Do not require $srctree to be set for non-kernel projects.

(It was never required if you explicitly passed a 'base_dir', but it's a
bit silly to have to do that too.)

This is a bug. I expected os.path.expandvars() to replace references
non-set environment variables with nothing, but it leaves them as is.

Work around it by letting base_dir = None be special and the default. It
uses $srctree if set and the current directory otherwise. This has the
following advantages:

 - It avoids having to reimplement a different version of
   os.path.expandvars() and special-casing "" to mean the current
   directory.

 - It means '$' can appear in paths. (Though it probably never will.)

Maybe the expansion behavior could be removed too, but keep it for now
to be backwards compatible.

1 files changed, 2 insertions, 0 deletions

diff --git a/tests/Kbase_dir b/tests/Kbase_dir
new file mode 100644
index 0000000..9f8c55a
--- /dev/null
+++ b/tests/Kbase_dir
@@ -0,0 +1,2 @@
+# This will only work if 'base_dir' is set correctly
+source "empty"