read-tree: reorganize bind_merge code.
read-tree: reorganize bind_merge code.

This does not change the logic but moves the order of checks
around so that merging of read-tree safety code would become
easier.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git