[Bug-ed] ed(1) doesn't support "^" address

[Tim Chase]

The original Unix™ ed(1) supported a "^" address which was a synonym
for "-".  Supporting documentation can be seen at the top of page 4 in
the right-hand column:

http://webhome.csc.uvic.ca/~mcheng/360/xv6/unixv6/ed.pdf 

"""
 Try typing "ˆ" — it's equivalent to ".-1p"
"""

as well as item #10 here:

http://roguelife.org/~fujita/COOKIES/HISTORY/V6/ed.1.html

("To maintain compatibility with earlier version of the editor, the
character `^' in addresses is entirely equivalent to `-'.")

Based on my reading of the above two documents, I believe the diff
below should provide the functionality/backwards-compatibility.  I
don't know how the testing scheme works so you might want to make up
a test for this.

-Tim

(in case you need some sort of contributor statement, as the author
of the diff, I hearby release this diff into the public domain, so do
what you want with it)

diff --git a/main_loop.c b/main_loop.c
index 2081b38..2d058d1 100644
--- a/main_loop.c
+++ b/main_loop.c
@@ -213,14 +213,15 @@ static int next_addr( const char ** const
ibufpp, int * const addr_cnt ) case '+':
       case '\t':
       case ' ':
+      case '^':
       case '-': *ibufpp = skip_blanks( ++*ibufpp );
                 if( isdigit( (unsigned char)**ibufpp ) )
                   {
                   if( !parse_int( &n, *ibufpp, ibufpp ) ) return -2;
-                  addr += ( ( ch == '-' ) ? -n : n );
+                  addr += ( ( ch == '-' || ch == '^' ) ? -n : n );
                   }
                 else if( ch == '+' ) ++addr;
-                else if( ch == '-' ) --addr;
+                else if( ch == '-' || ch == '^' ) --addr;
                 break;
       case '.':
       case '$': if( !first ) { invalid_address(); return -2; };




.