automatic regeneration for all of this template substitution, and for
config.status etc. is done for you.
+Summary of directory reference syntaxes
+---------------------------------------
+
+ 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
+ .mk.in file $(abs)/file $(src)/file $(abs_src)/file
+ several f g h & @~ f g h & @^ f g h & @~^ f g h
+
Substitution syntax
-------------------
&^ => $(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