fix(terminal): keep Windows shell paths intact (#1723)

The terminal's Shell path setting was split with POSIX rules, where a backslash escapes the next character, so C:\Windows\system32\cmd.exe reached the backend as C:Windowssystem32cmd.exe and every new terminal failed to start. On Windows a backslash is now a path separator, and an unquoted path up to its .exe/.cmd/.bat/.com is the program even with spaces; paths picked from the Installed Shells menu or Browse are quoted when they contain whitespace. This was the only place the setting is parsed.

Fixes #1327

src/platform/commandLine.test.ts

@@ -0,0 +1,54 @@
+import { describe, expect, it } from "vitest";
+import { parseShellCommand, quotePath } from "./commandLine";
+
+describe("parseShellCommand", () => {
+  it("keeps Windows paths as typed", () => {
+    expect(parseShellCommand(String.raw`C:\Windows\system32\cmd.exe`, true)).toEqual([
+      String.raw`C:\Windows\system32\cmd.exe`,
+    ]);
+    expect(parseShellCommand(String.raw`C:\Windows\system32\cmd.exe /k C:\tools\init.bat`, true)).toEqual([
+      String.raw`C:\Windows\system32\cmd.exe`,
+      "/k",
+      String.raw`C:\tools\init.bat`,
+    ]);
+  });
+
+  it("takes an unquoted Windows path with spaces up to its executable", () => {
+    expect(parseShellCommand(String.raw`C:\Program Files\PowerShell\7\pwsh.exe`, true)).toEqual([
+      String.raw`C:\Program Files\PowerShell\7\pwsh.exe`,
+    ]);
+    expect(parseShellCommand(String.raw`C:\Program Files\Git\bin\bash.EXE --login -i`, true)).toEqual([
+      String.raw`C:\Program Files\Git\bin\bash.EXE`,
+      "--login",
+      "-i",
+    ]);
+  });
+
+  it("honours quotes", () => {
+    expect(parseShellCommand(String.raw`"C:\Program Files\Git\bin\bash.exe" --login`, true)).toEqual([
+      String.raw`C:\Program Files\Git\bin\bash.exe`,
+      "--login",
+    ]);
+    expect(parseShellCommand(`/bin/zsh --login`, false)).toEqual(["/bin/zsh", "--login"]);
+    expect(parseShellCommand(`"/Applications/My Shell/bin/fish" -l`, false)).toEqual([
+      "/Applications/My Shell/bin/fish",
+      "-l",
+    ]);
+    expect(parseShellCommand(String.raw`/bin/sh -c a\ b`, false)).toEqual(["/bin/sh", "-c", "a b"]);
+  });
+
+  it("is empty for an empty setting", () => {
+    expect(parseShellCommand("  ", true)).toEqual([]);
+    expect(parseShellCommand("", false)).toEqual([]);
+  });
+});
+
+describe("quotePath", () => {
+  it("quotes only paths with whitespace", () => {
+    expect(quotePath(String.raw`C:\Windows\system32\cmd.exe`)).toBe(String.raw`C:\Windows\system32\cmd.exe`);
+    expect(quotePath(String.raw`C:\Program Files\PowerShell\7\pwsh.exe`)).toBe(
+      String.raw`"C:\Program Files\PowerShell\7\pwsh.exe"`,
+    );
+    expect(parseShellCommand(quotePath("/Applications/My Shell/fish"), false)).toEqual(["/Applications/My Shell/fish"]);
+  });
+});