test-tool: add unit test suite runner

For various reasons (see discussion at [1]) we would like an alternative to prove for running test suites (including the unit tests) on Windows.

[1] https://lore.kernel.org/git/[email protected]/

This series extends the existing test-tool run-command testsuite to support running unit tests. In addition, it includes some small cleanups:
* move t-basic out of the unit-tests directory
* don't hardcode the shell for running tests in test-tool ... testsuite
* don't hardcode a test name filter in test-tool ... testsuite
* add a test wrapper script to allow unit tests and the shell test suite to run in a single prove process

Changes in V4:
* Set TEST_SHELL_PATH when running the prove test target, and error out of run-test.sh if TEST_SHELL_PATH is not set.

Changes in V3:
* Added new patch (#7) to use the new test-tool runner for unit tests in Windows CI.
* Restored the explicit sort call in t/Makefile, for backwards compatibility with older GNU Make versions.
* Rebased the series on the latest jk/unit-tests-buildfix branch.
* Fixed header include order in patch #1.
* Removed a paragraph in patch #1's commit message that is obsolete now that we're building the list of test files from the sources rather than by globbing.
* Added a note in patch #2 that setting a NULL suite.shell_path will be used in a later commit.
* Clarified up some sloppy wording in commit messages and comments in t/helper/test-run-command.c.

Changes in V2:
* Rebased the series on the latest jk/unit-tests-buildfix branch.
* Patch 1: move t-basic to a test-tool subcommand rather than a new executable under t/t0080/
* New patch 2: get the shell path from TEST_SHELL_PATH in test-tool run-command testsuite
* New patch 3: remove the hardcoded filename filter in test-tool run-command testsuite
* Patch 4 (previously 2): simplified now that we no longer need to add any command-line flags to support unit tests
* Patch 5 (previously 3): avoid trying to run cmake *.pdb files by using the unit test list built in the makefile in jk/unit-tests-buildfix.

Jeff King (1):
t/Makefile: run unit tests alongside shell tests

Josh Steadmon (6):
t0080: turn t-basic unit test into a helper test-tool run-command testsuite: get shell from env test-tool run-command testsuite: remove hardcoded filter test-tool run-command testsuite: support unit tests unit tests: add rule for running with test-tool
ci: use test-tool as unit test runner on Windows

 Makefile                                      |  6 ++--
 ci/run-build-and-tests.sh                     |  2 --
 ci/run-test-slice.sh                          |  2 +-
 t/Makefile                                    | 14 ++++++++--
 .../t-basic.c => helper/test-example-tap.c}   |  5 ++--
 t/helper/test-run-command.c                   | 28 +++++++++++++++----
 t/helper/test-tool.c                          |  1 +
 t/helper/test-tool.h                          |  1 +
 t/run-test.sh                                 | 18 ++++++++++++
 t/t0080-unit-test-output.sh                   | 24 ++++++++--------
 10 files changed, 72 insertions(+), 29 deletions(-)
 rename t/{unit-tests/t-basic.c => helper/test-example-tap.c} (95%)
 create mode 100755 t/run-test.sh

Range-diff against v5:

1:  6777451100 = 1:  6777451100 t0080: turn t-basic unit test into a helper
2:  24f47f8fc7 = 2:  24f47f8fc7 test-tool run-command testsuite: get shell from env
3:  4a16a3ec24 = 3:  4a16a3ec24 test-tool run-command testsuite: remove hardcoded filter
4:  abc9a7afe8 = 4:  abc9a7afe8 test-tool run-command testsuite: support unit tests
5:  a8bbff2c6b = 5:  a8bbff2c6b unit tests: add rule for running with test-tool
6:  c6606446c4 ! 6:  dae670fcb1 t/Makefile: run unit tests alongside shell tests
    @@ t/run-test.sh (new)
     +
     +case "$1" in
     +*.sh)
    -+  if test -z "${TEST_SHELL_PATH+set}"
    ++  if test -z "${TEST_SHELL_PATH}"
     +  then
     +          echo >&2 "ERROR: TEST_SHELL_PATH is empty or not set"
     +          exit 1
     +  fi
    -+  exec ${TEST_SHELL_PATH} "$@"
    ++  exec "${TEST_SHELL_PATH}" "$@"
     +  ;;
     +*)
     +  exec "$@"

7: 4a92131ab9 = 7: 2f5853a7fa ci: use test-tool as unit test runner on Windows

base-commit: 4904a4d08cc085716df12ce713ae7ee3d5ecb75a

2.45.0.rc1.225.g2a3ae87e7f-goog