[RFC/PATCH v3 0/3] Add support for `git archive --submodules`

This series teaches read_tree_recursive() how to traverse gitlink entries when explicitly instructed to do so (by the return value from the provided callback function) and then uses this functionallity in git-archive to implement a basic --submodules option (as suggested by René in http://thread.gmane.org/gmane.comp.version-control.git/106167/focus=106235).

The commit message of the third patch has some suggestions on how the new feature may be extended to support more use cases - hopefully this will cover the issues mentioned by Johannes and Junio in the same thread.

Lars Hjemli (3):
  tree.c: teach read_tree_recursive how to traverse gitlink entries
  sha1_file: prepare for adding alternates on demand
  archive.c: add basic support for submodules

 Documentation/git-archive.txt |    3 +
 archive.c                     |   53 ++++++++++++++++++-
 archive.h                     |    1 +
 builtin-ls-tree.c             |    9 +---
 cache.h                       |    1 +
 merge-recursive.c             |    2 +-
 sha1_file.c                   |   40 +++++++++-----
 t/t5001-archive-submodules.sh |  121 +++++++++++++++++++++++++++++++++++++++++
 tree.c                        |   28 ++++++++++
 9 files changed, 236 insertions(+), 22 deletions(-)
 create mode 100755 t/t5001-archive-submodules.sh