Simplify autodependency examples.

Turns out we don't need sed to process the output of gcc -MD.  We can just
do this:

	read DEPS <filename.deps

The 'read' command in sh actually handles backslashes correctly, so we don't
have to sed them out after all.  And then a simple ${DEPS#*:} removes the
"target:" prefix from the dependency line, and we're done!

Documentation/redo-ifchange.md

@@ -48,11 +48,11 @@ 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$2
-        gcc -o $3 -c $1$2 \
-            -MMD -MF $1.deps -MT DELETE_ME
-        redo-ifchange $(sed -e 's,^DELETE_ME:,,' \
-                            -e 's,\\,,' $1.deps)
+        redo-ifchange $1.c
+        gcc -o $3 -c $1.c \
+            -MMD -MF $1.deps
+        read DEPS <$1.deps
+        redo-ifchange ${DEPS#*:}
 
 This is much less confusing than the equivalent
 autodependency mechanism in `make`(1), because make

README.md

@@ -75,10 +75,9 @@ The easiest way to show it is with an example.
 Create a file called default.o.do:
 
 	redo-ifchange $1.c
-	gcc -MD -MF $3.deps.tmp -c -o $3 $1.c
-	DEPS=$(sed -e "s/^$3://" -e 's/\\//g' <$3.deps.tmp)
-	rm -f $3.deps.tmp
-	redo-ifchange $DEPS
+	gcc -MD -MF $1.d -c -o $3 $1.c
+	read DEPS <$1.d
+	redo-ifchange ${DEPS#*:}
 
 Create a file called myprog.do:
 

t/example/CC.do

@@ -3,9 +3,9 @@ redo-ifchange config.sh
 exec >$3
 cat <<-EOF
 	redo-ifchange \$1.c
-	gcc $CFLAGS -MD -MF \$3.deps.tmp -o \$3 -c \$1.c
-	DEPS=\$(sed -e "s/^\$3://" -e 's/\\\\//g' <\$3.deps.tmp)
-	rm -f \$3.deps.tmp
-	redo-ifchange \$DEPS
+	gcc $CFLAGS -MD -MF \$3.deps -o \$3 -c \$1.c
+	read DEPS <\$3.deps
+	rm -f \$3.deps
+	redo-ifchange \${DEPS#*:}
 EOF
 chmod +x $3