!(s, "{}", cursor::Hide)?;
+        // Terminal drop
+        write!(s, "{}", cursor::Show)?;
+        s
+    };
+    assert_eq!(std::str::from_utf8(&bytes)?, expected);
+
+    Ok(())
+}