[PATCH 3/4] qemu-iotests: let "check" spawn an arbitrary test command

[Paolo Bonzini <pbonzini@redhat.com>]

Right now there is no easy way for "check" to print a reproducer command.
Because such a reproducer command line would be huge, we can instead teach
check to start a command of our choice.  This can be for example a Python
unit test with arguments to only run a specific subtest.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tests/qemu-iotests/check | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/tests/qemu-iotests/check b/tests/qemu-iotests/check
index d1c87ceaf1..aab25dac6a 100755
--- a/tests/qemu-iotests/check
+++ b/tests/qemu-iotests/check
@@ -19,6 +19,7 @@
 import os
 import sys
 import argparse
+import shutil
 from findtests import TestFinder
 from testenv import TestEnv
 from testrunner import TestRunner
@@ -100,8 +101,8 @@ def make_argparser() -> argparse.ArgumentParser:
                        'one to TEST (not inclusive). This may be used to '
                        'rerun failed ./check command, starting from the '
                        'middle of the process.')
-    g_sel.add_argument('tests', metavar='TEST_FILES', nargs='*',
-                       help='tests to run')
+    g_sel.add_argument('tests', nargs=argparse.REMAINDER,
+                       help='tests to run, or "--" followed by a command')
 
     return p
 
@@ -114,6 +115,17 @@ if __name__ == '__main__':
                   imgopts=args.imgopts, misalign=args.misalign,
                   debug=args.debug, valgrind=args.valgrind)
 
+    if args.tests[0] == '--':
+        del args.tests[0]
+        cmd = args.tests
+        env.print_env()
+        exec_path = shutil.which(cmd[0])
+        if exec_path is None:
+            sys.exit('command not found: ' + cmd[0])
+        cmd[0] = exec_path
+        full_env = env.prepare_subprocess(cmd)
+        os.execve(cmd[0], cmd, full_env)
+
     testfinder = TestFinder(test_dir=env.source_iotests)
 
     groups = args.groups.split(',') if args.groups else None
-- 
2.30.1