Reapply "Extract ruby_api_version_name"

This reverts commit ba2f697.

Box already used ruby_api_version_name.

Author: nurse

ruby.c

@@ -305,6 +305,8 @@ ruby_show_usage_line(const char *name, const char *secondary, const char *descri
                     description, help, highlight, width, columns);
 }
 
+RUBY_EXTERN const char ruby_api_version_name[];
+
 static void
 usage(const char *name, int help, int highlight, int columns)
 {
@@ -408,6 +410,9 @@ usage(const char *name, int help, int highlight, int columns)
 #define SHOW(m) show_usage_line(&(m), help, highlight, w, columns)
 
     printf("%sUsage:%s %s [options] [--] [filepath] [arguments]\n", sb, se, name);
+    printf("\n""Details and examples at https://docs.ruby-lang.org/en/%s/ruby/options_md.html\n",
+           ruby_api_version_name);
+
     for (i = 0; i < num; ++i)
         SHOW(usage_msg[i]);
 

version.c

@@ -25,8 +25,9 @@
 
 #ifdef RUBY_REVISION
 # if RUBY_PATCHLEVEL == -1
+#  define RUBY_API_VERSION_NAME "master"
 #  ifndef RUBY_BRANCH_NAME
-#   define RUBY_BRANCH_NAME "master"
+#   define RUBY_BRANCH_NAME RUBY_API_VERSION_NAME
 #  endif
 #  define RUBY_REVISION_STR " "RUBY_BRANCH_NAME" "RUBY_REVISION
 # else
@@ -36,6 +37,9 @@
 # define RUBY_REVISION "HEAD"
 # define RUBY_REVISION_STR ""
 #endif
+#ifndef RUBY_API_VERSION_NAME
+# define RUBY_API_VERSION_NAME RUBY_API_VERSION_STR
+#endif
 #if !defined RUBY_RELEASE_DATETIME || RUBY_PATCHLEVEL != -1
 # undef RUBY_RELEASE_DATETIME
 # define RUBY_RELEASE_DATETIME RUBY_RELEASE_DATE
@@ -45,6 +49,9 @@
 #define MKSTR(type) rb_obj_freeze(rb_usascii_str_new_static(ruby_##type, sizeof(ruby_##type)-1))
 #define MKINT(name) INT2FIX(ruby_##name)
 
+#define RUBY_API_VERSION_STR \
+    STRINGIZE(RUBY_API_VERSION_MAJOR) "." \
+    STRINGIZE(RUBY_API_VERSION_MINOR)
 const int ruby_api_version[] = {
     RUBY_API_VERSION_MAJOR,
     RUBY_API_VERSION_MINOR,
@@ -77,6 +84,7 @@ const char ruby_revision[] = RUBY_FULL_REVISION;
 const char ruby_release_date[] = RUBY_RELEASE_DATE;
 const char ruby_platform[] = RUBY_PLATFORM;
 const int ruby_patchlevel = RUBY_PATCHLEVEL;
+const char ruby_api_version_name[] = RUBY_API_VERSION_NAME;
 const char ruby_description[] =
     "ruby " RUBY_VERSION RUBY_PATCHLEVEL_STR " "
     "(" RUBY_RELEASE_DATETIME RUBY_REVISION_STR ") "