Documentation: Split description of pretty formats of commit log
Split description of pretty formats into list of pretty options
(--pretty and --encoding) in new file Documentation/pretty-options.txt
and description of formats itself as a separate "PRETTY FORMATS"
section in pretty-formats.txt
While at it correct formatting a bit, to be better laid out in the
resulting manpages: git-rev-list(1), git-show(1), git-log(1) and
git-diff-tree(1). Those manpages now include pretty options in the
same place as it was before, and description of formats just after
all options.
Signed-off-by: Jakub Narebski <jnareb@gmail.com>