head: fix --lines=-0 outputting nothing if no newline at EOF

* src/head.c (elide_tail_lines_pipe): Just output all input in
this case to avoid the issue and also avoid redundant '\n' processing.
(elide_tail_lines_seekable): Likewise.
* tests/misc/head-elide-tail.pl: Add tests for no '\n' at EOF.
* NEWS: Mention the fix.
Fixes http://bugs.gnu.org/16329

1 files changed, 5 insertions, 2 deletions

diff --git a/tests/misc/head-elide-tail.pl b/tests/misc/head-elide-tail.pl
index 758e1c9d0..3c178d695 100755
--- a/tests/misc/head-elide-tail.pl
+++ b/tests/misc/head-elide-tail.pl
@@ -52,6 +52,8 @@ my @Tests =
    ['elide-l2', "--lines=-1", {IN=>"a"}, {OUT=>''}],
    ['elide-l3', "--lines=-1", {IN=>"a\nb"}, {OUT=>"a\n"}],
    ['elide-l4', "--lines=-1", {IN=>"a\nb\n"}, {OUT=>"a\n"}],
+   ['elide-l5', "--lines=-0", {IN=>"a\nb\n"}, {OUT=>"a\nb\n"}],
+   ['elide-l6', "--lines=-0", {IN=>"a\nb"}, {OUT=>"a\nb"}],
   );
 
 if ($ENV{RUN_EXPENSIVE_TESTS})
@@ -80,9 +82,10 @@ if ($ENV{RUN_EXPENSIVE_TESTS})
       }
 
     $s =~ s/(.)/$1\n/g;
-    for my $file_size (0..20)
+    $s .= 'u'; # test without trailing '\n'
+    for my $file_size (0..21)
       {
-        for my $n_elide (0..20)
+        for my $n_elide (0..21)
           {
             my $input = substr $s, 0, 2 * $file_size;
             my $out_len = $n_elide < $file_size ? $file_size - $n_elide : 0;