PATCH: dpkg: allow missing /etc/dpkg/dpkg.d directory

[Anders Oleson <anders@openpuma.org>]

This is a request to upstream a patch that I am proposing to the Yocto /
OpenEmbedded core projects. In the context of those projects, dpkg is run in
an unusual environment for cross-development/installs. In this environment the
location of what is normally the /etc/dpkg/dpkg.d directory can, in unusual
circumstances be invalid. The other important paths are all passed as command
line parameters instead.

This patch removes the error and message when /etc/dpkg/dpkg.d is missing and
instead acts the same as if it were empty. This works around the conditions
where the directory may be missing in an predictable sysroot cross
environment. It appears that this directory is often empty, so there seems
little reason to provide an error if the directory itself is missing in the
first place.

Text of the Yocto/OE patch email below:

The dpkg binary contains a hard-coded CONFIGDIR path which normally points to
/etc/dpkg. However, if /etc/dpkg/dpkg.cfg.d doesn't exist (ENOTDIR) it fails
with an error, even though it does not fail when the directory exists but is
empty (ENOENT).

Normally this is not an issue, but when dpkg-native is built, CONFIGDIR
points to a directory in the sysroot under work. If that binary is later
cached in the sstate-cache and mirrored to another host that does not contain
the same work directory, the dpkg binary fails due to this missing directory
during certain packaging steps involving apt-get. This "leaks" information
about the build host into the sstate-cache in an unintended way that causes a
failure.

The dpkg utility does not currently allow a command line or environment
override of CONFIGDIR, so this patches dpkg so that a missing directory is the
same as an empty one and the failure is avoided. The dpkg-native is always
passed command line arguments and does not need, nor contain, any
configuration data in this directory in the first place.

Signed-off-by: Anders Oleson <anders@openpuma.org>

Index: dpkg-1.18.7/lib/dpkg/options.c
===================================================================
--- dpkg-1.18.7.orig/lib/dpkg/options.c
+++ dpkg-1.18.7/lib/dpkg/options.c
@@ -172,11 +172,8 @@ dpkg_options_load_dir(const char *prog,

   dlist_n = scandir(dirname, &dlist, valid_config_filename, alphasort);
   if (dlist_n < 0) {
-    if (errno == ENOENT) {
       free(dirname);
       return;
-    } else
-      ohshite(_("error opening configuration directory '%s'"), dirname);
   }

   for (i = 0; i < dlist_n; i++) {