Explicitely support tmux, fallback if terminfo isn't available (#9)

CHANGELOG.md

@@ -6,6 +6,8 @@
 - Update dependencies.
 - Update to nix 0.26.
 - Change MSRV policy to stable-5 supported, and bump MSRV to 1.60.0.
+- Handle tmux explicitly ([#9](https://github.com/watchexec/clearscreen/pull/9)).
+- Fall back to hardcoded sequence if terminfo is not available ([#9](https://github.com/watchexec/clearscreen/pull/9)).
 
 ## v1.0.10 (2022-06-01)
 

TERMINALS.md

@@ -72,6 +72,9 @@ On macOS, the terminfo for `xterm` and variants does not by default include E3,
 the terminal in question actually does support E3. For that reason, default behaviour on macOS is
 switched to use `XtermClear` if the `TERM` starts with `xterm` and the terminfo doesn’t have E3.
 
+If the terminfo database is not available, `::default()` falls back to `XTermClear` instead of
+supplying a useless `Terminfo`. When testing, it's expected to have a functional terminfo where
+practical.
 
 Emulator libraries
 ------------------

src/lib.rs

@@ -392,7 +392,8 @@ impl Default for ClearScreen {
 
 			// - screen supports CSI 3J only within the XtermClear sequence, without E3 capability.
 			// - Konsole handles CSI 3J correctly only within the XtermClear sequence.
-			if term.starts_with("screen") || term.starts_with("konsole") {
+			// - assume tmux TERMs are only used within tmux, and avoid the requirement for a functioning terminfo then
+			if term.starts_with("screen") || term.starts_with("konsole") || term.starts_with("tmux") {
 				return Self::XtermClear;
 			}
 
@@ -406,7 +407,7 @@ impl Default for ClearScreen {
 				return Self::XtermClear;
 			}
 
-			if !term.is_empty() {
+			if !term.is_empty() && Database::from_env().is_ok() {
 				return Self::Terminfo;
 			}
 		}