Add String#delete_prefix backport.

Library/Homebrew/dev-cmd/bottle.rb

@@ -382,7 +382,7 @@ module Homebrew
       f.full_name => {
         "formula" => {
           "pkg_version" => f.pkg_version.to_s,
-          "path" => f.path.to_s.strip_prefix("#{HOMEBREW_REPOSITORY}/"),
+          "path" => f.path.to_s.delete_prefix("#{HOMEBREW_REPOSITORY}/"),
         },
         "bottle" => {
           "root_url" => bottle.root_url,

Library/Homebrew/dev-cmd/pull.rb

@@ -127,7 +127,7 @@ module Homebrew
       if (testing_match = arg.match %r{/job/Homebrew.*Testing/(\d+)/})
         tap = ARGV.value("tap")
         tap = if tap&.start_with?("homebrew/")
-          Tap.fetch("homebrew", tap.strip_prefix("homebrew/"))
+          Tap.fetch("homebrew", tap.delete_prefix("homebrew/"))
         elsif tap
           odie "Tap option did not start with \"homebrew/\": #{tap}"
         else

Library/Homebrew/extend/ARGV.rb

@@ -118,7 +118,7 @@ module HomebrewArgvExtension
   def value(name)
     arg_prefix = "--#{name}="
     flag_with_value = find { |arg| arg.start_with?(arg_prefix) }
-    flag_with_value&.strip_prefix(arg_prefix)
+    flag_with_value&.delete_prefix(arg_prefix)
   end
 
   # Returns an array of values that were given as a comma-separated list.

Library/Homebrew/extend/string.rb

@@ -1,5 +1,6 @@
 # Contains backports from newer versions of Ruby
 require "backports/2.4.0/string/match"
+require "backports/2.5.0/string/delete_prefix"
 
 class String
   # String.chomp, but if result is empty: returns nil instead.
@@ -8,10 +9,6 @@ class String
     s = chomp
     s unless s.empty?
   end
-
-  def strip_prefix(prefix)
-    start_with?(prefix) ? self[prefix.length..-1] : self
-  end
 end
 
 class NilClass

Library/Homebrew/linkage_checker.rb

@@ -43,7 +43,7 @@ class LinkageChecker
     sorted.each do |dylib, files|
       puts dylib
       files.each do |f|
-        unprefixed = f.to_s.strip_prefix "#{keg}/"
+        unprefixed = f.to_s.delete_prefix "#{keg}/"
         puts "  #{unprefixed}"
       end
       puts if dylib != sorted.last.first

Library/Homebrew/tap.rb

@@ -27,7 +27,7 @@ class Tap
 
     # We special case homebrew and linuxbrew so that users don't have to shift in a terminal.
     user = user.capitalize if ["homebrew", "linuxbrew"].include? user
-    repo = repo.strip_prefix "homebrew-"
+    repo = repo.delete_prefix "homebrew-"
 
     if ["Homebrew", "Linuxbrew"].include?(user) && ["core", "homebrew"].include?(repo)
       return CoreTap.instance
@@ -119,7 +119,7 @@ class Tap
 
   def repo_var
     @repo_var ||= path.to_s
-                      .strip_prefix(TAP_DIRECTORY.to_s)
+                      .delete_prefix(TAP_DIRECTORY.to_s)
                       .tr("^A-Za-z0-9", "_")
                       .upcase
   end

Library/Homebrew/vendor/bundle-standalone/ruby/2.3.0/gems/backports-3.11.4/lib/backports/2.5.0/string/delete_prefix.rb

@@ -0,0 +1,32 @@
+unless String.method_defined? :delete_prefix
+  require 'backports/tools/arguments'
+
+  class String
+    def delete_prefix(prefix)
+      prefix = Backports.coerce_to_str(prefix)
+      if rindex(prefix, 0)
+        self[prefix.length..-1]
+      else
+        dup
+      end
+    end
+  end
+end
+
+unless String.method_defined? :delete_prefix!
+  require 'backports/tools/arguments'
+
+  class String
+    def delete_prefix!(prefix)
+      prefix = Backports.coerce_to_str(prefix)
+      chomp! if frozen?
+      len = prefix.length
+      if len > 0 && rindex(prefix, 0)
+        self[0...prefix.length] = ''
+        self
+      else
+        nil
+      end
+    end
+  end
+end

Library/Homebrew/vendor/bundle-standalone/ruby/2.3.0/gems/backports-3.11.4/lib/backports/tools/arguments.rb

@@ -0,0 +1,69 @@
+module Backports
+  # Helper method to coerce a value into a specific class.
+  # Raises a TypeError if the coercion fails or the returned value
+  # is not of the right class.
+  # (from Rubinius)
+  def self.coerce_to(obj, cls, meth)
+    return obj if obj.kind_of?(cls)
+
+    begin
+      ret = obj.__send__(meth)
+    rescue Exception => e
+      raise TypeError, "Coercion error: #{obj.inspect}.#{meth} => #{cls} failed:\n" \
+                       "(#{e.message})"
+    end
+    raise TypeError, "Coercion error: obj.#{meth} did NOT return a #{cls} (was #{ret.class})" unless ret.kind_of? cls
+    ret
+  end
+
+  def self.coerce_to_int(obj)
+    coerce_to(obj, Integer, :to_int)
+  end
+
+  def self.coerce_to_ary(obj)
+    coerce_to(obj, Array, :to_ary)
+  end
+
+  def self.coerce_to_str(obj)
+    coerce_to(obj, String, :to_str)
+  end
+
+  def self.coerce_to_hash(obj)
+    coerce_to(obj, Hash, :to_hash)
+  end
+
+  def self.coerce_to_options(obj, *options)
+    hash = coerce_to_hash(obj)
+    hash.values_at(*options)
+  end
+
+  def self.coerce_to_option(obj, option)
+    coerce_to_options(obj, option)[0]
+  end
+
+  def self.is_array?(obj)
+    coerce_to(obj, Array, :to_ary) if obj.respond_to? :to_ary
+  end
+
+  def self.try_convert(obj, cls, meth)
+    return obj if obj.kind_of?(cls)
+    return nil unless obj.respond_to?(meth)
+    ret = obj.__send__(meth)
+    raise TypeError, "Coercion error: obj.#{meth} did NOT return a #{cls} (was #{ret.class})" unless ret.nil? || ret.kind_of?(cls)
+    ret
+  end
+
+  # Checks for a failed comparison (in which case it throws an ArgumentError)
+  # Additionally, it maps any negative value to -1 and any positive value to +1
+  # (from Rubinius)
+  def self.coerce_to_comparison(a, b, cmp = (a <=> b))
+    raise ArgumentError, "comparison of #{a} with #{b} failed" if cmp.nil?
+    return 1 if cmp > 0
+    return -1 if cmp < 0
+    0
+  end
+
+  # Used internally to make it easy to deal with optional arguments
+  # (from Rubinius)
+  Undefined = Object.new
+end