Merge branch 'sg/help-group'

Group list of commands shown by "git help" along the workflow
elements to help early learners.

* sg/help-group:
  help: respect new common command grouping
  command-list.txt: drop the "common" tag
  generate-cmdlist: parse common group commands
  command-list.txt: add the common groups block
  command-list: prepare machinery for upcoming "common groups" section

diff --cc Makefile
Simple merge