If a patch was not mentioned in the applied/unapplied files,
"assimilate" used to ignore it. Now it won't. The only information
loss ensuing from this sequence of commands
$ rm .git/patches/<branch>/{un,}applied
$ touch .git/patches/<branch>/{un,}applied
$ stg assimilate
is now the order of the unapplied patches.
Signed-off-by: Karl Hasselström <kha@treskal.com>