Add unref-to-strv to GStrvBuilder

For those projects that cannot use `g_autoptr()`, GStrvBuilder's end
plus unref is not really convenient.

We can crib the "unref to data type" model from GBytes, and have an
additional unref function that also returns the just built GStrv.

glib/gstrvbuilder.c

@@ -37,7 +37,10 @@
  *   g_autoptr(GStrvBuilder) builder = g_strv_builder_new ();
  *   g_strv_builder_add (builder, "hello");
  *   g_strv_builder_add (builder, "world");
+ *
  *   g_auto(GStrv) array = g_strv_builder_end (builder);
+ *
+ *   g_assert_true (g_strv_equal (array, (const char *[]) { "hello", "world", NULL }));
  * ```
  *
  * Since: 2.68
@@ -81,6 +84,43 @@ g_strv_builder_unref (GStrvBuilder *builder)
   g_ptr_array_unref (&builder->array);
 }
 
+/**
+ * g_strv_builder_unref_to_strv:
+ * @builder: (transfer full): a #GStrvBuilder
+ *
+ * Decreases the reference count on the string vector builder, and returns
+ * its contents as a `NULL`-terminated string array.
+ *
+ * This function is especially useful for cases where it's not possible
+ * to use `g_autoptr()`.
+ *
+ * ```c
+ * GStrvBuilder *builder = g_strv_builder_new ();
+ * g_strv_builder_add (builder, "hello");
+ * g_strv_builder_add (builder, "world");
+ *
+ * GStrv array = g_strv_builder_unref_to_strv (builder);
+ *
+ * g_assert_true (g_strv_equal (array, (const char *[]) { "hello", "world", NULL }));
+ *
+ * g_strfreev (array);
+ * ```
+ *
+ * Returns: (transfer full) (array zero-terminated=1): the constructed string
+ *   array
+ *
+ * Since: 2.82
+ */
+GStrv
+g_strv_builder_unref_to_strv (GStrvBuilder *builder)
+{
+  GStrv res = g_strv_builder_end (builder);
+
+  g_strv_builder_unref (builder);
+
+  return res;
+}
+
 /**
  * g_strv_builder_ref:
  * @builder: (transfer none): a #GStrvBuilder

glib/gstrvbuilder.h

@@ -38,6 +38,9 @@ GStrvBuilder *g_strv_builder_new (void);
 GLIB_AVAILABLE_IN_2_68
 void g_strv_builder_unref (GStrvBuilder *builder);
 
+GLIB_AVAILABLE_IN_2_82
+GStrv g_strv_builder_unref_to_strv (GStrvBuilder *builder);
+
 GLIB_AVAILABLE_IN_2_68
 GStrvBuilder *g_strv_builder_ref (GStrvBuilder *builder);
 

glib/tests/strvbuilder.c

@@ -122,6 +122,30 @@ test_strvbuilder_ref (void)
   g_strv_builder_unref (builder);
 }
 
+static void
+test_strvbuilder_unref_to_strv (void)
+{
+  GStrvBuilder *builder = g_strv_builder_new ();
+  GStrv result;
+
+  g_strv_builder_add_many (builder, "hello", "world", NULL);
+  result = g_strv_builder_unref_to_strv (builder);
+
+  g_assert_true (g_strv_equal ((const char * const *) result,
+                               (const char *[]) {
+                                 "hello",
+                                 "world",
+                                 NULL,
+                               }));
+
+  g_strfreev (result);
+
+  builder = g_strv_builder_new ();
+  result = g_strv_builder_unref_to_strv (builder);
+  g_assert_null (result[0]);
+  g_strfreev (result);
+}
+
 int
 main (int argc,
       char *argv[])
@@ -134,6 +158,7 @@ main (int argc,
   g_test_add_func ("/strvbuilder/add_many", test_strvbuilder_add_many);
   g_test_add_func ("/strvbuilder/take", test_strvbuilder_take);
   g_test_add_func ("/strvbuilder/ref", test_strvbuilder_ref);
+  g_test_add_func ("/strvbuilder/unref_to_strv", test_strvbuilder_unref_to_strv);
 
   return g_test_run ();
 }