aportgen: fix fork_alpine related error (!1815)

Make sure, that "args.fork_alpine" is always present. Otherwise,
pmbootstrap will fail if the aportgen code is called by anything but
"pmbootstrap aportgen". For example, when the user is adding a new
device during "pmbootstrap init".

Fixes: 54e51759ad ("aportgen: add feature to fork upstream packages")

pmb/config/__init__.py

@@ -66,6 +66,7 @@ defaults = {
     "config": os.path.expanduser("~") + "/.config/pmbootstrap.cfg",
     "device": "samsung-i9100",
     "extra_packages": "none",
+    "fork_alpine": False,
     "hostname": "",
     # A higher value is typically desired, but this can lead to VERY long open
     # times on slower devices due to host systems being MUCH faster than the

test/test_aportgen_device_wizard.py

@@ -35,7 +35,6 @@ def args(tmpdir, request):
     sys.argv = ["pmbootstrap.py", "build", "-i", "device-testsuite-testdevice"]
     args = pmb.parse.arguments()
     args.log = args.work + "/log_testsuite.txt"
-    args.fork_alpine = False
     pmb.helpers.logging.init(args)
     request.addfinalizer(args.logfd.close)