Add Process::Status#exit_signal?

spec/std/process/status_spec.cr

@@ -99,6 +99,13 @@ describe Process::Status do
     err1.hash.should eq(err2.hash)
   end
 
+  it "#exit_signal?" do
+    Process::Status.new(exit_status(0)).exit_signal?.should be_nil
+    Process::Status.new(exit_status(1)).exit_signal?.should be_nil
+
+    status_for(:interrupted).exit_signal?.should eq({% if flag?(:unix) %}Signal::INT{% else %}nil{% end %})
+  end
+
   {% if flag?(:unix) && !flag?(:wasi) %}
     it "#exit_signal" do
       Process::Status.new(Signal::HUP.value).exit_signal.should eq Signal::HUP
@@ -110,6 +117,16 @@ describe Process::Status do
       Process::Status.new(unknown_signal.value).exit_signal.should eq unknown_signal
     end
 
+    it "#exit_signal?" do
+      Process::Status.new(Signal::HUP.value).exit_signal?.should eq Signal::HUP
+      Process::Status.new(Signal::INT.value).exit_signal?.should eq Signal::INT
+      last_signal = Signal.values[-1]
+      Process::Status.new(last_signal.value).exit_signal?.should eq last_signal
+
+      unknown_signal = Signal.new(126)
+      Process::Status.new(unknown_signal.value).exit_signal?.should eq unknown_signal
+    end
+
     it "#normal_exit? with signal code" do
       Process::Status.new(0x00).normal_exit?.should be_true
       Process::Status.new(0x01).normal_exit?.should be_false

src/process/status.cr

@@ -223,6 +223,20 @@ class Process::Status
     {% end %}
   end
 
+  # Returns the exit `Signal` or `nil` if there is none.
+  #
+  # On Windows returns always `nil`.
+  #
+  # * `#exit_reason` is a portable alternative.
+  def exit_signal? : Signal?
+    {% if flag?(:unix) && !flag?(:wasm32) %}
+      code = signal_code
+      unless code.zero?
+        Signal.new(code)
+      end
+    {% end %}
+  end
+
   # Returns the exit code of the process if it exited normally (`#normal_exit?`).
   #
   # Raises `RuntimeError` if the status describes an abnormal exit.