Change definitions of $1,$2,$3 to match djb's redo.

If you use "redo --old-args", it will switch back to the old
(apenwarr-style) arguments for now, to give you time to update your .do
scripts.  This option will go away eventually.

Note: minimal/do doesn't understand the --old-args option.  If you're using
minimal/do in your project, keep using the old one until you update your use
of $1/$2, and then update to the new one.

apenwarr-style default.o.do:
   $1      foo
   $2      .o
   $3      whatever.tmp

djb-style default.o.do:
   $1      foo.o
   $2      foo
   $3      whatever.tmp

apenwarr-style foo.o.do:
   $1      foo.o
   $2      ""
   $3      whatever.tmp

djb-style foo.o.do:
   $1      foo.o
   $2      foo.o  (I think?)
   $3      whatever.tmp

Documentation/default.1.do

@@ -1,2 +1,2 @@
-redo-ifchange md-to-man $1.md.tmp
+redo-ifchange md-to-man $2.md.tmp
 . ./md-to-man $1 $2 $3

Documentation/default.md.tmp.do

@@ -1,3 +1,3 @@
-redo-ifchange ../version/vars $1.md
+redo-ifchange ../version/vars $2.md
 . ../version/vars
-sed -e "s/%VERSION%/$TAG/" -e "s/%DATE%/$DATE/" $1.md
+sed -e "s/%VERSION%/$TAG/" -e "s/%DATE%/$DATE/" $2.md

Documentation/md-to-man.do

@@ -1,8 +1,8 @@
 redo-ifchange md2man.py
 if ./md2man.py </dev/null >/dev/null; then
-	echo './md2man.py $1.md.tmp'
+	echo './md2man.py $2.md.tmp'
 else
 	echo "Warning: md2man.py missing modules; can't generate manpages." >&2
 	echo "Warning: try this: sudo easy_install markdown BeautifulSoup" >&2
-	echo 'echo Skipping: $1.1 >&2'
+	echo 'echo Skipping: $2.1 >&2'
 fi

Documentation/redo-ifchange.md

@@ -48,10 +48,10 @@ of .h files it depends on. You can pass this information
 along to redo-ifchange, so if any of those headers are
 changed or deleted, your .c file will be rebuilt:
 
-        redo-ifchange $1.c
-        gcc -o $3 -c $1.c \
-            -MMD -MF $1.deps
-        read DEPS <$1.deps
+        redo-ifchange $2.c
+        gcc -o $3 -c $2.c \
+            -MMD -MF $2.deps
+        read DEPS <$2.deps
         redo-ifchange ${DEPS#*:}
 
 This is much less confusing than the equivalent

Documentation/redo.md

@@ -104,6 +104,14 @@ dependencies.
     output message.  This makes it easier to figure out
     which sub-instance of redo is doing what.
 
+--old-args
+:   old versions of redo provided different definitions of
+    the $1 and $2 parameters to .do scripts.  The new
+    version is compatible with djb's original
+    specification.  This option goes back to the old
+    definitions so you can use .do scripts you haven't yet
+    converted to the new style.
+
 
 # DISCUSSION
 
@@ -156,8 +164,8 @@ redo does not have this problem.)
 
 The three arguments passed to the .do script are:
 
-- $1: the basename of the target (eg. mytarget.a.b)
-- $2: the extension of the target, if any (eg. .c.d)
+- $1: the target name (eg. mytarget.a.b)
+- $2: the basename of the target, minus its extension (eg. mytarget)
 - $3: a temporary filename that the .do script should write
   its output to.
   
@@ -165,7 +173,7 @@ Instead of using $3, the .do script may also write the
 produced data to stdout.
 
 If the .do file is in the same directory as the target, $1
-and $3 are guaranteed to be simple filenames (with no path
+is guaranteed to be a simple filename (with no path
 component).  If the .do file is in a parent directory of
 the target, $1 and $3 will be relative paths (ie. will
 contain slashes).