This reveals it to be a bit of a mess.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
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
-------------------