From 7bee5eee0a719cd6ccd1e7ac2e36bf1e10ac123e Mon Sep 17 00:00:00 2001
From: Paul Eggert <address@hidden>
Date: Sat, 10 May 2014 01:21:15 -0700
Subject: [PATCH 1/2] grep: -A 0, -B 0, -C 0 now output a separator

Problem reported by Dan Jacobson in: http://bugs.gnu.org/17380
* NEWS:
* doc/grep.texi (Context Line Control): Document this.
* src/grep.c (prtext): Output a separator even if context is zero.
(main): Default context is now -1, not 0.
---
 NEWS          |  4 ++++
 doc/grep.texi | 18 ++++++++----------
 src/grep.c    |  5 +++--
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/NEWS b/NEWS
index 3a20096..685ce9b 100644
--- a/NEWS
+++ b/NEWS
@@ -11,6 +11,10 @@ GNU grep NEWS                                    -*- outline -*-
   grep no longer mishandles an empty pattern at the end of a pattern list.
   [bug introduced in grep-2.5]
 
+  grep -C NUM now outputs separators consistently even when NUM is zero,
+  and similarly for grep -A NUM and grep -B NUM.
+  [bug present since "the beginning"]
+
   grep -f no longer mishandles patterns containing NUL bytes.
   [bug introduced in grep-2.11]
 
diff --git a/doc/grep.texi b/doc/grep.texi
index 59d0d3c..feee0d8 100644
--- a/doc/grep.texi
+++ b/doc/grep.texi
@@ -532,14 +532,13 @@ Print @var{num} lines of leading and trailing output context.
 @opindex --group-separator
 @cindex group separator
 When @option{-A}, @option{-B} or @option{-C} are in use,
-print @var{string} instead of @option{--} around disjoint groups
-of lines.
+print @var{string} instead of @option{--} between groups of lines.
 
 @item --no-group-separator
 @opindex --group-separator
 @cindex group separator
 When @option{-A}, @option{-B} or @option{-C} are in use,
-print disjoint groups of lines adjacent to each other.
+do not print a separator between groups of lines.
 
 @end table
 
@@ -555,26 +554,25 @@ between prefix fields and actual line content.
 Context (i.e., non-matching) lines use @samp{-} instead.
 
 @item
-When no context is specified,
+When context is not specified,
 matching lines are simply output one right after another.
 
 @item
-When nonzero context is specified,
+When context is specified,
 lines that are adjacent in the input form a group
 and are output one right after another, while
-a separator appears by default between disjoint groups on a line
-of its own and without any prefix.
+by default a separator appears between non-adjacent groups.
 
 @item
 The default separator
-is @samp{--}, however whether to include it and its appearance
+is a @samp{--} line; its presence and appearance
 can be changed with the options above.
 
 @item
 Each group may contain
 several matching lines when they are close enough to each other
-that two otherwise adjacent but divided groups connect
-and can just merge into a single contiguous one.
+that two adjacent groups connect and can merge into a single
+contiguous one.
 @end itemize
 
 @node File and Directory Selection
diff --git a/src/grep.c b/src/grep.c
index 1e3fc28..ec955d8 100644
--- a/src/grep.c
+++ b/src/grep.c
@@ -1002,7 +1002,8 @@ prtext (char const *beg, char const *lim)
 
       /* Print the group separator unless the output is adjacent to
          the previous output in the file.  */
-      if ((out_before || out_after) && used && p != lastout && group_separator)
+      if ((0 <= out_before || 0 <= out_after) && used
+          && p != lastout && group_separator)
         {
           pr_sgr_start_if (sep_color);
           fputs (group_separator, stdout);
@@ -1961,7 +1962,7 @@ main (int argc, char **argv)
   /* The value -1 means to use DEFAULT_CONTEXT. */
   out_after = out_before = -1;
   /* Default before/after context: changed by -C/-NUM options */
-  default_context = 0;
+  default_context = -1;
   /* Changed by -o option */
   only_matching = 0;
 
-- 
1.9.0