[lit] add a -vv option to echo all executed commands.

Debugging LIT scripts can be rather painful, as LIT directly does not
specify which line has failed.
Rather, FileCheck is expected to report the failing location, but it can
be often ambiguous if multiple commands are tested against the same
prefix.  This change adds a -vv option, which echoes all output.
Then detecting the error becomes straightforward: last printed line is
the failing one.

Of course, it could be desired to try to get failing line number
directly from bash, but it involves excessive hacks on older bash
versions (cf.
https://stackoverflow.com/questions/24398691/how-to-get-the-real-line-number-of-a-failing-bash-command)

Differential Revision: https://reviews.llvm.org/D35330

llvm-svn: 307938

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/docs/CommandGuide/lit.rst b/llvm/docs/CommandGuide/lit.rst
index b4d15ef57b7..fbe1a9ab184 100644
--- a/llvm/docs/CommandGuide/lit.rst
+++ b/llvm/docs/CommandGuide/lit.rst
@@ -80,6 +80,13 @@ OUTPUT OPTIONS
  Show more information on test failures, for example the entire test output
  instead of just the test result.
 
+.. option:: -vv, --echo-all-commands
+
+ Echo all commands to stdout, as they are being executed.
+ This can be valuable for debugging test failures, as the last echoed command
+ will be the one which has failed.
+ This option implies ``--verbose``.
+
 .. option:: -a, --show-all
 
  Show more information about all tests, for example the entire test