[PATCH/WIP 0/9] for-each-ref format improvements

The purpose of this series is to make "for-each-ref --format" powerful enough to display what "branch -v" and "branch -vv" do so that we could get rid of those display code and use for-each-ref code instead.

The benefits are clear: share more code, branch can also borrow --sort and --format from for-each-ref, which should satisty users who are not happy with what -v and -vv provides.

This version has not gotten there yet. I just want to post quick and dirty changes and try to address some design issues.

Originally I wanted to introduce --pretty with git-log's pretty syntax to for-each-ref, deprecating --format. But because --format has to be there forever, we cannot remove its code, and the code change to make pretty code ready for displaying refs may not be small. So I went with enhancing --format syntax instead.

This series introduces:

 - %(current), which either shows "*" if the ref is pointed by HEAD
   or a space. Junio called it %(headness). I don't like that.
   I don't like %(current) either but we have to start somewhere.
   Name suggestion? %(marker)??

 - %(tracking[:upstream]) gives us the exact output that branch -v[v]
   does. %(upstream) does not include []. We can't change its
   semantics.
 
 - %(color:...) is pretty much the same as %C family in pretty code.
   I haven't added code for %(color:foo) == %C(foo) yet. There's a
   potential ambiguity here: %C(red) == %Cred or %C(red)??

 - %(...:aligned) to do left aligning. I'm not entirely sure about
   this. We might be able to share code with %>, %< and %>< from
   pretty.c. But we need improvements there too because in
   for-each-ref case, we could calculate column width but %< would
   require the user to specify the width.

   Do people expect fancy layout with for-each-ref (and branch)? If so
   we might need to have %(align) or something instead of the simple
   left alignment case in %(...:aligned)
 
 - We may need an equivalent of the space following % in pretty
   format. If the specifier produces something, then prepend a space,
   otherwise produce nothing. Do it like %C( tracking) vs
   %C(tracking)??

You can try this after applying the series, which should give you the about close to 'branch -v'. %(tracking) coloring does not work though.

git for-each-ref --format='%(current) %(color:auto)%(refname:short:aligned)%(color:reset) %%(objectname:short) %(tracking) %(subject)' 'refs/heads/*'

Nguyễn Thái Ngọc Duy (9):
  quote.c: make sq_quote_print a slight wrapper of sq_quote_buf
  for-each-ref: convert to use *_quote_buf instead of _quote_print
  for-each-ref: avoid printing each element directly to stdout
  for-each-ref: add %(current) for current branch marker
  for-each-ref: add %(tracking[:upstream]) for tracking info
  for-each-ref: add %(color:...)
  for-each-ref: prepoplulate all atoms before show_ref()
  for-each-ref: merge show_ref into show_refs
  for-each-ref: support %(...:aligned) for left alignment

 branch.h               |  11 ++++
 builtin/branch.c       |  16 ++----
 builtin/for-each-ref.c | 146 ++++++++++++++++++++++++++++++++++++++++++-------
 quote.c                |  61 +++++++++------------
 quote.h                |   6 +-
 5 files changed, 170 insertions(+), 70 deletions(-)