handle errors in editing files

src/env.rs

@@ -0,0 +1,11 @@
+use std::env::var;
+
+use anyhow::{anyhow, Result};
+
+pub(crate) fn get_editor() -> Result<String> {
+    check_vars_in_order(&["EDITOR", "VISUAL"]).ok_or_else(|| anyhow!("could not find editor"))
+}
+
+fn check_vars_in_order(vars: &[&str]) -> Option<String> {
+    vars.iter().flat_map(|v| var(v).ok()).next()
+}