Handle `$BIZHAWK_DATA_HOME` nicely instead of w/ a hack in `Database`

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -343,7 +343,10 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			//do this threaded stuff early so it has plenty of time to run in background
-			Database.InitializeDatabase(Path.Combine(PathUtils.ExeDirectoryPath, "gamedb", "gamedb.txt"), silent: true);
+			Database.InitializeDatabase(
+				bundledRoot: Path.Combine(PathUtils.ExeDirectoryPath, "gamedb"),
+				userRoot: Path.Combine(PathUtils.DataDirectoryPath, "gamedb"),
+				silent: true);
 			BootGodDb.Initialize(Path.Combine(PathUtils.ExeDirectoryPath, "gamedb"));
 
 			_argParser = cliFlags;

src/BizHawk.Common/Extensions/PathExtensions.cs

@@ -165,6 +165,13 @@ namespace BizHawk.Common.PathExtensions
 
 	public static class PathUtils
 	{
+		/// <returns>absolute path of the user data dir <c>$BIZHAWK_DATA_HOME</c>, or fallback value equal to <see cref="ExeDirectoryPath"/></returns>
+		/// <remarks>
+		/// returned string omits trailing slash<br/>
+		/// on Windows, the env. var is ignored and the fallback of <see cref="ExeDirectoryPath"/> is always used
+		/// </remarks>
+		public static readonly string DataDirectoryPath;
+
 		/// <returns>absolute path of the dll dir (sibling of EmuHawk.exe)</returns>
 		/// <remarks>returned string omits trailing slash</remarks>
 		public static readonly string DllDirectoryPath;
@@ -181,6 +188,20 @@ namespace BizHawk.Common.PathExtensions
 				: string.IsNullOrEmpty(dirPath) ? throw new Exception("failed to get location of executable, very bad things must have happened") : dirPath.RemoveSuffix('\\');
 			DllDirectoryPath = Path.Combine(OSTailoredCode.IsUnixHost && ExeDirectoryPath == string.Empty ? "/" : ExeDirectoryPath, "dll");
 			// yes, this is a lot of extra code to make sure BizHawk can run in `/` on Unix, but I've made up for it by caching these for the program lifecycle --yoshi
+			DataDirectoryPath = ExeDirectoryPath;
+			if (OSTailoredCode.IsUnixHost)
+			{
+				var envVar = Environment.GetEnvironmentVariable("BIZHAWK_DATA_HOME");
+				try
+				{
+					envVar = envVar?.MakeAbsolute() ?? string.Empty;
+					if (Directory.Exists(envVar)) DataDirectoryPath = envVar;
+				}
+				catch
+				{
+					// ignored
+				}
+			}
 		}
 	}
 }

src/BizHawk.Emulation.Common/Database/Database.cs

@@ -181,22 +181,19 @@ namespace BizHawk.Emulation.Common
 			acquire.Set();
 		}
 
-		public static void InitializeDatabase(string path, bool silent)
+		public static void InitializeDatabase(string bundledRoot, string userRoot, bool silent)
 		{
 			if (initialized) throw new InvalidOperationException("Did not expect re-initialize of game Database");
 			initialized = true;
 
-			_bundledRoot = Path.GetDirectoryName(path);
-			_userRoot = Environment.GetEnvironmentVariable("BIZHAWK_DATA_HOME");
-			if (!string.IsNullOrEmpty(_userRoot) && Directory.Exists(_userRoot)) _userRoot = Path.Combine(_userRoot, "gamedb");
-			else _userRoot = _bundledRoot;
-			Console.WriteLine($"user root: {_userRoot}");
+			_bundledRoot = bundledRoot;
+			_userRoot = Directory.Exists(userRoot) ? userRoot : bundledRoot;
 
 			_expected = new DirectoryInfo(_bundledRoot!).EnumerateFiles("*.txt").Select(static fi => fi.Name).ToList();
 
 			var stopwatch = Stopwatch.StartNew();
 			ThreadPool.QueueUserWorkItem(_=> {
-				initializeWork(path, inUser: false, silent: silent);
+				initializeWork(Path.Combine(bundledRoot, "gamedb.txt"), inUser: false, silent: silent);
 				if (_expected.Count is not 0) Util.DebugWriteLine($"extra bundled gamedb files were not #included: {string.Join(", ", _expected)}");
 				Util.DebugWriteLine("GameDB load: " + stopwatch.Elapsed + " sec");
 			});