termio/exec: only add ghostty path if it isn't already in path

src/os/env.zig

@@ -2,6 +2,12 @@ const std = @import("std");
 const builtin = @import("builtin");
 const Allocator = std.mem.Allocator;
 
+/// The separator used in environment variables such as PATH.
+pub const PATH_SEP = switch (builtin.os.tag) {
+    .windows => ";",
+    else => ":",
+};
+
 /// Append a value to an environment variable such as PATH.
 /// The returned value is always allocated so it must be freed.
 pub fn appendEnv(
@@ -13,14 +19,9 @@ pub fn appendEnv(
     if (current.len == 0) return try alloc.dupe(u8, value);
 
     // Otherwise we must prefix.
-    const sep = switch (builtin.os.tag) {
-        .windows => ";",
-        else => ":",
-    };
-
     return try std.fmt.allocPrint(alloc, "{s}{s}{s}", .{
         current,
-        sep,
+        PATH_SEP,
         value,
     });
 }

src/termio/Exec.zig

@@ -962,10 +962,20 @@ const Subprocess = struct {
             // Append if we have a path. We want to append so that ghostty is
             // the last priority in the path. If we don't have a path set
             // then we just set it to the directory of the binary.
-            try env.put("PATH", if (env.get("PATH")) |path|
-                try internal_os.appendEnv(alloc, path, exe_dir)
-            else
-                exe_dir);
+            if (env.get("PATH")) |path| {
+                // Verify that our path doesn't already contain this entry
+                var it = std.mem.tokenizeScalar(u8, path, internal_os.PATH_SEP[0]);
+                while (it.next()) |entry| {
+                    if (std.mem.eql(u8, entry, exe_dir)) break :ghostty_path;
+                }
+
+                try env.put(
+                    "PATH",
+                    try internal_os.appendEnv(alloc, path, exe_dir),
+                );
+            } else {
+                try env.put("PATH", exe_dir);
+            }
         }
 
         // Set environment variables used by some programs (such as neovim) to detect