FormulaInstaller: reset git_available? when installing git

Closes Homebrew/homebrew#43693

Signed-off-by: Xu Cheng <xucheng@me.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/Library/Homebrew/formula_installer.rb b/Library/Homebrew/formula_installer.rb
index fb2c023d2..f9c1ae42a 100644
--- a/Library/Homebrew/formula_installer.rb
+++ b/Library/Homebrew/formula_installer.rb
@@ -451,6 +451,9 @@ class FormulaInstaller
 
     ohai "Summary" if verbose? || show_summary_heading?
     puts summary
+
+    # let's reset Utils.git_available? if we just installed git
+    Utils.clear_git_available_cache if formula.name == "git"
   ensure
     unlock
   end
diff --git a/Library/Homebrew/utils/git.rb b/Library/Homebrew/utils/git.rb
index 10dbc83c1..74ad49ffe 100644
--- a/Library/Homebrew/utils/git.rb
+++ b/Library/Homebrew/utils/git.rb
@@ -21,5 +21,11 @@ module Utils
     rescue
       raise "Git is unavailable"
     end
+
+    raise "Git is unavailable" unless git_available?
+  end
+
+  def self.clear_git_available_cache
+    remove_instance_variable(:@git) if instance_variable_defined?(:@git)
   end
 end