#5 Indefinite growth of 'session-file-alist'

[Sergey Organov]

'session-file-alist' grows indefinitely as it includes more an more entries for the same file/buffer (intermixed with those for other files/buffers), causing menu operations to become painfully slow over time.

Restarting Emacs helps to cut it back to a sane limit.

Emacs version: GNU Emacs 24.4.1
session.el version: 2.3

Example sesstion-file-alist value:

(("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/News/nnml:support-jns.KILL" 64 nil 1 nil nil 44
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 96 273 1 nil nil 96
(overwrite-mode))
("~/fitness/workouts/osv/journals/2019_09_16-etk.txt" 9598 9591 1 nil nil 9598
(overwrite-mode))
("~/fitness/workouts/osv/journals/2019_weight.txt" 1151 1127 1 nil nil 1151
(overwrite-mode))
("~/fitness/workouts/Alexander/first.txt" 269 1 1 nil nil 274
(overwrite-mode))
("~/public/todo.txt" 28 334 1 nil nil 369
(overwrite-mode))
("~/tmp/gr" 5 nil 1 nil nil 5
(overwrite-mode))
("~/.bbdb" 19301 31 1 nil nil 19505
(overwrite-mode))
("~/tmp/var.el" 1463173 4 1 nil nil 65
(overwrite-mode)))