[PATCH] ifupdown: Support "source-directory" stanza

[Brandon Maier]

On Mon, Oct 1, 2018 at 3:04 AM, Bernhard Reutner-Fischer
<rep.dot.nop at gmail.com> wrote:
...
> Shouldn't this use recursive_action?

I hadn't seen recursive_action() when I wrote this. Is there a set of
flags that gets us the same behavior? It looks like recursive_action
always recurses through sub-directories, but we only want to recurse
through the first directory.

I see the concat_subpath_file() helper in that function, that would be
a better way to format the filenames. I can spin a follow-on patch to
switch to that.

Also, after some further review on our end, it was pointed out that
ifupdown's source-directory silently ignores if the directory is
missing[1]. So I can include a change to switch xopendir -> opendir()
as well.

[1] https://salsa.debian.org/debian/ifupdown/blob/0.8.33/config.c#L543