grep: with no args, search "." only if command-line -r

* NEWS: Document this.
* doc/grep.texi (Environment Variables, grep Programs): Likewise.
* src/main.c (usage): Likewise.
(main): Implement this.
(prepend_default_options): Return a count of prepended options.
* tests/r-dot: Test the above.

4 files changed, 38 insertions, 13 deletions

diff --git a/NEWS b/NEWS
index 0fd60390..b36cab7d 100644
--- a/NEWS
+++ b/NEWS
@@ -35,8 +35,10 @@ GNU grep NEWS                                    -*- outline -*-
 
 ** New features
 
-  If no file operand is given, grep -r now searches the working directory.
-  Formerly it ignored the -r and searched standard input nonrecursively.
+  If no file operand is given, and a command-line -r or equivalent
+  option is given, grep now searches the working directory.  Formerly
+  grep ignored the -r and searched standard input nonrecursively.
+  An -r found in GREP_OPTIONS does not have this new effect.
 
   grep now supports color highlighting of matches on MS-Windows.
 
diff --git a/doc/grep.texi b/doc/grep.texi
index 5d779c11..78efb189 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -801,6 +801,13 @@ whitespace.
 A backslash escapes the next character, so it can be used to
 specify an option containing whitespace or a backslash.
 
+The @code{GREP_OPTIONS} value does not affect whether @command{grep}
+without file operands searches standard input or the working
+directory; that is affected only by command-line options.  For
+example, the command @samp{grep PAT} searches standard input and the
+command @samp{grep -r PAT} searches the working directory, regardless
+of whether @code{GREP_OPTIONS} contains @option{-r}.
+
 @item GREP_COLOR
 @vindex GREP_COLOR @r{environment variable}
 @cindex highlight markers
@@ -1014,9 +1021,9 @@ instead of strict equality with@ 2.
 for lines containing a match to the given pattern.
 By default, @command{grep} prints the matching lines.
 A file named @file{-} stands for standard input.
-If no input is specified, a recursive @command{grep}
-searches the working directory @file{.}, and a
-nonrecursive @command{grep} searches standard input.
+If no input is specified, @command{grep} searches the working
+directory @file{.} if given a command-line option specifying
+recursion; otherwise, @command{grep} searches standard input.
 There are four major variants of @command{grep},
 controlled by the following options.
 
diff --git a/src/main.c b/src/main.c
index a738050c..51135ad0 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1522,8 +1522,8 @@ Context control:\n\
 \n"));
       fputs (_(after_options), stdout);
       printf (_("\
-When FILE is -, read standard input.  With no FILE, read '.' if recursive,\n\
-standard input if not.  If fewer than two FILEs are given, assume -h.\n\
+When FILE is -, read standard input.  With no FILE, read . if a command-line\n\
+-r is given, - otherwise.  If fewer than two FILEs are given, assume -h.\n\
 Exit status is 0 if any line is selected, 1 otherwise;\n\
 if any error occurs and -q is not given, the exit status is 2.\n"));
       printf (_("\nReport bugs to: %s\n"), PACKAGE_BUGREPORT);
@@ -1646,8 +1646,8 @@ prepend_args (char const *options, char *buf, char **argv)
 
 /* Prepend the whitespace-separated options in OPTIONS to the argument
    vector of a main program with argument count *PARGC and argument
-   vector *PARGV.  */
-static void
+   vector *PARGV.  Return the number of options prepended.  */
+static int
 prepend_default_options (char const *options, int *pargc, char ***pargv)
 {
   if (options && *options)
@@ -1663,7 +1663,10 @@ prepend_default_options (char const *options, int *pargc, char ***pargv)
       pp += prepend_args (options, buf, pp);
       while ((*pp++ = *argv++))
         continue;
+      return prepended;
     }
+
+  return 0;
 }
 
 /* Get the next non-digit option from ARGC and ARGV.
@@ -1807,7 +1810,8 @@ main (int argc, char **argv)
   char *keys;
   size_t keycc, oldcc, keyalloc;
   int with_filenames;
-  int opt, cc, status;
+  int opt, cc, status, prepended;
+  int prev_optind, last_recursive;
   int default_context;
   FILE *fp;
 
@@ -1843,10 +1847,12 @@ main (int argc, char **argv)
   exit_failure = EXIT_TROUBLE;
   atexit (close_stdout);
 
-  prepend_default_options (getenv ("GREP_OPTIONS"), &argc, &argv);
+  last_recursive = 0;
+  prepended = prepend_default_options (getenv ("GREP_OPTIONS"), &argc, &argv);
   setmatcher (NULL);
 
-  while ((opt = get_nondigit_option (argc, argv, &default_context)) != -1)
+  while (prev_optind = optind,
+         (opt = get_nondigit_option (argc, argv, &default_context)) != -1)
     switch (opt)
       {
       case 'A':
@@ -1936,6 +1942,8 @@ main (int argc, char **argv)
       case 'd':
         directories = XARGMATCH ("--directories", optarg,
                                  directories_args, directories_types);
+        if (directories == RECURSE_DIRECTORIES)
+          last_recursive = prev_optind;
         break;
 
       case 'e':
@@ -2024,6 +2032,7 @@ main (int argc, char **argv)
       case 'R':
       case 'r':
         directories = RECURSE_DIRECTORIES;
+        last_recursive = prev_optind;
         break;
 
       case 's':
@@ -2250,7 +2259,7 @@ main (int argc, char **argv)
         }
       while (++optind < argc);
     }
-  else if (directories == RECURSE_DIRECTORIES)
+  else if (directories == RECURSE_DIRECTORIES && prepended < last_recursive)
     {
       status = 1;
       if (stat (".", &stats_base.stat) == 0)
diff --git a/tests/r-dot b/tests/r-dot
index 73e593cf..a1d5c0a5 100755
--- a/tests/r-dot
+++ b/tests/r-dot
@@ -11,4 +11,11 @@ echo a:aaa > exp || framework_failure_
 (cd dir && grep -r aaa) > out || fail=1
 compare exp out || fail=1
 
+(cd dir && grep -r aaa < a) > out || fail=1
+compare exp out || fail=1
+
+echo aaa > exp || framework_failure_
+(cd dir && GREP_OPTIONS=-r grep aaa < a) > out || fail=1
+compare exp out || fail=1
+
 Exit $fail