tests/ls/stat-free-colors.sh broken with glibc-2.22

[Bernhard Voelker]

The above test is broken with latest glibc, seen first on openSUSE:Factory:

  + strace -o log -e stat,lstat,stat64,lstat64,newfstatat ls --color=always .
  color-without-stat
  dangle
  log
  log-help
  ++ wc -l
  + n_lines=3
  ++ expr 3 - 1
  + n_stat=2
  + case $n_stat in
  + fail=1
  + head -n30 log log-help
  ==> log <==
  stat(".", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
  stat(".", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
  +++ exited with 0 +++

  ==> log-help <==
  +++ exited with 0 +++
  + Exit 1

The effect is that for every directory-type argument, ls(1) does an extra
call to stat().  I could trace it down to main()->print_dirs() which in
turn calls glibc's opendir().

This is since glibc-2.22 ... and specifically this commit:
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=glibc-2.21-360-g46f894d

As can be seen in the following diff of strace outputs, opendir(".") has
been changed from a simple openat() to the sequence of stat()+open():

  ...
   stat(".", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
  -openat(AT_FDCWD, ".", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
  +stat(".", {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
  +open(".", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
  +fstat(3, {st_mode=S_IFDIR|0700, st_size=4096, ...}) = 0
   getdents(3, /* 5 entries */, 32768)     = 152
   getdents(3, /* 0 entries */, 32768)     = 0
   close(3)                                = 0
  ...

As we can't predict the number of stat() calls as before,
what shall we do to fix the test?

Have a nice day,
Berny