Introduce default prerelease requirement

lib/rubygems/core_ext/kernel_require.rb

@@ -66,7 +66,7 @@ def require(path)
 
     if spec = Gem.find_unresolved_default_spec(path)
       begin
-        Kernel.send(:gem, spec.name, "#{Gem::Requirement.default}.a")
+        Kernel.send(:gem, spec.name, Gem::Requirement.default_prerelease)
       rescue Exception
         RUBYGEMS_ACTIVATION_MONITOR.exit
         raise

lib/rubygems/installer.rb

@@ -776,7 +776,7 @@ def app_script_text(bin_file_name)
 
 require 'rubygems'
 
-version = "#{Gem::Requirement.default}.a"
+version = "#{Gem::Requirement.default_prerelease}"
 
 str = ARGV.first
 if str

lib/rubygems/requirement.rb

@@ -32,10 +32,15 @@ class Gem::Requirement
   PATTERN = /\A#{PATTERN_RAW}\z/.freeze
 
   ##
-  # The default requirement matches any version
+  # The default requirement matches any non-prerelease version
 
   DefaultRequirement = [">=", Gem::Version.new(0)].freeze
 
+  ##
+  # The default requirement matches any version
+
+  DefaultPrereleaseRequirement = [">=", Gem::Version.new("0.a")].freeze
+
   ##
   # Raised when a bad requirement is encountered
 
@@ -73,6 +78,10 @@ def self.default
     new '>= 0'
   end
 
+  def self.default_prerelease
+    new '>= 0.a'
+  end
+
   ###
   # A source set requirement, used for Gemfiles and lockfiles
 
@@ -101,6 +110,8 @@ def self.parse(obj)
 
     if $1 == ">=" && $2 == "0"
       DefaultRequirement
+    elsif $1 == ">=" && $2 == "0.a"
+      DefaultPrereleaseRequirement
     else
       [$1 || "=", Gem::Version.new($2)]
     end