Merge branch 'pt/pull-builtin'

Reimplement 'git pull' in C.

* pt/pull-builtin:
  pull: remove redirection to git-pull.sh
  pull --rebase: error on no merge candidate cases
  pull --rebase: exit early when the working directory is dirty
  pull: configure --rebase via branch.<name>.rebase or pull.rebase
  pull: teach git pull about --rebase
  pull: set reflog message
  pull: implement pulling into an unborn branch
  pull: fast-forward working tree if head is updated
  pull: check if in unresolved merge state
  pull: support pull.ff config
  pull: error on no merge candidates
  pull: pass git-fetch's options to git-fetch
  pull: pass git-merge's options to git-merge
  pull: pass verbosity, --progress flags to fetch and merge
  pull: implement fetch + merge
  pull: implement skeletal builtin pull
  argv-array: implement argv_array_pushv()
  parse-options-cb: implement parse_opt_passthru_argv()
  parse-options-cb: implement parse_opt_passthru()

git.c

@@ -445,6 +445,7 @@ static struct cmd_struct commands[] = {
 	{ "pickaxe", cmd_blame, RUN_SETUP },
 	{ "prune", cmd_prune, RUN_SETUP },
 	{ "prune-packed", cmd_prune_packed, RUN_SETUP },
+	{ "pull", cmd_pull, RUN_SETUP | NEED_WORK_TREE },
 	{ "push", cmd_push, RUN_SETUP },
 	{ "read-tree", cmd_read_tree, RUN_SETUP },
 	{ "receive-pack", cmd_receive_pack },