scm: git: add methods of getting git version and add unit lib test (#4273).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@4829 e93f8b46-1217-0410-a6f0-8f06a7374b81

lib/redmine/scm/adapters/git_adapter.rb

@@ -33,9 +33,24 @@ module Redmine
             @@sq_bin ||= shell_quote(GIT_BIN)
           end
 
+          def client_version
+            @@client_version ||= (scm_command_version || [])
+          end
+
           def client_available
             !client_version.empty?
           end
+
+          def scm_command_version
+            scm_version = scm_version_from_command_line
+            if m = scm_version.match(%r{\A(.*?)((\d+\.)+\d+)})
+              m[2].scan(%r{\d+}).collect(&:to_i)
+            end
+          end
+
+          def scm_version_from_command_line
+            shellout("#{sq_bin} --version") { |io| io.read }.to_s
+          end
         end
 
         def info