Replace deprecated commands (#27)

See https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

src/GitHubActions.jl

@@ -116,7 +116,7 @@ log_warning(msg) = command("warning", (), msg)
 
 Save value `v` with name `k` to state.
 """
-save_state(k, v) = command("save-state", (name=k,), v)
+save_state(k, v) = add_to_file("GITHUB_STATE", "$k=$v")
 
 """
     set_command_echo(enable)
@@ -130,7 +130,7 @@ set_command_echo(enable) = command("echo", (), enable ? "on" : "off")
 
 Set the output with name `k` to value `v`.
 """
-set_output(k, v) = command("set-output", (name=k,), v)
+set_output(k, v) = add_to_file("GITHUB_OUTPUT", "$k=$v")
 
 """
     set_secret(v)

test/runtests.jl

@@ -27,12 +27,22 @@ const GHA = GitHubActions
     @test (@capture_out log_error("a")) == "::error::a\n"
     @test (@capture_out log_warning("a")) == "::warning::a\n"
 
-    @test (@capture_out save_state("a", "b")) == "::save-state name=a::b\n"
+    mktemp() do file, io
+        withenv("GITHUB_STATE" => file) do
+            save_state("a", "b")
+            @test read(file, String) == "a=b\n"
+        end
+    end
 
     @test (@capture_out set_command_echo(true)) == "::echo::on\n"
     @test (@capture_out set_command_echo(false)) == "::echo::off\n"
 
-    @test (@capture_out set_output("a", "b")) == "::set-output name=a::b\n"
+    mktemp() do file, io
+        withenv("GITHUB_OUTPUT" => file) do
+            set_output("a", "b")
+            @test read(file, String) == "a=b\n"
+        end
+    end
 
     @test (@capture_out set_secret("a")) == "::add-mask::a\n"