docs: Summarise directory reference syntaxes

This reveals it to be a bit of a mess.

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

diff --git a/README b/README
index 1111dcb90fb7ce57ed7acd70bbe0bbbb8f275baa..5897e308644050ec8006fe42e830816ed03f0fb2 100644 (file)
--- a/README
+++ b/README
@@ -138,6 +138,19 @@ If you `include subdirmk/regen.mk', dependency management and
 automatic regeneration for all of this template substitution, and for
 config.status etc. is done for you.
 
+Summary of directory reference syntaxes
+---------------------------------------
+
+                  In source tree             In build tree
+                  Relative     Absolute      Relative  Absolute
+
+                                             &file     $(abs)/&file
+ This directory   &^/file      &~/file       &/file    $(abs)/&/file
+                  & ^ f g h    & ~ f g h     & f g h
+
+ Top level        $(ts)/file   $(ats)/file   file      $(abs)/file
+                                             f g h
+
 Substitution syntax
 -------------------