Re: [PATCH] completion: clarify support for short options and arguments

Junio C Hamano [off-list ref] writes:

The list of supported completions in the header of the file was
mostly written a long time ago when Shawn added the initial version
of this script in 2006.  The list explicitly states that we complete
"common --long-options", which implies that we do not complete
not-so-common ones and single letter options (this text dates back
to May 2007).

Update the description to explicitly state that single-letter
options are not completed.  Also, document that arguments to options
are completed, even for single-letter options (e.g., "git -c <TAB>"
offers configuration variables).

I appended the following to the end of the proposed commit log
message:

  The reason why we do not complete single-letter options is because
  it does not seem to help all that much to learn that the command
  takes -c, -d, -e options when "git foo -<TAB>" offers these three,
  unlike long options that is easier to guess what they are about.

  Because this rationale is primarily for our developers, let's leave
  it out of the completion script itself, whose messages are entirely
  for end-users.  Our developers can run "git blame" to find this
  commit as needed.