[clang-tidy] mark single argument constructors explicit

Found with hicpp-explicit-conversions

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/builtin_argparse.cpp

@@ -40,7 +40,7 @@ struct option_spec_t {
     int num_allowed{0};
     int num_seen{0};
 
-    option_spec_t(wchar_t s) : short_flag(s) {}
+    explicit option_spec_t(wchar_t s) : short_flag(s) {}
 };
 using option_spec_ref_t = std::unique_ptr<option_spec_t>;
 

src/env_universal_common.cpp

@@ -1299,7 +1299,7 @@ class universal_notifier_named_pipe_t : public universal_notifier_t {
     }
 
    public:
-    universal_notifier_named_pipe_t(const wchar_t *test_path)
+    explicit universal_notifier_named_pipe_t(const wchar_t *test_path)
         : pipe_fd(-1),
           readback_time_usec(0),
           readback_amount(0),

src/iothread.cpp

@@ -58,7 +58,7 @@ struct main_thread_request_t {
     relaxed_atomic_bool_t done{false};
     void_function_t func;
 
-    main_thread_request_t(void_function_t &&f) : func(f) {}
+    explicit main_thread_request_t(void_function_t &&f) : func(f) {}
 
     // No moving OR copying
     // main_thread_requests are always stack allocated, and we deal in pointers to them

src/screen.cpp

@@ -59,7 +59,7 @@ class scoped_buffer_t {
     screen_t &screen_;
 
    public:
-    scoped_buffer_t(screen_t &s) : screen_(s) { screen_.outp().beginBuffering(); }
+    explicit scoped_buffer_t(screen_t &s) : screen_(s) { screen_.outp().beginBuffering(); }
 
     ~scoped_buffer_t() { screen_.outp().endBuffering(); }
 };