Implement rich RPM dependencies

This implements rich RPM dependencies, which are available with RPM
4.14+ (introduced in Fedora 27[1]). This means only a single line for a
dependency is used. That doesn't play well with the
.with_requires.commented_out approach that was implemented. This instead
uses parameters.

An alternative approach could be to move this to the template.

[1]: https://fedoraproject.org/wiki/Changes/RPM-4.14

lib/gem2rpm/rpm_dependency.rb

@@ -47,5 +47,23 @@ def to_rpm
       end
       rpm_dependencies.join("\n")
     end
+
+    # Returns string with entry suitable for RPM .spec file with RPM 4.14+.
+    def to_rich_rpm(with_requires: false, commented_out: false)
+      rpm_dependencies = requirement.map do |version|
+        version.to_s.empty? ? name : "#{name} #{version}"
+      end
+      result = rpm_dependencies.size == 1 ? reqs.first : "(#{reqs.join(' with ')})"
+
+      if with_requires
+        result.prepend(dep.type == :development ? 'BuildRequires: ' : 'Requires: ')
+      end
+
+      if commented_out
+        result.prepend('# ')
+      end
+
+      result
+    end
   end
 end

lib/gem2rpm/rpm_dependency_list.rb

@@ -50,11 +50,21 @@ def comment_out
     end
 
     # Returns string with all dependencies from the list converted into entries
-    # suitable for RPM .spec file. Thise entries should include all necessary
+    # suitable for RPM .spec file. These entries should include all necessary
     # macros depending on file categorization.
     def to_rpm
       s = entries.map(&:to_rpm).join("\n")
       s += "\n" unless s.empty?
     end
+
+    # Returns a string with all dependencies from the list converted into entries
+    # suitable for RPM .spec file with RPM 4.14+. Thise entries should include
+    # all necessary macros depending on file categorization.
+    def to_rich_rpm(with_requires: false, commented_out: false)
+      s = entries.map do |entry|
+        entry.to_rich_rpm(with_requires: with_requires, comment_out: comment_out)
+      end.join("\n")
+      s += "\n" unless s.empty?
+    end
   end
 end

templates/fedora-27-rawhide.spec.erb

@@ -24,7 +24,7 @@ BuildRequires: gcc
 <% end -%>
 <%= development_dependencies.reject do |d|
   ["rdoc", "rake", "bundler"].include? d.name
-end.virtualize.with_requires.comment_out.to_rpm -%>
+end.virtualize.to_rich_rpm(with_requires: true, comment_out: true) -%>
 <% if spec.extensions.empty? -%>
 BuildArch: noarch
 <% end -%>