blackbox: adds a 'blackbox' command for viewing recent logs
Adds a 'hg blackbox' command for viewing the latest entries in the blackbox log.
By default it shows the last 10 entries, but -l allows the user to specify.
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ ls
a
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
B should disappear
$ ls
a