From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Tue, 10 Dec 2019 01:21:43 +0000 (+0000)
Subject: README: v2: Draft - Introduce &. and friends
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?a=commitdiff_plain;h=24b7e76f14711aa1bc9aec57d9e5922054f32b37;p=subdirmk.git

README: v2: Draft - Introduce &. and friends

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

diff --git a/README b/README
index 6dd1a05..6ab45b9 100644
--- a/README
+++ b/README
@@ -218,27 +218,37 @@ empty string).
 	The assumption is that filenames are usually lowercase and
 	variables usually uppercase.  Otherwise, use another syntax:
 
+&/		=>	sub/dir/			or nothing
 &_		=>	sub_dir_			or TOP_
-&=_		=>	sub_dir				or TOP
+&.		=>	sub/dir				or .
+	(This implies that `&./' works roughly like `&/', although
+	it can produce a needless `./')
 
-&/		=>	sub/dir/			or nothing
-&=/		=>	sub/dir				or .
+&=		=>	sub_dir				or TOP
+^^^ rarely needed.  TBD, maybe one of
+	&._ &_. &\_ &% &$_
+	&<varnameprefix>  &[varnameprefix]
+	$(patsubst %_,&_,%)
 
 &^lc		=>	$(top_srcdir)/sub/dir/lc
 &^/		=>	$(top_srcdir)/sub/dir/
+&^.		=>	$(top_srcdir)/sub/dir
 
 &~lc		=>	$(top_srcdir)/lc
 &~/		=>	$(top_srcdir)/
+&~.		=>	$(top_srcdir)
 
 In general:
-    =	return subdir without delimiter (not allowed with `^' `~')
     ^   pathname of this subdirectory in source tree
     ~   pathname of top level of source tree
-    /	terminates the escape (needed if next is not lwsp or space)
+    /	terminates the path escape } needed if next is
+    _   terminates the var escape  } not lwsp or space)
+    .   terminates path escape giving dir name (excluding /)
+    =	terminates var escape giving only prefix part (rarely needed)
   lwsp  starts multi-word processing (see below)
 
 So pathname syntax is a subset of:
-    '&' [ '^' | '~' ] [ lc | '/' ]
+    '&' [ '^' | '~' ] [ lc | '/' | '.' | '=' ]
 
 &&		=>	&&		for convenience in shell runes
 &@		=>	&		general escaping mechanism