Understanding merged and branches updated

I have merged changes to Understanding content to the master branch for 
publication, and "back-merged" the master branch into the working 
branches so they are up to date. In the process I changed some working 
branches:

  * purpose-of-controls is now identify-common-purpose
  * contextual-information is now identify-purpose
  * graphics-contrast is now non-text-contrast

If you are working in one of the changed branches, you will need to use 
the new branch now. If you have a clone of the repository, you should 
delete your local copy of the old branch name, to reduce the chance of 
working in the incorrect branch.

I had to sort out a lot of conflicts in this process. To reduce this, 
please:

  * Only work on the understanding file with the same name as the
    branch. Do not work on other files; if there is a need to do so, you
    should create a specialized branch.
  * For Understanding content, do not work in branches other than the
    designated branch in the wiki page
    https://www.w3.org/WAI/GL/wiki/Accepted_WCAG_2.1_SC, unless you
    explicitly intend to request merge of that branch into the
    designated branch later. Until that side branch is merged, you
    should consider its content unknown to the editors and the WG.
  * Please do not change the wiki page to reference an alternate branch
    you are using; there is a system to all this and doing so introduces
    confusion and error.
  * Do not work in forks. Forks mean different people are working in
    different places, and content is sure to get out of sync. Nobody in
    the WG should need to use a fork; if you do not have access to the
    wcag21 repository, contact me. If you absolutely must use a fork for
    some reason, make sure to sync the fork frequently, and submit pull
    requests against the designated working branch, *not* against the
    master branch.

I will tighten up editing procedures and documentation as much as I can, 
but please help me out by using the above practices.

Michael