[PATCH 2/2] tests: fix tail test race causing false failure

[Pádraig Brady]

* tests/tail-2/retry.sh: The replacement of the "missing" directory
is not atomic, and therefore tail(1) can take a different path,
especially if there is a delay between the rmdir(2) and creat(2).
This is noticeable for example with `make coverage` because in
that case the coverage files written by rmdir(1) on exit,
induce a significant delay thus triggering the issue.
---
 tests/tail-2/retry.sh | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/tests/tail-2/retry.sh b/tests/tail-2/retry.sh
index 40d66d6..6901ca4 100755
--- a/tests/tail-2/retry.sh
+++ b/tests/tail-2/retry.sh
@@ -165,17 +165,18 @@ mkdir untailable || framework_failure_
 timeout 10 \
   tail $mode $fastpoll -F untailable >out 2>&1 & pid=$!
 # Wait for "cannot follow" error.
-retry_delay_ wait4lines_ .1 6 2 || { cat out; fail=1; }
+retry_delay_ wait4lines_ .1 6 2  || { cat out; fail=1; }
 { rmdir untailable; echo foo > untailable; }   || framework_failure_
 # Wait for the expected output.
-retry_delay_ wait4lines_ .1 6 4 || { cat out; fail=1; }
+retry_delay_ wait4lines_ .1 6 4  || { cat out; fail=1; }
 cleanup_
-[ "$(countlines_)" = 4 ]                       || { fail=1; cat out; }
-grep -F 'cannot follow' out                    || { fail=1; cat out; }
-grep -F 'has become accessible' out            || { fail=1; cat out; }
-grep -F 'giving up'             out            && { fail=1; cat out; }
-grep -F 'foo' out                              || { fail=1; cat out; }
-rm -fd untailable out                          || framework_failure_
+[ "$(countlines_)" = 4 ]         || { fail=1; cat out; }
+grep -F 'cannot follow' out      || { fail=1; cat out; }
+grep -F 'become accessible' out  ||                      # usual case
+grep -F 'has appeared' out       || { fail=1; cat out; } # with slow rmdir
+grep -F 'giving up' out          && { fail=1; cat out; }
+grep -F 'foo' out                || { fail=1; cat out; }
+rm -fd untailable out            || framework_failure_
 fi
 
 done
-- 
2.5.5