Merge branch 'sg/test-x'

Running test scripts under -x option of the shell is often not a
useful way to debug them, because the error messages from the
commands tests try to capture and inspect are contaminated by the
tracing output by the shell.  An earlier work done to make it more
pleasant to run tests under -x with recent versions of bash is
extended to cover posix shells that do not support BASH_XTRACEFD.

* sg/test-x:
  travis-ci: run tests with '-x' tracing
  t/README: add a note about don't saving stderr of compound commands
  t1510-repo-setup: mark as untraceable with '-x'
  t9903-bash-prompt: don't check the stderr of __git_ps1()
  t5570-git-daemon: don't check the stderr of a subshell
  t5526: use $TRASH_DIRECTORY to specify the path of GIT_TRACE log file
  t5500-fetch-pack: don't check the stderr of a subshell
  t3030-merge-recursive: don't check the stderr of a subshell
  t1507-rev-parse-upstream: don't check the stderr of a shell function
  t: add means to disable '-x' tracing for individual test scripts
  t: prevent '-x' tracing from interfering with test helpers' stderr

1 files changed, 20 insertions, 3 deletions

diff --git a/t/README b/t/README
index 1a1361a..24ddebf 100644
--- a/t/README
+++ b/t/README
@@ -84,9 +84,10 @@ appropriately before running "make".
 
 -x::
 	Turn on shell tracing (i.e., `set -x`) during the tests
-	themselves. Implies `--verbose`. Note that in non-bash shells,
-	this can cause failures in some tests which redirect and test
-	the output of shell functions. Use with caution.
+	themselves. Implies `--verbose`.
+	Ignored in test scripts that set the variable 'test_untraceable'
+	to a non-empty value, unless it's run with a Bash version
+	supporting BASH_XTRACEFD, i.e. v4.1 or later.
 
 -d::
 --debug::
@@ -452,6 +453,22 @@ Don't:
    causing the next test to start in an unexpected directory.  Do so
    inside a subshell if necessary.
 
+ - save and verify the standard error of compound commands, i.e. group
+   commands, subshells, and shell functions (except test helper
+   functions like 'test_must_fail') like this:
+
+     ( cd dir && git cmd ) 2>error &&
+     test_cmp expect error
+
+   When running the test with '-x' tracing, then the trace of commands
+   executed in the compound command will be included in standard error
+   as well, quite possibly throwing off the subsequent checks examining
+   the output.  Instead, save only the relevant git command's standard
+   error:
+
+     ( cd dir && git cmd 2>../error ) &&
+     test_cmp expect error
+
  - Break the TAP output
 
    The raw output from your test may be interpreted by a TAP harness. TAP