Bug#776251: ack-grep fails to install due to diversion problem

[Olivier Schwander]

Package: ack-grep
Version: 2.14-4
Severity: grave
Justification: renders package unusable

ack-grep fails to install pretending `/usr/bin/ack' is diverted by
`/usr/bin/ack-grep' although the /usr/bin/ack file does not exist:

$ apt-get install ack-grep
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed:
  ack-grep
0 upgraded, 1 newly installed, 0 to remove and 40 not upgraded.
Need to get 0 B/67.0 kB of archives.
After this operation, 236 kB of additional disk space will be used.
(Reading database ... 463241 files and directories currently installed.)
Preparing to unpack .../ack-grep_2.14-4_all.deb ...
Unpacking ack-grep (2.14-4) ...
dpkg: error processing archive /var/cache/apt/archives/ack-grep_2.14-4_all.deb (--unpack):
 trying to overwrite `/usr/bin/ack', which is the diverted version of `/usr/bin/ack-grep'
Processing triggers for man-db (2.7.0.2-5) ...
Errors were encountered while processing:
 /var/cache/apt/archives/ack-grep_2.14-4_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
zsh: exit 100   apt-get install ack-grep

It works well after manullay removing the diversion:

$ dpkg-divert --list "*ack*"
local diversion of /usr/bin/ack-grep to /usr/bin/ack
$ dpkg-divert --remove /usr/bin/ack-grep
Removing 'local diversion of /usr/bin/ack-grep to /usr/bin/ack'

I do not understand why the diversion is still there: if I remember well,
the ack-grep package was installed on this system, then removed. The
installation of the package works well on a freshly bootstrapped debian sid.

Besides, I am not sure the diversion is still needed, since according to
apt-file, ack-grep is the only package providing /usr/bin/ack.

Thanks

-- System Information:
Debian Release: 8.0
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386, armel, armhf

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages ack-grep depends on:
ii  libfile-next-perl  1.12-1
ii  perl               5.20.1-4

ack-grep recommends no packages.

ack-grep suggests no packages.

-- no debconf information