docs: New plan for directory references, further

[subdirmk.git] / README

diff --git a/README b/README
index 5897e308644050ec8006fe42e830816ed03f0fb2..3059d9a105cfb57a9071a4da0f50e9cc19783a62 100644 (file)
--- a/README
+++ b/README
@@ -138,18 +138,32 @@ 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
----------------------------------------
+Summary of recommended directory reference syntaxes
+---------------------------------------------------
 
-                  In source tree             In build tree
-                  Relative     Absolute      Relative  Absolute
+Path construction &-expansions, meanings summary:
 
-                                             &file     $(abs)/&file
- This directory   &^/file      &~/file       &/file    $(abs)/&/file
-                  & ^ f g h    & ~ f g h     & f g h
+                      In build tree            In source tree
+  This directory      just &                   &,
+  Top level           &.  implies absolute     &;
 
- Top level        $(ts)/file   $(ats)/file   file      $(abs)/file
-                                             f g h
+Adding `@' means "absolute path".  This is not needed with &. because
+there is never any need to use &. since it would expand to nothing.
+`/' terminates the escape (needed if the next thing is not a lowercase
+character, or space).  `=' means "just the value, no /".  Space starts
+multi-word processing.
+
+      Recommended     In build tree             In source tree
+             when     Relative  Absolute        Relative     Absolute
+                                          
+  This       lc       &file     &@file          &,file       &@,file
+  directory  any      &/file    &@/file         &,/file      &@,/file
+             several  & f g h   &@ f g h        &, f g h     &@, f g h
+
+  Top        lc                 &.file          &;file       &@;file
+  level      any      file      &./file         &;/file      &@;/file
+             several  f g h     &. f g h        &; f g h     &@; f g h
+             .mk.in   file      $(abs)/file     $(src)/file  $(abs_src)/file
 
 Substitution syntax
 -------------------
@@ -182,6 +196,11 @@ empty string).
 &^             =>      $(top_srcdir)/sub/dir           or $(top_srcdir)
 &~             =>      $(abs_top_srcdir)/sub/dir       or $(abs_top_srcdir)
 
+In general:
+        ^       filenames in source tree rather than build tree
+        ~       filenames are absolute rather than relative
+        @       filenames do not contain subdir (useful with the above)
+
 &&             =>      &&              for convenience in shell runes
 \&             =>      &               general escaping mechanism