Documentation: add shell guidelines
Add the following guideline to Documentation/CodingGuidelines:
Break overlong lines after "&&", "||", and "|", not before
them; that way the command can continue to subsequent lines
without backslash at the end.
And the following to t/README (since it is specific to writing tests):
Pipes and $(git ...) should be avoided when they swallow exit
codes of Git processes
Signed-off-by: Matthew DeVore <matvore@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>