Simplify nvim version check, remove regex dependency

Using `has("nvim-0.4")` check seems more robust than using a regex to
parse the version string. This also means regex is no longer a runtime
dependency.

Cargo.toml

@@ -42,7 +42,6 @@ futures = "0.3.12"
 glutin = { git = "https://github.com/Kethku/glutin", branch = "new-keyboard-all" }
 winit = { git = "https://github.com/Kethku/winit", branch = "new-keyboard-all", default-features = false }
 gl = "0.14.0"
-regex = "1.5.4"
 swash = "0.1.4"
 clap="2.33.3"
 

src/bridge/mod.rs

@@ -21,7 +21,6 @@ use crate::settings::*;
 use crate::{cmd_line::CmdLineSettings, error_handling::ResultPanicExplanation};
 pub use events::*;
 use handler::NeovimHandler;
-use regex::Regex;
 pub use tx_wrapper::{TxWrapper, WrapTx};
 pub use ui_commands::UiCommand;
 
@@ -188,16 +187,13 @@ async fn start_neovim_runtime(
         close_watcher_running.store(false, Ordering::Relaxed);
     });
 
-    if let Ok(output) = nvim.command_output("version").await {
-        let re = Regex::new(r"NVIM v0.[4-9]\d*.\d+").unwrap();
-        if !re.is_match(&output) {
+    match nvim.command_output("echo has('nvim-0.4')").await.as_deref() {
+        Ok("1") => {} // This is just a guard
+        _ => {
             error!("Neovide requires nvim version 0.4 or higher. Download the latest version here https://github.com/neovim/neovim/wiki/Installing-Neovim");
             std::process::exit(0);
         }
-    } else {
-        error!("Neovide requires nvim version 0.4 or higher. Download the latest version here https://github.com/neovim/neovim/wiki/Installing-Neovim");
-        std::process::exit(0);
-    };
+    }
 
     nvim.set_var("neovide", Value::Boolean(true))
         .await