Perform the CTest Update Step as a Dashboard Client.

ctest_update([SOURCE <source-dir>]
             [RETURN_VALUE <result-var>]
             [CAPTURE_CMAKE_ERROR <result-var>]

Update the source tree from version control and record results in Update.xml for submission with the ctest_submit() command.

The options are:

SOURCE <source-dir>
Specify the source directory. If not given, the CTEST_SOURCE_DIRECTORY variable is used.
RETURN_VALUE <result-var>
Store in the <result-var> variable the number of files updated or -1 on error.
Store in the <result-var> variable -1 if there are any errors running the command and prevent ctest from returning non-zero if an error occurs.
Tell CTest to suppress most non-error messages that it would have otherwise printed to the console. CTest will still report the new revision of the repository and any conflicting files that were found.

The update always follows the version control branch currently checked out in the source directory. See the CTest Update Step documentation for more information.