Merge branch 'js/branch-track'

* js/branch-track:
  doc: documentation update for the branch track changes
  branch: optionally setup branch.*.merge from upstream local branches

Conflicts:

	Documentation/config.txt
	Documentation/git-branch.txt
	Documentation/git-checkout.txt
	builtin-branch.c
	cache.h
	t/t7201-co.sh

environment.c

@@ -37,6 +37,7 @@ const char *excludes_file;
 int auto_crlf = 0;	/* 1: both ways, -1: only when adding git objects */
 enum safe_crlf safe_crlf = SAFE_CRLF_WARN;
 unsigned whitespace_rule_cfg = WS_DEFAULT_RULE;
+enum branch_track git_branch_track = BRANCH_TRACK_REMOTE;
 
 /* This is set by setup_git_dir_gently() and/or git_default_config() */
 char *git_work_tree_cfg;