Don't ever allow ~ as a startingDirectory

Basically, some WSL distros ship fragments that replace the commandline with the executable for their distro (`ubuntu.exe`, etc.). We didn't exxpect that.

Unfortunately, `~` is really never a valid path for a process on windows, so those distros would now fail with

```
[error 2147942667 (0x8007010b) when launching `ubuntu1804.exe']
Could not access starting directory "~"
```

* [x] Closes #12353
* [x] Tested with a (`ubuntu1804.exe`, `~`) profile - launched successfully, where 1.13 in market fails.

src/types/ut_types/UtilsTests.cpp

@@ -479,5 +479,29 @@ void UtilsTests::TestMangleWSLPaths()
         VERIFY_ARE_EQUAL(LR"("wsl" --cd "\\wsl.localhost\Ubuntu\home\user" -d Ubuntu)", commandline);
         VERIFY_ARE_EQUAL(L"", path);
     }
+
+    /// Tests for GH #12353
+
+    const auto expectedUserProfilePath = wil::ExpandEnvironmentStringsW<std::wstring>(L"%USERPROFILE%");
+    {
+        auto [commandline, path] = MangleStartingDirectoryForWSL(LR"(wsl -d Ubuntu)", L"~");
+        VERIFY_ARE_EQUAL(LR"("wsl" --cd "~" -d Ubuntu)", commandline);
+        VERIFY_ARE_EQUAL(L"", path);
+    }
+    {
+        auto [commandline, path] = MangleStartingDirectoryForWSL(LR"(wsl ~ -d Ubuntu)", L"~");
+        VERIFY_ARE_EQUAL(LR"(wsl ~ -d Ubuntu)", commandline);
+        VERIFY_ARE_EQUAL(expectedUserProfilePath, path);
+    }
+    {
+        auto [commandline, path] = MangleStartingDirectoryForWSL(LR"(ubuntu ~ -d Ubuntu)", L"~");
+        VERIFY_ARE_EQUAL(LR"(ubuntu ~ -d Ubuntu)", commandline);
+        VERIFY_ARE_EQUAL(expectedUserProfilePath, path);
+    }
+    {
+        auto [commandline, path] = MangleStartingDirectoryForWSL(LR"(powershell.exe)", L"~");
+        VERIFY_ARE_EQUAL(LR"(powershell.exe)", commandline);
+        VERIFY_ARE_EQUAL(expectedUserProfilePath, path);
+    }
 }
 #endif

src/types/utils.cpp

@@ -600,6 +600,7 @@ bool Utils::IsElevated()
 std::tuple<std::wstring, std::wstring> Utils::MangleStartingDirectoryForWSL(std::wstring_view commandLine,
                                                                             std::wstring_view startingDirectory)
 {
+    bool executableWasWSL{ false };
     do
     {
         if (startingDirectory.size() > 0 && commandLine.size() >= 3)
@@ -611,6 +612,7 @@ std::tuple<std::wstring, std::wstring> Utils::MangleStartingDirectoryForWSL(std:
             const auto executableFilename{ executablePath.filename().wstring() };
             if (executableFilename == L"wsl" || executableFilename == L"wsl.exe")
             {
+                executableWasWSL = true;
                 // We've got a WSL -- let's just make sure it's the right one.
                 if (executablePath.has_parent_path())
                 {
@@ -670,8 +672,15 @@ std::tuple<std::wstring, std::wstring> Utils::MangleStartingDirectoryForWSL(std:
         }
     } while (false);
 
+    // GH #12353: `~` is never a valid windows path. We can only accept that as
+    // a startingDirectory when the exe is specifically wsl.exe, because that
+    // can override the real startingDirectory. If the user set the
+    // startingDirectory to ~, but the commandline to something like pwsh.exe,
+    // that won't actually work. In that case, mangle the startingDirectory to
+    // %userprofile%, so it's at least something reasonable.
     return {
         std::wstring{ commandLine },
-        std::wstring{ startingDirectory }
+        std::wstring{ startingDirectory == L"~" ? wil::ExpandEnvironmentStringsW<std::wstring>(L"%USERPROFILE%") :
+                                                  startingDirectory }
     };
 }