feat(external-tools): force tools to open in new windows where needed

Adds a helper that forces selected tools to launch in a new window
instead of reusing the current one. This is applied to code editors,
diff/merge, and terminal launches, aligning behavior across platforms.
Presets and defaults are updated to pass new-window or equivalent flags,
and tests verify the new behavior for common tools.

- Update code editors to always use a new window when opened
- Normalize launch flags for Windows terminals and diff tools
- Add tests covering new-window behavior for common tools

src-tauri/src/external_tools.rs

@@ -405,8 +405,10 @@ fn known_tools() -> Vec<ToolSpec> {
         tool(
             "git-bash",
             "Git Bash",
-            &["bash.exe"],
+            &["git-bash.exe", "bash.exe"],
             &[
+                r"%PROGRAMFILES%\Git\git-bash.exe",
+                r"%LOCALAPPDATA%\Programs\Git\git-bash.exe",
                 r"%PROGRAMFILES%\Git\bin\bash.exe",
                 r"%LOCALAPPDATA%\Programs\Git\bin\bash.exe",
             ],
@@ -1350,6 +1352,101 @@ fn expand_args(
         .collect()
 }
 
+fn command_in_new_window(mut command: ExternalToolCommand) -> ExternalToolCommand {
+    let executable = Path::new(command.program.trim())
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or(command.program.trim())
+        .to_ascii_lowercase();
+
+    let remove_flags = |args: &mut Vec<String>, flags: &[&str]| {
+        args.retain(|arg| !flags.iter().any(|flag| arg.eq_ignore_ascii_case(flag)));
+    };
+    let prepend_flag = |args: &mut Vec<String>, flag: &str| {
+        if !args.iter().any(|arg| arg.eq_ignore_ascii_case(flag)) {
+            args.insert(0, flag.to_string());
+        }
+    };
+
+    if matches!(
+        executable.as_str(),
+        "code"
+            | "code.exe"
+            | "code-insiders"
+            | "code-insiders.exe"
+            | "code - insiders.exe"
+            | "cursor"
+            | "cursor.exe"
+            | "windsurf"
+            | "windsurf.exe"
+            | "vscodium"
+            | "vscodium.exe"
+            | "codium"
+            | "codium.exe"
+    ) {
+        remove_flags(&mut command.args, &["--reuse-window", "-r"]);
+        prepend_flag(&mut command.args, "--new-window");
+    } else if matches!(executable.as_str(), "zed" | "zed.exe") {
+        remove_flags(&mut command.args, &["--reuse", "-r"]);
+        prepend_flag(&mut command.args, "--new");
+    } else if matches!(
+        executable.as_str(),
+        "subl" | "subl.exe" | "sublime_text" | "sublime_text.exe"
+    ) {
+        prepend_flag(&mut command.args, "--new-window");
+    } else if executable == "notepad++.exe" {
+        prepend_flag(&mut command.args, "-multiInst");
+    } else if executable == "kate" || executable == "kate.exe" {
+        prepend_flag(&mut command.args, "--new");
+    } else if executable == "geany" || executable == "geany.exe" {
+        prepend_flag(&mut command.args, "--new-instance");
+    } else if executable == "wt" || executable == "wt.exe" {
+        let mut index = 0;
+        while index < command.args.len() {
+            let is_window = command.args[index].eq_ignore_ascii_case("-w")
+                || command.args[index].eq_ignore_ascii_case("--window")
+                || command.args[index]
+                    .to_ascii_lowercase()
+                    .starts_with("--window=");
+            if is_window {
+                let has_separate_value = !command.args[index].contains('=');
+                command.args.remove(index);
+                if has_separate_value && index < command.args.len() {
+                    command.args.remove(index);
+                }
+            } else {
+                index += 1;
+            }
+        }
+        command
+            .args
+            .splice(0..0, ["-w".to_string(), "new".to_string()]);
+    } else if executable == "explorer" || executable == "explorer.exe" {
+        prepend_flag(&mut command.args, "/n,");
+    } else if matches!(
+        executable.as_str(),
+        "totalcmd" | "totalcmd.exe" | "totalcmd64" | "totalcmd64.exe"
+    ) {
+        command
+            .args
+            .retain(|arg| !arg.to_ascii_lowercase().starts_with("/o"));
+        prepend_flag(&mut command.args, "/N");
+    } else if executable == "open" {
+        prepend_flag(&mut command.args, "-n");
+    } else if executable.starts_with("bcomp") {
+        remove_flags(&mut command.args, &["/solo", "-solo"]);
+        #[cfg(windows)]
+        prepend_flag(&mut command.args, "/solo");
+        #[cfg(not(windows))]
+        prepend_flag(&mut command.args, "-solo");
+    } else if executable == "winmergeu" || executable == "winmergeu.exe" {
+        remove_flags(&mut command.args, &["/s", "/sw", "-s", "-sw"]);
+        prepend_flag(&mut command.args, "/s-");
+    }
+
+    command
+}
+
 fn tool_values(repo: &Path, file: Option<&Path>) -> BTreeMap<&'static str, String> {
     let mut values = BTreeMap::new();
     values.insert("repo", repo.to_string_lossy().into_owned());
@@ -1371,11 +1468,10 @@ fn spawn_tool(
     repo: &Path,
     values: BTreeMap<&str, String>,
 ) -> Result<(), String> {
+    let command = command_in_new_window(command);
     let args = expand_args(&command, &values)?;
     let mut process = Command::new(command.program.trim());
     process.args(args).current_dir(repo);
-    #[cfg(windows)]
-    process.creation_flags(CREATE_NO_WINDOW);
     process
         .spawn()
         .map_err(|error| format!("Could not launch external tool: {error}"))?;
@@ -1388,6 +1484,7 @@ fn run_tool(
     values: BTreeMap<&str, String>,
     kind: ExternalToolRunKind,
 ) -> Result<(), String> {
+    let command = command_in_new_window(command);
     let args = expand_args(&command, &values)?;
     let program = command.program.trim().to_owned();
     let mut process = Command::new(command.program.trim());
@@ -1580,6 +1677,62 @@ mod tests {
         );
     }
 
+    #[test]
+    fn forces_code_family_tools_into_a_new_window() {
+        let command = command_in_new_window(ExternalToolCommand {
+            program: "C:/Program Files/Microsoft VS Code/Code.exe".into(),
+            args: vec![
+                "--reuse-window".into(),
+                "--diff".into(),
+                "{left}".into(),
+                "{right}".into(),
+            ],
+        });
+
+        assert_eq!(
+            command.args,
+            vec!["--new-window", "--diff", "{left}", "{right}"]
+        );
+    }
+
+    #[test]
+    fn forces_windows_terminal_to_use_a_fresh_window() {
+        let command = command_in_new_window(ExternalToolCommand {
+            program: "wt.exe".into(),
+            args: vec![
+                "--window".into(),
+                "last".into(),
+                "-d".into(),
+                "{repo}".into(),
+            ],
+        });
+
+        assert_eq!(command.args, vec!["-w", "new", "-d", "{repo}"]);
+    }
+
+    #[test]
+    fn forces_single_instance_compare_and_file_tools_into_new_windows() {
+        let beyond = command_in_new_window(ExternalToolCommand {
+            program: "BCompare.exe".into(),
+            args: vec!["/readonly".into(), "{left}".into(), "{right}".into()],
+        });
+        let winmerge = command_in_new_window(ExternalToolCommand {
+            program: "WinMergeU.exe".into(),
+            args: vec!["/s".into(), "{left}".into(), "{right}".into()],
+        });
+        let total_commander = command_in_new_window(ExternalToolCommand {
+            program: "TOTALCMD64.EXE".into(),
+            args: vec!["/O".into(), "/T".into(), "{repo}".into()],
+        });
+
+        #[cfg(windows)]
+        assert_eq!(beyond.args[0], "/solo");
+        #[cfg(not(windows))]
+        assert_eq!(beyond.args[0], "-solo");
+        assert_eq!(winmerge.args, vec!["/s-", "{left}", "{right}"]);
+        assert_eq!(total_commander.args, vec!["/N", "/T", "{repo}"]);
+    }
+
     #[test]
     fn rejects_unknown_placeholder() {
         let command = ExternalToolCommand {