Run git operations in parallel to speed things up:

bundler/lib/bundler/definition.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require_relative "lockfile_parser"
+require_relative "worker"
 
 module Bundler
   class Definition
@@ -1100,7 +1101,23 @@ def source_requirements
       @source_requirements ||= find_source_requirements
     end
 
+    def preload_git_source_worker
+      @preload_git_source_worker ||= Bundler::Worker.new(5, "Git source preloading", ->(source, _) { source.specs })
+    end
+
+    def preload_git_sources
+      sources.git_sources.each {|source| preload_git_source_worker.enq(source) }
+    ensure
+      preload_git_source_worker.stop
+    end
+
     def find_source_requirements
+      if Gem.ruby_version >= "3.3"
+        # Ruby 3.2 has a bug that incorrectly triggers a circular dependency warning. This version will continue to
+        # fetch git repositories one by one.
+        preload_git_sources
+      end
+
       # Record the specs available in each gem's source, so that those
       # specs will be available later when the resolver knows where to
       # look for that gemspec (or its dependencies)

bundler/lib/bundler/ui/shell.rb

@@ -17,6 +17,7 @@ def initialize(options = {})
         @level = ENV["DEBUG"] ? "debug" : "info"
         @warning_history = []
         @output_stream = :stdout
+        @thread_safe_logger_key = "logger_level_#{object_id}"
       end
 
       def add_color(string, *color)
@@ -97,11 +98,13 @@ def level=(level)
       end
 
       def level(name = nil)
-        return @level unless name
+        current_level = Thread.current.thread_variable_get(@thread_safe_logger_key) || @level
+        return current_level unless name
+
         unless index = LEVELS.index(name)
           raise "#{name.inspect} is not a valid level"
         end
-        index <= LEVELS.index(@level)
+        index <= LEVELS.index(current_level)
       end
 
       def output_stream=(symbol)
@@ -167,12 +170,13 @@ def word_wrap(text, line_width = Thor::Terminal.terminal_width)
         end * "\n"
       end
 
-      def with_level(level)
-        original = @level
-        @level = level
+      def with_level(desired_level)
+        old_level = level
+        Thread.current.thread_variable_set(@thread_safe_logger_key, desired_level)
+
         yield
       ensure
-        @level = original
+        Thread.current.thread_variable_set(@thread_safe_logger_key, old_level)
       end
 
       def with_output_stream(symbol)

bundler/spec/bundler/ui/shell_spec.rb

@@ -81,4 +81,32 @@
       end
     end
   end
+
+  describe "threads" do
+    it "is thread safe when using with_level" do
+      stop_thr1 = false
+      stop_thr2 = false
+
+      expect(subject.level).to eq("debug")
+
+      thr1 = Thread.new do
+        subject.silence do
+          sleep(0.1) until stop_thr1
+        end
+
+        stop_thr2 = true
+      end
+
+      thr2 = Thread.new do
+        subject.silence do
+          stop_thr1 = true
+          sleep(0.1) until stop_thr2
+        end
+      end
+
+      [thr1, thr2].each(&:join)
+
+      expect(subject.level).to eq("debug")
+    end
+  end
 end

bundler/spec/commands/ssl_spec.rb

@@ -16,16 +16,17 @@
       end
     end
 
-    @previous_level = Bundler.ui.level
-    Bundler.ui.instance_variable_get(:@warning_history).clear
-    @previous_client = Gem::Request::ConnectionPools.client
+    @previous_ui = Bundler.ui
+    Bundler.ui = Bundler::UI::Shell.new
     Bundler.ui.level = "info"
+
+    @previous_client = Gem::Request::ConnectionPools.client
     Artifice.activate_with(@dummy_endpoint)
     Gem::Request::ConnectionPools.client = Gem::Net::HTTP
   end
 
   after(:each) do
-    Bundler.ui.level = @previous_level
+    Bundler.ui = @previous_ui
     Artifice.deactivate
     Gem::Request::ConnectionPools.client = @previous_client
   end