README: Explain a wrinkle in &:include filename semantics

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/README b/README
index c4f9d0ea484881aba7058c604482957b948e727a..b812f2782b06557d43101f1a642ebdf65570a018 100644 (file)
--- a/README
+++ b/README
@@ -235,8 +235,11 @@ So pathname syntax is a subset of:
 
 &:include filename             filename should usually be [&]foo.sd.mk
 &:-include filename            tolerate nonexistent file
-       filenames are relative to $(top_srcdir)
-       RHS is &-expanded
+       RHS is &-expanded but filenames are relative to the top
+       srcdir.  This implies that unqualified names are like &~/
+       whereas &/ is like &^/.  &^ and &~ do not work here because
+       they expand to constructions involving literally
+       `$(top_srcdir)', but the RHS is not make-expanded.
 
 &!<lwsp>       disables & until EOL (and then disappears)