Simplify repo helper in GitSpecHelpers

Condense two separate calls to `Dir.chdir(path)` into a single call with
a block passed in.

Change-Id: I41b089981414d4f02757740e411f336d5e18102a
Reviewed-on: https://gerrit.causes.com/25222
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>

Author: Shane da Silva

spec/support/git_spec_helpers.rb

@@ -1,8 +1,10 @@
 module GitSpecHelpers
   def repo(&block)
     Dir.mktmpdir.tap do |path|
-      Dir.chdir(path) { `git init` }
-      Dir.chdir(path, &block)
+      Dir.chdir(path) do
+        `git init`
+        block.call
+      end
     end
   end