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.
 
 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
 -------------------
 
 Substitution syntax
 -------------------