Adds file option to config_set to allow adding to specific git-config files

lib/git/base.rb

@@ -137,13 +137,14 @@ def chdir # :yields: the Git::Path
 
     #g.config('user.name', 'Scott Chacon') # sets value
     #g.config('user.email', 'email@email.com')  # sets value
+    #g.config('user.email', 'email@email.com', file: 'path/to/custom/config)  # sets value in file
     #g.config('user.name')  # returns 'Scott Chacon'
     #g.config # returns whole config hash
-    def config(name = nil, value = nil)
-      if(name && value)
+    def config(name = nil, value = nil, options = {})
+      if name && value
         # set value
-        lib.config_set(name, value)
-      elsif (name)
+        lib.config_set(name, value, options)
+      elsif name
         # return value
         lib.config_get(name)
       else

lib/git/lib.rb

@@ -583,8 +583,12 @@ def show(objectish=nil, path=nil)
 
     ## WRITE COMMANDS ##
 
-    def config_set(name, value)
-      command('config', name, value)
+    def config_set(name, value, options = {})
+      if options[:file].to_s.empty?
+        command('config', name, value)
+      else
+        command('config', '--file', options[:file], name, value)
+      end
     end
 
     def global_config_set(name, value)

tests/units/test_config.rb

@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby
 
-require File.dirname(__FILE__) + '/../test_helper'
+require_relative '../test_helper'
 
 class TestConfig < Test::Unit::TestCase
   def setup
@@ -26,7 +26,20 @@ def test_set_config
       g.config('user.name', 'bully')
       assert_equal('bully', g.config('user.name'))
     end
-  end  
+  end
+
+  def test_set_config_with_custom_file
+    in_temp_dir do |_path|
+      custom_config_path = "#{Dir.pwd}/bare/.git/custom-config"
+      g = Git.clone(@wbare, 'bare')
+      assert_not_equal('bully', g.config('user.name'))
+      g.config('user.name', 'bully', file: custom_config_path)
+      assert_not_equal('bully', g.config('user.name'))
+      g.config('include.path', custom_config_path)
+      assert_equal('bully', g.config('user.name'))
+      assert_equal("[user]\n\tname = bully\n", File.read(custom_config_path))
+    end
+  end
 
   def test_env_config
     with_custom_env_variables do