help: respect new common command grouping

help: respect new common command grouping

'git help' shows common commands in alphabetical order:

The most commonly used git commands are:
   add        Add file contents to the index
   bisect     Find by binary search the change that introduced a bug
   branch     List, create, or delete branches
   checkout   Checkout a branch or paths to the working tree
   clone      Clone a repository into a new directory
   commit     Record changes to the repository
   [...]

without any indication of how commands relate to high-level
concepts or each other. Revise the output to explain their relationship
with the typical Git workflow:

  These are common Git commands used in various situations:

  start a working area (see also: git help tutorial)
     clone      Clone a repository into a new directory
     init       Create an empty Git repository or reinitialize [...]

  work on the current change (see also: git help everyday)
     add        Add file contents to the index
     reset      Reset current HEAD to the specified state

  examine the history and state (see also: git help revisions)
     log        Show commit logs
     status     Show the working tree status

     [...]

Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Sébastien Guimmara <sebastien.guimmara@gmail.com>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>