Fix ExternalProject test failures on dashboards.

Double quote executable names that may have spaces in them.
Do not run the new git portions of the test on machines that
have git < version 1.6.5 on them.

Tests/ExternalProject/CMakeLists.txt

@@ -161,7 +161,7 @@ if(do_cvs_tests)
     SOURCE_DIR ${local_cvs_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/cvsrepo.tgz
     BUILD_COMMAND ""
-    CONFIGURE_COMMAND ${CVS_EXECUTABLE} --version
+    CONFIGURE_COMMAND "${CVS_EXECUTABLE}" --version
     INSTALL_COMMAND ""
   )
 
@@ -257,7 +257,7 @@ if(do_svn_tests)
     SOURCE_DIR ${local_svn_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/svnrepo.tgz
     BUILD_COMMAND ""
-    CONFIGURE_COMMAND ${Subversion_SVN_EXECUTABLE} --version
+    CONFIGURE_COMMAND "${Subversion_SVN_EXECUTABLE}" --version
     INSTALL_COMMAND ""
   )
 
@@ -304,6 +304,19 @@ set(do_git_tests 0)
 
 if(git_EXECUTABLE)
   set(do_git_tests 1)
+
+  execute_process(
+    COMMAND "${git_EXECUTABLE}" --version
+    OUTPUT_VARIABLE ov
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    )
+  string(REGEX REPLACE "^git version (.+)$" "\\1" git_version "${ov}")
+  message(STATUS "git_version='${git_version}'")
+
+  if(git_version VERSION_LESS 1.6.5)
+    message(STATUS "No ExternalProject git tests with git client less than version 1.6.5")
+    set(do_git_tests 0)
+  endif()
 endif()
 
 
@@ -318,7 +331,7 @@ if(do_git_tests)
     SOURCE_DIR ${local_git_repo}
     URL ${CMAKE_CURRENT_SOURCE_DIR}/gitrepo.tgz
     BUILD_COMMAND ""
-    CONFIGURE_COMMAND ${git_EXECUTABLE} --version
+    CONFIGURE_COMMAND "${git_EXECUTABLE}" --version
     INSTALL_COMMAND ""
   )