Bug#930472: lintian: systemd-service-file-missing-install-key shouldn't fire for dbus activated services

[Arnaud Rebillout <arnaud.rebillout@collabora.com>]

Package: lintian
Version: 2.15.0
Severity: normal

Dear Maintainer,

   * What led up to the situation?

I'm working on the rauc package at https://salsa.debian.org/debian/rauc/

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

I build the package, then lintian runs.

   * What was the outcome of this action?

Lintian complains about systemd-service-file-missing-install-key, and
it's true, there's no install key in the rauc.service file provided by
upstream.

   * What outcome did you expect instead?

The warning should not fire in this case.

Upstream ships a systemd service file, and a d-bus service file. The
rauc daemon is d-bus activated (meaning, it's automatically started by
the client when needed).

This use-case is described in the systemd service documentation,
https://www.freedesktop.org/software/systemd/man/systemd.service.html#id-1.10.6,
(see Example 5. DBus services).

May I quote:

    For bus-activatable services, do not include a "[Install]" section
    in the systemd service file ...

So, well, I don't know if Lintian is aware of dbus service files that
get installed at `/usr/share/dbus-1/` (I'm not familiar with lintian at
all). If so, then Lintian could look for a key `SystemdService=` in the
d-bus service file, along with `BusName=` in the systemd service file.

If both are found, Lintian shouldn't complain then about a missing
[Install] key. We could even go as far as asking Lintian to complain
about the *existence* of [Install] in this case, but maybe I'm getting
carried away...

Thanks,

  Arnaud

-- System Information:
Debian Release: 10.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 4.19.0-5-amd64 (SMP w/8 CPU cores)
Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages lintian depends on:
ii  binutils                       2.31.1-16
ii  bzip2                          1.0.6-9
ii  diffstat                       1.62-1
ii  dpkg                           1.19.6
ii  dpkg-dev                       1.19.6
ii  file                           1:5.35-4
ii  gettext                        0.19.8.1-9
ii  gpg                            2.2.12-1
ii  intltool-debian                0.35.0+20060710.5
ii  libapt-pkg-perl                0.1.34+b1
ii  libarchive-zip-perl            1.64-1
ii  libcapture-tiny-perl           0.48-1
ii  libcgi-pm-perl                 4.40-1
ii  libclass-accessor-perl         0.51-1
ii  libclone-perl                  0.41-1+b1
pn  libdigest-sha-perl             <none>
ii  libdpkg-perl                   1.19.6
ii  libemail-valid-perl            1.202-1
ii  libfile-basedir-perl           0.08-1
ii  libio-async-perl               0.72-1
ii  libipc-run-perl                20180523.0-1
ii  liblist-moreutils-perl         0.416-1+b4
ii  libparse-debianchangelog-perl  1.2.0-13
ii  libpath-tiny-perl              0.108-1
ii  libtext-levenshtein-perl       0.13-1
ii  libtimedate-perl               2.3000-2
ii  libtry-tiny-perl               0.30-1
ii  liburi-perl                    1.76-1
ii  libxml-simple-perl             2.25-1
ii  libyaml-libyaml-perl           0.76+repack-1
ii  man-db                         2.8.5-2
ii  patchutils                     0.3.4-2
ii  perl                           5.28.1-6
ii  t1utils                        1.41-3
ii  xz-utils                       5.2.4-1

Versions of packages lintian recommends:
ii  libperlio-gzip-perl  0.19-1+b5

Versions of packages lintian suggests:
pn  binutils-multiarch     <none>
ii  libhtml-parser-perl    3.72-3+b3
ii  libtext-template-perl  1.55-1

-- no debconf information