Add basic ~ support

src/main.zig

@@ -163,6 +163,7 @@ fn cdFn(shell_state: *ShellState, command: [][]const u8, allocator: Allocator) !
     const old_pwd = env_map.get("OLDPWD");
     const home = env_map.get("HOME");
     defer allocator.free(pwd);
+    var buf: [fs.max_path_bytes]u8 = undefined;
     var err: ?anyerror = null;
 
     var target: ?[]const u8 = null;
@@ -170,6 +171,12 @@ fn cdFn(shell_state: *ShellState, command: [][]const u8, allocator: Allocator) !
         if (home) |h| {
             target = h;
         }
+    } else if (command[1][0] == '~') {
+        if (home) |h| {
+            const numReplacements = mem.replace(u8, command[1], "~", h, &buf);
+            const len = command[1].len - numReplacements + (numReplacements * h.len);
+            target = buf[0..len];
+        }
     } else if (eql(u8, command[1], "-")) {
         if (old_pwd) |old| {
             target = old;
@@ -178,7 +185,6 @@ fn cdFn(shell_state: *ShellState, command: [][]const u8, allocator: Allocator) !
             return;
         }
     } else {
-        var buf: [fs.max_path_bytes]u8 = undefined;
         target = cwd.realpath(command[1], &buf) catch |e| blk: {
             err = e;
             break :blk null;