pinky: disable location canonicalization by default

Behave like who(1) in requiring --lookup to enable this
often slow feature.  pinky(1) is supposed to be lightweight after all.

* doc/coreutils.texi (who invocation): Adjust the description to no
longer reference dialup, and be more general about the still significant
delays.
(pinky invocation): Reference the same --lookup description.
* src/pinky.c (main): Accept --lookup to enable DNS lookups.
* NEWS: Mention the change in behavior.
Fixes https://bugs.debian.org/628815

NEWS

@@ -65,6 +65,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   numfmt will accept lowercase 'k' to indicate Kilo or Kibi units on input,
   and uses lowercase 'k' when outputting such units in '--to=si' mode.
 
+  pinky no longer tries to canonicalize the user's login location by default,
+  rather requiring the new --lookup option to enable this often slow feature.
+
   wc no longer ignores encoding errors when counting words.
   Instead, it treats them as non white space.
 

doc/coreutils.texi

@@ -16203,11 +16203,13 @@ Print a line of column headings.
 List only the entries that correspond to processes via which the
 system is waiting for a user to login.  The user name is always @samp{LOGIN}.
 
+@macro lookupOption
 @item --lookup
 @opindex --lookup
-Attempt to canonicalize hostnames found in utmp through a DNS lookup.  This
-is not the default because it can cause significant delays on systems with
-automatic dial-up internet access.
+Attempt to canonicalize hostnames found in utmp through a DNS lookup.
+This is not the default because of potential delays.
+@end macro
+@lookupOption
 
 @item -m
 @opindex -m
@@ -16335,6 +16337,8 @@ format.
 Omit the user's full name, remote host, and idle time when printing in
 short format.
 
+@lookupOption
+
 @end table
 
 @exitstatus

src/pinky.c

@@ -61,6 +61,9 @@ static bool include_home_and_shell = true;
 /* if true, use the "short" output format. */
 static bool do_short_format = true;
 
+/* If true, attempt to canonicalize hostnames via a DNS lookup. */
+static bool do_lookup;
+
 /* if true, display the ut_host field. */
 #if HAVE_STRUCT_XTMP_UT_HOST
 static bool include_where = true;
@@ -71,8 +74,15 @@ static bool include_where = true;
 static char const *time_format;
 static int time_format_width;
 
+/* for long options with no corresponding short option, use enum */
+enum
+{
+  LOOKUP_OPTION = CHAR_MAX + 1
+};
+
 static struct option const longopts[] =
 {
+  {"lookup", no_argument, nullptr, LOOKUP_OPTION},
   {GETOPT_HELP_OPTION_DECL},
   {GETOPT_VERSION_OPTION_DECL},
   {nullptr, 0, nullptr, 0}
@@ -279,7 +289,7 @@ print_entry (struct gl_utmp const *utmp_ent)
       if (display)
         *display++ = '\0';
 
-      if (*ut_host)
+      if (*ut_host && do_lookup)
         /* See if we can canonicalize it.  */
         host = canon_host (ut_host);
       if ( ! host)
@@ -499,6 +509,9 @@ usage (int status)
   -i              omit the user's full name and remote host in short format\n\
   -q              omit the user's full name, remote host and idle time\n\
                   in short format\n\
+"), stdout);
+      fputs (_("\
+      --lookup    attempt to canonicalize hostnames via DNS\n\
 "), stdout);
       fputs (HELP_OPTION_DESCRIPTION, stdout);
       fputs (VERSION_OPTION_DESCRIPTION, stdout);
@@ -574,6 +587,10 @@ main (int argc, char **argv)
           include_home_and_shell = false;
           break;
 
+        case LOOKUP_OPTION:
+          do_lookup = true;
+          break;
+
         case_GETOPT_HELP_CHAR;
 
         case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);