ls --color: don't emit a final no-op escape sequence

* src/ls.c (main): With --color, avoid emitting the final color-
resetting escape sequence when it would be a no-op.
* tests/ls/color-clear-to-eol: Adjust expected output accordingly.
* tests/ls/color-dtype-dir: Likewise.
* tests/ls/multihardlink: Likewise.
* tests/ls/stat-free-symlinks: Likewise.
* tests/misc/ls-misc: Likewise.
* NEWS (Changes in behavior): Mention it.
C de-Avillez rebased and adapted four of the new sl-dangle*
tests in tests/misc/ls-misc.
Reported by Jim Avera in
http://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/494663

7 files changed, 28 insertions, 22 deletions

diff --git a/NEWS b/NEWS
index f4c7f97d5..aa37d69e0 100644
--- a/NEWS
+++ b/NEWS
@@ -14,6 +14,11 @@ GNU coreutils NEWS                                    -*- outline -*-
   using the --with-tty-group[=NAME] option, who also compares the group
   of the TTY device with NAME (or "tty" if no group name is specified).
 
+** Changes in behavior
+
+  ls --color no longer emits the final 3-byte color-resetting escape
+  sequence when it would be a no-op.
+
 
 * Noteworthy changes in release 8.4 (2010-01-13) [stable]
 
diff --git a/src/ls.c b/src/ls.c
index 9ef7eba21..680679a9a 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -1442,7 +1442,15 @@ main (int argc, char **argv)
       int j;
 
       if (used_color)
-        restore_default_color ();
+        {
+          /* Skip the restore when it would be a no-op, i.e.,
+             when left is "\033[" and right is "m".  */
+          if (!(color_indicator[C_LEFT].len == 2
+                && memcmp (color_indicator[C_LEFT].string, "\033[", 2) == 0
+                && color_indicator[C_RIGHT].len == 1
+                && color_indicator[C_RIGHT].string[0] == 'm'))
+            restore_default_color ();
+        }
       fflush (stdout);
 
       /* Restore the default signal handling.  */
diff --git a/tests/ls/color-clear-to-eol b/tests/ls/color-clear-to-eol
index 96944cb6d..1be68cab6 100755
--- a/tests/ls/color-clear-to-eol
+++ b/tests/ls/color-clear-to-eol
@@ -29,7 +29,7 @@ touch $long_name || framework_failure
 e='\33'
 color_code='0;31;42'
 c_pre="$e[0m$e[${color_code}m"
-c_post="$e[0m$e[K\n$e[m"
+c_post="$e[0m$e[K\n"
 printf "$c_pre$long_name$c_post\n" > exp || framework_failure
 
 env TERM=xterm COLUMNS=80 LS_COLORS="*.foo=$color_code" TIME_STYLE=+T \
diff --git a/tests/ls/color-dtype-dir b/tests/ls/color-dtype-dir
index 6532d8415..29b872c21 100755
--- a/tests/ls/color-dtype-dir
+++ b/tests/ls/color-dtype-dir
@@ -36,7 +36,6 @@ chmod o+t sticky || framework_failure
 
 ls --color=always > out || fail=1
 cat -A out > o1 || fail=1
-echo >> o1 || fail=1
 mv o1 out || fail=1
 
 cat <<\EOF > exp || fail=1
@@ -44,7 +43,6 @@ cat <<\EOF > exp || fail=1
 ^[[34;42mother-writable^[[0m$
 out$
 ^[[37;44msticky^[[0m$
-^[[m
 EOF
 
 compare out exp || fail=1
@@ -56,7 +54,6 @@ rm exp
 
 LS_COLORS="ow=:" ls --color=always > out || fail=1
 cat -A out > o1 || fail=1
-echo >> o1 || fail=1
 mv o1 out || fail=1
 
 cat <<\EOF > exp || fail=1
@@ -64,7 +61,6 @@ cat <<\EOF > exp || fail=1
 ^[[01;34mother-writable^[[0m$
 out$
 ^[[37;44msticky^[[0m$
-^[[m
 EOF
 
 compare out exp || fail=1
diff --git a/tests/ls/multihardlink b/tests/ls/multihardlink
index 60bb39948..20a94c807 100755
--- a/tests/ls/multihardlink
+++ b/tests/ls/multihardlink
@@ -30,7 +30,6 @@ code_mh='44;37'
 code_ex='01;32'
 code_png='01;35'
 c0=$(printf '\033[0m')
-c_end=$(printf '\033[m')
 c_mh=$(printf '\033[%sm' $code_mh)
 c_ex=$(printf '\033[%sm' $code_ex)
 c_png=$(printf '\033[%sm' $code_png)
@@ -44,7 +43,7 @@ compare out out_ok || fail=1
 LS_COLORS="mh=$code_mh" ls -U1 --color=always file1 file2 > out || fail=1
 printf "$c0${c_mh}file1$c0
 ${c_mh}file2$c0
-$c_end" > out_ok || framework_failure
+" > out_ok || framework_failure
 compare out out_ok || fail=1
 
 # hard links and png (hard link coloring takes precedence)
@@ -53,7 +52,7 @@ LS_COLORS="mh=$code_mh:*.png=$code_png" ls -U1 --color=always file1 file2.png \
   > out || fail=1
 printf "$c0${c_mh}file1$c0
 ${c_mh}file2.png$c0
-$c_end" > out_ok || framework_failure
+" > out_ok || framework_failure
 compare out out_ok || fail=1
 
 # hard links and exe (exe coloring takes precedence)
@@ -63,7 +62,7 @@ LS_COLORS="mh=$code_mh:*.png=$code_png:ex=$code_ex" \
 chmod a-x file2.png || framework_failure
 printf "$c0${c_ex}file1$c0
 ${c_ex}file2.png$c0
-$c_end" > out_ok || framework_failure
+" > out_ok || framework_failure
 compare out out_ok || fail=1
 
 # hard links and png (hard link coloring disabled => png coloring enabled)
@@ -71,7 +70,7 @@ LS_COLORS="mh=00:*.png=$code_png" ls -U1 --color=always file1 file2.png > out \
   || fail=1
 printf "file1
 $c0${c_png}file2.png$c0
-$c_end" > out_ok || framework_failure
+" > out_ok || framework_failure
 compare out out_ok || fail=1
 
 # hard links and png (hard link coloring not enabled explicitly => png coloring)
@@ -79,7 +78,7 @@ LS_COLORS="*.png=$code_png" ls -U1 --color=always file1 file2.png > out \
   || fail=1
 printf "file1
 $c0${c_png}file2.png$c0
-$c_end" > out_ok || framework_failure
+" > out_ok || framework_failure
 compare out out_ok || fail=1
 
 Exit $fail
diff --git a/tests/ls/stat-free-symlinks b/tests/ls/stat-free-symlinks
index f6cdb9131..6843b97fd 100755
--- a/tests/ls/stat-free-symlinks
+++ b/tests/ls/stat-free-symlinks
@@ -46,7 +46,6 @@ grep '^stat("x"' err && fail=1
 {
   printf '\033[0m\033[01;35mlink-to-x\033[0m@\n'
   printf '\033[01;32mx\033[0m*\n'
-  printf '\033[m'
 } > exp || fail=1
 
 compare out exp || fail=1
diff --git a/tests/misc/ls-misc b/tests/misc/ls-misc
index 27de57c79..e663a5fc8 100755
--- a/tests/misc/ls-misc
+++ b/tests/misc/ls-misc
@@ -156,10 +156,10 @@ my @Tests =
 
      # Test for a bug that was fixed in coreutils-4.5.4.
      ['sl-F-color', '-F --color=always d',
-                                 {OUT => "$e\e[01;36md$e\@\n\e[m"},
+                                 {OUT => "$e\e[01;36md$e\@\n"},
                                   $slink_d, $unlink_d],
      ['sl-dF-color', '-dF --color=always d',
-                                 {OUT => "$e\e[01;36md$e\@\n\e[m"},
+                                 {OUT => "$e\e[01;36md$e\@\n"},
                                   $slink_d, $unlink_d],
 
      # A listing with no output should have no color sequences at all.
@@ -169,12 +169,12 @@ my @Tests =
 
      # Test for a bug fixed after coreutils-6.9.
      ['sl-target', '--color=always d',
-      {OUT => "$e\e[01;34mX$e\n\e[m"}, $target, $target2],
+      {OUT => "$e\e[01;34mX$e\n"}, $target, $target2],
 
      # Test for another bug fixed after coreutils-6.9.
      # This one bites only for a system/file system with d_type support.
      ['sl-dangle', '--color=always d',
-      {OUT => "$e\e[40;31;01mX$e\n\e[m"},
+      {OUT => "$e\e[40;31;01mX$e\n"},
       {PRE => sub {
                 mkdir 'd',0755 or die "d: $!\n";
                 symlink 'non-existent', 'd/X' or die "d/X: $!\n";
@@ -197,7 +197,7 @@ my @Tests =
      ],
      ['sl-dangle3', '-o --color=always l',
       {OUT_SUBST => 's/.*[0-9][0-9]:[0-9][0-9] //'},
-      {OUT => "$e\e[40ml$e -> \e[34mnowhere$e\n\e[m"},
+      {OUT => "$e\e[40ml$e -> \e[34mnowhere$e\n"},
       {PRE => sub {symlink 'nowhere', 'l' or die "l: $!\n";
                    push_ls_colors('ln=target:or=40:mi=34:')
        }},
@@ -206,7 +206,7 @@ my @Tests =
      ],
      ['sl-dangle4', '-o --color=always l',
       {OUT_SUBST => 's/.*[0-9][0-9]:[0-9][0-9] //'},
-      {OUT => "$e\e[36ml$e -> \e[35mnowhere$e\n\e[m"},
+      {OUT => "$e\e[36ml$e -> \e[35mnowhere$e\n"},
       {PRE => sub {symlink 'nowhere', 'l' or die "l: $!\n";
                    push_ls_colors('ln=34:mi=35:or=36:')
        }},
@@ -215,7 +215,7 @@ my @Tests =
      ],
      ['sl-dangle5', '-o --color=always l',
       {OUT_SUBST => 's/.*[0-9][0-9]:[0-9][0-9] //'},
-      {OUT => "$e\e[34ml$e -> \e[35mnowhere$e\n\e[m"},
+      {OUT => "$e\e[34ml$e -> \e[35mnowhere$e\n"},
       {PRE => sub {symlink 'nowhere', 'l' or die "l: $!\n";
                    push_ls_colors('ln=34:mi=35:')
        }},
@@ -227,7 +227,7 @@ my @Tests =
      # To demonstrate it, the file in question (with executable bit set)
      # must not be a command line argument.
      ['color-exe1', '--color=always j',
-                                 {OUT => "$e\e[01;32md$e\n\e[m"},
+                                 {OUT => "$e\e[01;32md$e\n"},
                                   $exe_in_subdir, $remove_j],
 
      # From Stéphane Chazelas.
@@ -245,7 +245,6 @@ my @Tests =
             . "\e[30;43msetgid$e\n"
             . "\e[37;41msetuid$e\n"
             . "\e[37;44msticky$e\n"
-            . "\e[m"
          },
 
         {POST => sub {