Use same logic for skipping single instance check on Linux as on Mac/Win (#19446)

Release Notes:

- Linux: Now skips check which exits with "zed is already running" when
in development mode or when run with `zed-local`, matching the behavior
on Mac and Windows

Co-authored-by: Nathan Sobo <nathan@zed.dev>

crates/zed/src/main.rs

@@ -32,7 +32,7 @@ use node_runtime::{NodeBinaryOptions, NodeRuntime};
 use parking_lot::Mutex;
 use project::project_settings::ProjectSettings;
 use recent_projects::{open_ssh_project, SshSettings};
-use release_channel::{AppCommitSha, AppVersion};
+use release_channel::{AppCommitSha, AppVersion, ReleaseChannel};
 use session::{AppSession, Session};
 use settings::{
     handle_settings_file_changes, watch_config_file, InvalidSettingsError, Settings, SettingsStore,
@@ -164,33 +164,30 @@ fn main() {
 
     let (open_listener, mut open_rx) = OpenListener::new();
 
+    let failed_single_instance_check =
+        if *db::ZED_STATELESS || *release_channel::RELEASE_CHANNEL == ReleaseChannel::Dev {
+            false
+        } else {
             #[cfg(target_os = "linux")]
             {
-        if env::var("ZED_STATELESS").is_err() {
+                crate::zed::listen_for_cli_connections(open_listener.clone()).is_err()
-            if crate::zed::listen_for_cli_connections(open_listener.clone()).is_err() {
-                println!("zed is already running");
-                return;
-            }
-        }
             }
 
             #[cfg(target_os = "windows")]
             {
-        use zed::windows_only_instance::*;
+                !crate::zed::windows_only_instance::check_single_instance()
-        if !check_single_instance() {
-            println!("zed is already running");
-            return;
-        }
             }
 
             #[cfg(target_os = "macos")]
             {
                 use zed::mac_only_instance::*;
-        if ensure_only_instance() != IsOnlyInstance::Yes {
+                ensure_only_instance() != IsOnlyInstance::Yes
+            }
+        };
+    if failed_single_instance_check {
         println!("zed is already running");
         return;
     }
-    }
 
     let git_hosting_provider_registry = Arc::new(GitHostingProviderRegistry::new());
     let git_binary_path =

crates/zed/src/zed/mac_only_instance.rs

@@ -87,10 +87,6 @@ pub enum IsOnlyInstance {
 }
 
 pub fn ensure_only_instance() -> IsOnlyInstance {
-    if *db::ZED_STATELESS || *release_channel::RELEASE_CHANNEL == ReleaseChannel::Dev {
-        return IsOnlyInstance::Yes;
-    }
-
     if check_got_handshake() {
         return IsOnlyInstance::No;
     }

crates/zed/src/zed/windows_only_instance.rs

@@ -17,14 +17,6 @@ fn retrieve_app_instance_event_identifier() -> &'static str {
 }
 
 pub fn check_single_instance() -> bool {
-    if *db::ZED_STATELESS || *release_channel::RELEASE_CHANNEL == ReleaseChannel::Dev {
-        return true;
-    }
-
-    check_single_instance_event()
-}
-
-fn check_single_instance_event() -> bool {
     unsafe {
         CreateEventW(
             None,