refactoring refspecs

Changes in v2:
* added missing extern keyword in the first patch
* reordered patch 2 and 3 and updated some comments to be clearer.
* fixed some memory leaks
* squashed in some changes recommended by Aevar

Brandon Williams (36):
refspec: move refspec parsing logic into its own file
refspec: rename struct refspec to struct refspec_item
refspec: factor out parsing a single refspec
refspec: introduce struct refspec
refspec: convert valid_fetch_refspec to use parse_refspec
submodule--helper: convert push_check to use struct refspec
pull: convert get_tracking_branch to use refspec_item_init
transport: convert transport_push to use struct refspec
remote: convert check_push_refs to use struct refspec
remote: convert match_push_refs to use struct refspec
clone: convert cmd_clone to use refspec_item_init
fast-export: convert to use struct refspec
remote: convert push refspecs to struct refspec
remote: convert fetch refspecs to struct refspec
remote: remove add_prune_tags_to_fetch_refspec
transport-helper: convert to use struct refspec
fetch: convert fetch_one to use struct refspec
fetch: convert refmap to use struct refspec
refspec: remove the deprecated functions
fetch: convert do_fetch to take a struct refspec
fetch: convert get_ref_map to take a struct refspec
fetch: convert prune_refs to take a struct refspec
remote: convert get_stale_heads to take a struct refspec
remote: convert apply_refspecs to take a struct refspec
remote: convert query_refspecs to take a struct refspec
remote: convert get_ref_match to take a struct refspec
remote: convert match_explicit_refs to take a struct refspec
push: check for errors earlier
push: convert to use struct refspec
transport: convert transport_push to take a struct refspec
send-pack: store refspecs in a struct refspec
transport: remove transport_verify_remote_names
http-push: store refspecs in a struct refspec
remote: convert match_push_refs to take a struct refspec
remote: convert check_push_refs to take a struct refspec
submodule: convert push_unpushed_submodules to take a struct refspec

 Makefile                    |   1 +
 branch.c                    |   7 +-
 builtin/clone.c             |  13 +-
 builtin/fast-export.c       |  22 +--
 builtin/fetch.c             | 134 ++++++--------
 builtin/merge.c             |   1 +
 builtin/pull.c              |   9 +-
 builtin/push.c              |  80 ++++----
 builtin/remote.c            |  37 ++--
 builtin/send-pack.c         |  24 +--
 builtin/submodule--helper.c |  14 +-
 checkout.c                  |   5 +-
 http-push.c                 |  18 +-
 refspec.c                   | 194 ++++++++++++++++++++
 refspec.h                   |  44 +++++
 remote.c                    | 353 ++++++++----------------------------
 remote.h                    |  50 ++---
 submodule.c                 |  19 +-
 submodule.h                 |   3 +-
 transport-helper.c          |  39 ++--
 transport.c                 |  51 ++----
 transport.h                 |   4 +-
 22 files changed, 527 insertions(+), 595 deletions(-)
 create mode 100644 refspec.c
 create mode 100644 refspec.h

2.17.0.441.gb46fe60e1d-goog