os: deprioritize GHOSTTY_RESOURCES_DIR for debug builds

When one develops Ghostty while using Ghostty it could lead to an
interesting conundrum: the freshly built Ghostty would use the parent
Ghostty's resources, which would be stale and not reflect any new
changes to resources. This is especially bad for translators, since
their translations would not be reflected in the newly built Ghostty
if they happen to run it under older Ghostty, which is not only
counterintuitive and also painful in terms of workflow.

Now, on debug builds we always try to use the terminfo detection method
first in order to locate the zig-out/share/ghostty folder, and only fall
back to GHOSTTY_RESOURCES_DIR if the executable is for some reason no
longer in zig-out. You can test this behavior by manually moving the
Ghostty executable out of zig-out, and then launching it with and without
Ghostty.

src/os/resourcesdir.zig

@@ -9,14 +9,22 @@ const Allocator = std.mem.Allocator;
 /// This is highly Ghostty-specific and can likely be generalized at
 /// some point but we can cross that bridge if we ever need to.
 pub fn resourcesDir(alloc: std.mem.Allocator) !?[]const u8 {
-    // If we have an environment variable set, we always use that.
+    // Use the GHOSTTY_RESOURCES_DIR environment variable in release builds.
+    //
+    // In debug builds we try using terminfo detection first instead, since
+    // if debug Ghostty is launched by an older version of Ghostty, it
+    // would inherit the old, stale resources of older Ghostty instead of the
+    // freshly built ones under zig-out/share/ghostty.
+    //
     // Note: we ALWAYS want to allocate here because the result is always
     // freed, do not try to use internal_os.getenv or posix getenv.
-    if (std.process.getEnvVarOwned(alloc, "GHOSTTY_RESOURCES_DIR")) |dir| {
-        if (dir.len > 0) return dir;
-    } else |err| switch (err) {
-        error.EnvironmentVariableNotFound => {},
-        else => return err,
+    if (comptime builtin.mode != .Debug) {
+        if (std.process.getEnvVarOwned(alloc, "GHOSTTY_RESOURCES_DIR")) |dir| {
+            if (dir.len > 0) return dir;
+        } else |err| switch (err) {
+            error.EnvironmentVariableNotFound => {},
+            else => return err,
+        }
     }
 
     // This is the sentinel value we look for in the path to know
@@ -52,6 +60,17 @@ pub fn resourcesDir(alloc: std.mem.Allocator) !?[]const u8 {
         }
     }
 
+    // If terminfo detection failed in debug builds (somehow),
+    // fallback and use the provided resources dir.
+    if (comptime builtin.mode == .Debug) {
+        if (std.process.getEnvVarOwned(alloc, "GHOSTTY_RESOURCES_DIR")) |dir| {
+            if (dir.len > 0) return dir;
+        } else |err| switch (err) {
+            error.EnvironmentVariableNotFound => {},
+            else => return err,
+        }
+    }
+
     return null;
 }