update m1
Add examples of a

  - add this and that
  - and the other oe
add feature a

  - add this and that
  - and the other oe

update a1,a2

  - add important feature fixes
  - add another fix
merge
Add B feature
add b1,b2
  - add b1
  - add b2

Edit b1,b2

  - edit b1
  - edit b2
Add c1,c2

  - add c1
  - add c2
Edit c1, c2

  - edit c1 ...
  - edit c2 ...
Add d1,d2

  - add d1
  - add  d2
Edit d1, d2

  - edit d1
  - edit d2