What effect does rdiff-backup's --exclude option have on previous increments?

Question

Using rdiff-backup, a reverse-incremental backup tool, if I use the --exclude option to exclude some files that were previously included in earlier increments (older backups), what effect will it have?

Answer 1

It looks like the excluded file disappears from the latest version.

$ ls -l original/
total 0
-rw-r--r-- 1 jkiv jkiv 0 2010-11-14 16:35 a.txt
-rw-r--r-- 1 jkiv jkiv 0 2010-11-14 16:35 b.txt
-rw-r--r-- 1 jkiv jkiv 0 2010-11-14 16:35 c.txt
$ ls -l backup/
total 0
$ rdiff-backup original/ backup/
$ ls -l backup/
total 4
-rw-r--r-- 1 jkiv jkiv    0 2010-11-14 16:35 a.txt
-rw-r--r-- 1 jkiv jkiv    0 2010-11-14 16:35 b.txt
-rw-r--r-- 1 jkiv jkiv    0 2010-11-14 16:35 c.txt
drwx------ 3 jkiv jkiv 4096 2010-11-14 18:16 rdiff-backup-data
$ echo "Update for good measure." > original/a.txt 
$ rdiff-backup --exclude original/b.txt original/ backup/
$ ls -l backup/
total 8
-rw-r--r-- 1 jkiv jkiv   42 2010-11-14 18:16 a.txt
-rw-r--r-- 1 jkiv jkiv    0 2010-11-14 16:35 c.txt
drwx------ 3 jkiv jkiv 4096 2010-11-14 18:17 rdiff-backup-data