Allow tracking branches to set up rebase by default.

Change cd67e4d4 introduced a new configuration parameter that told
pull to automatically perform a rebase instead of a merge.  This
change provides a configuration option to enable this feature
automatically when creating a new branch.

If the variable branch.autosetuprebase applies for a branch that's
being created, that branch will have branch.<name>.rebase set to true.

Signed-off-by: Dustin Sallings <dustin@spy.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -434,7 +434,15 @@ enum branch_track {
 	BRANCH_TRACK_EXPLICIT,
 };
 
+enum rebase_setup_type {
+	AUTOREBASE_NEVER = 0,
+	AUTOREBASE_LOCAL,
+	AUTOREBASE_REMOTE,
+	AUTOREBASE_ALWAYS,
+};
+
 extern enum branch_track git_branch_track;
+extern enum rebase_setup_type autorebase;
 
 #define GIT_REPO_VERSION 0
 extern int repository_format_version;