deprecate SHA1

Library/Homebrew/checksum.rb

@@ -2,7 +2,7 @@ class Checksum
   attr_reader :hash_type, :hexdigest
   alias_method :to_s, :hexdigest
 
-  TYPES = [:sha1, :sha256]
+  TYPES = [:sha256]
 
   def initialize(hash_type, hexdigest)
     @hash_type = hash_type

Library/Homebrew/compat.rb

@@ -5,6 +5,7 @@ require "compat/formula_specialties"
 require "compat/hardware"
 require "compat/macos"
 require "compat/md5"
+require "compat/sha1"
 require "compat/requirements"
 require "compat/version"
 require "compat/download_strategy"

Library/Homebrew/compat/sha1.rb

@@ -0,0 +1,35 @@
+class Formula
+  def self.sha1(val)
+    stable.sha1(val)
+  end
+end
+
+class SoftwareSpec
+  def sha1(val)
+    @resource.sha1(val)
+  end
+end
+
+class Resource
+  def sha1(val)
+    @checksum = Checksum.new(:sha1, val)
+  end
+end
+
+class BottleSpecification
+  def sha1(val)
+    digest, tag = val.shift
+    collector[tag] = Checksum.new(:sha1, digest)
+  end
+end
+
+class Pathname
+  def sha1
+    require "digest/sha1"
+    opoo <<-EOS.undent
+    SHA1 support is deprecated and will be removed in a future version.
+    Please switch this formula to SHA256.
+    EOS
+    incremental_hash(Digest::SHA1)
+  end
+end

Library/Homebrew/extend/pathname.rb

@@ -300,12 +300,6 @@ class Pathname
     digest.hexdigest
   end
 
-  # @private
-  def sha1
-    require "digest/sha1"
-    incremental_hash(Digest::SHA1)
-  end
-
   def sha256
     require "digest/sha2"
     incremental_hash(Digest::SHA2)