Bug#844454: autopkgtest: does not apply quilt patches when running tests from source package directory

[fsfs@debian.org (Florian Schlichting)]

Package: autopkgtest
Version: 4.2
Severity: normal

When running 'autopkgtest -s -- schroot unstable-amd64-sbuild', quilt
patches are applied when building the package, but they are not applied
in tests-tree / real-tree. Those directories look just like the current
directory when issuing the autopkgtest command, possibly with just half
the quilt series applied. This is confusing, and should be changed to
apply all patches like for the build stage.

I noticed this while working on an autopkgtest-related fix to
libhttp-throwable-perl's upstream test suite (c.f. #837140), with the
above command first succeeding and then failing for an unchanged source
package...

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (990, 'testing'), (700, 'unstable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.8.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages autopkgtest depends on:
ii  apt-utils       1.3.1
ii  libdpkg-perl    1.18.14
ii  procps          2:3.3.12-2
ii  python3         3.5.1-4
ii  python3-debian  0.1.29

Versions of packages autopkgtest recommends:
ii  autodep8  0.8

Versions of packages autopkgtest suggests:
pn  lxc          <none>
pn  lxd-client   <none>
ii  qemu-system  1:2.7+dfsg-3+b1
ii  qemu-utils   1:2.7+dfsg-3+b1
ii  schroot      1.6.10-2+b2

-- no debconf information