bash completion: Add completion for 'git help'
bash completion: Add completion for 'git help'

Rename cached __git_commandlist to __git_porcelain_commandlist and
add __git_all_commandlist that only filters out *--* helpers.

Completions for 'git help' will use the __git_all_commandlist, while
the __git_porcelain_commandlist is used for git command completion.

Users who actually read man pages may want to see help for plumbing
commands.

Signed-off-by: Lee Marlow <c895bdfdd1bf99084d7efdbd77c43126cd4b21a6@gmail.com>
Acked-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git