Teach (create|run)_dashboard_script macros to treat the argument as the
name of a build tree. Append '.cmake' to generate the dashboard script
name. This allows future re-use of the macros for multiple test
scripts.
This creates cmCTestHG to drive CTest Update handling on hg-based work
trees. Currently we always update to the head of the remote tracking
branch (hg pull), so the nightly start time is ignored for Nightly
builds. A later change will address this.
See issue #7879. Patch from Emmanuel Christophe. I modified the patch
slightly for code style, to finish up some parsing details, and to fix
the test.