From 8ffc77d8e89ebb1e4895b1d4927f713f182cac66 Mon Sep 17 00:00:00 2001
From: Markus Reiter <me@reitermark.us>
Date: Sat, 3 Jun 2017 00:23:06 +0200
Subject: [PATCH] Refactor `formula_at_revision`.

---
 Library/Homebrew/formula_versions.rb | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/Library/Homebrew/formula_versions.rb b/Library/Homebrew/formula_versions.rb
index dda8dc7126..bb68035679 100644
--- a/Library/Homebrew/formula_versions.rb
+++ b/Library/Homebrew/formula_versions.rb
@@ -17,6 +17,7 @@ class FormulaVersions
     @repository = formula.tap.path
     @entry_name = @path.relative_path_from(repository).to_s
     @current_formula = formula
+    @formula_at_revision = {}
   end
 
   def rev_list(branch)
@@ -32,20 +33,20 @@ class FormulaVersions
   end
 
   def formula_at_revision(rev)
-    contents = file_contents_at_revision(rev)
+    Homebrew.raise_deprecation_exceptions = true
 
-    begin
-      Homebrew.raise_deprecation_exceptions = true
-      yield nostdout { Formulary.from_contents(name, path, contents) }
-    rescue *IGNORED_EXCEPTIONS => e
-      # We rescue these so that we can skip bad versions and
-      # continue walking the history
-      ohai "#{e} in #{name} at revision #{rev}", e.backtrace if ARGV.debug?
-    rescue FormulaUnavailableError
-      # Suppress this error
-    ensure
-      Homebrew.raise_deprecation_exceptions = false
+    yield @formula_at_revision[rev] ||= begin
+      contents = file_contents_at_revision(rev)
+      nostdout { Formulary.from_contents(name, path, contents) }
     end
+  rescue *IGNORED_EXCEPTIONS => e
+    # We rescue these so that we can skip bad versions and
+    # continue walking the history
+    ohai "#{e} in #{name} at revision #{rev}", e.backtrace if ARGV.debug?
+  rescue FormulaUnavailableError
+    # Suppress this error
+  ensure
+    Homebrew.raise_deprecation_exceptions = false
   end
 
   def bottle_version_map(branch)