Move `repo_var` method to `Tap` class.

Library/Homebrew/cmd/update-report.rb

@@ -327,11 +327,11 @@ class Reporter
   def initialize(tap)
     @tap = tap
 
-    initial_revision_var = "HOMEBREW_UPDATE_BEFORE#{repo_var}"
+    initial_revision_var = "HOMEBREW_UPDATE_BEFORE#{tap.repo_var}"
     @initial_revision = ENV[initial_revision_var].to_s
     raise ReporterRevisionUnsetError, initial_revision_var if @initial_revision.empty?
 
-    current_revision_var = "HOMEBREW_UPDATE_AFTER#{repo_var}"
+    current_revision_var = "HOMEBREW_UPDATE_AFTER#{tap.repo_var}"
     @current_revision = ENV[current_revision_var].to_s
     raise ReporterRevisionUnsetError, current_revision_var if @current_revision.empty?
   end
@@ -531,13 +531,6 @@ class Reporter
 
   private
 
-  def repo_var
-    @repo_var ||= tap.path.to_s
-                     .strip_prefix(Tap::TAP_DIRECTORY.to_s)
-                     .tr("^A-Za-z0-9", "_")
-                     .upcase
-  end
-
   def diff
     Utils.popen_read(
       "git", "-C", tap.path, "diff-tree", "-r", "--name-status", "--diff-filter=AMDR",

Library/Homebrew/tap.rb

@@ -111,6 +111,13 @@ class Tap
     "https://github.com/#{full_name}"
   end
 
+  def repo_var
+    @repo_var ||= path.to_s
+                      .strip_prefix(TAP_DIRECTORY.to_s)
+                      .tr("^A-Za-z0-9", "_")
+                      .upcase
+  end
+
   # True if this {Tap} is a git repository.
   def git?
     path.git?

Library/Homebrew/test/cmd/update-report_spec.rb

@@ -20,8 +20,8 @@ describe Reporter do
       def initialize(tap)
         @tap = tap
 
-        ENV["HOMEBREW_UPDATE_BEFORE#{repo_var}"] = "12345678"
-        ENV["HOMEBREW_UPDATE_AFTER#{repo_var}"] = "abcdef00"
+        ENV["HOMEBREW_UPDATE_BEFORE#{tap.repo_var}"] = "12345678"
+        ENV["HOMEBREW_UPDATE_AFTER#{tap.repo_var}"] = "abcdef00"
 
         super(tap)
       end