tests: explicitly use git.exe on Windows

On Windows, when we refer to `/an/absolute/path/to/git`, it magically
resolves `git.exe` at that location. Except if something of the name
`git` exists next to that `git.exe`. So if we call `$BUILD_DIR/git`, it
will find `$BUILD_DIR/git.exe` *only* if there is not, say, a directory
called `$BUILD_DIR/git`.

Such a directory, however, exists in Git for Windows when building with
Visual Studio (our Visual Studio project generator defaults to putting
the build files into a directory whose name is the base name of the
corresponding `.exe`).

In the bin-wrappers/* scripts, we already take pains to use `git.exe`
rather than `git`, as this could pick up the wrong thing on Windows
(i.e. if there exists a `git` file or directory in the build directory).

Now we do the same in the tests' start-up code.

This also helps when testing an installed Git, as there might be even
more likely some stray file or directory in the way.

Note: the only way we can record whether the `.exe` suffix is by writing
it to the `GIT-BUILD-OPTIONS` file and sourcing it at the beginning of
`t/test-lib.sh`. This is not a requirement introduced by this patch, but
we move the call to be able to use the `$X` variable that holds the file
extension, if any.

Note also: the many, many calls to `git this` and `git that` are
unaffected, as the regular PATH search will find the `.exe` files on
Windows (and not be confused by a directory of the name `git` that is
in one of the directories listed in the `PATH` variable), while
`/path/to/git` would not, per se, know that it is looking for an
executable and happily prefer such a directory.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: dscho

Makefile

@@ -2591,6 +2591,7 @@ GIT-BUILD-OPTIONS: FORCE
 	@echo NO_UNIX_SOCKETS=\''$(subst ','\'',$(subst ','\'',$(NO_UNIX_SOCKETS)))'\' >>$@+
 	@echo PAGER_ENV=\''$(subst ','\'',$(subst ','\'',$(PAGER_ENV)))'\' >>$@+
 	@echo DC_SHA1=\''$(subst ','\'',$(subst ','\'',$(DC_SHA1)))'\' >>$@+
+	@echo X=\'$(X)\' >>$@+
 ifdef TEST_OUTPUT_DIRECTORY
 	@echo TEST_OUTPUT_DIRECTORY=\''$(subst ','\'',$(subst ','\'',$(TEST_OUTPUT_DIRECTORY)))'\' >>$@+
 endif

t/test-lib-functions.sh

@@ -923,7 +923,7 @@ test_create_repo () {
 	mkdir -p "$repo"
 	(
 		cd "$repo" || error "Cannot setup test environment"
-		"${GIT_TEST_INSTALLED:-$GIT_EXEC_PATH}/git" init \
+		"${GIT_TEST_INSTALLED:-$GIT_EXEC_PATH}/git$X" init \
 			"--template=$GIT_BUILD_DIR/templates/blt/" >&3 2>&4 ||
 		error "cannot run git init -- have you built things yet?"
 		mv .git/hooks .git/hooks-disabled

t/test-lib.sh

@@ -49,9 +49,17 @@ export ASAN_OPTIONS
 : ${LSAN_OPTIONS=abort_on_error=1}
 export LSAN_OPTIONS
 
+if test ! -f "$GIT_BUILD_DIR"/GIT-BUILD-OPTIONS
+then
+	echo >&2 'error: GIT-BUILD-OPTIONS missing (has Git been built?).'
+	exit 1
+fi
+. "$GIT_BUILD_DIR"/GIT-BUILD-OPTIONS
+export PERL_PATH SHELL_PATH
+
 ################################################################
 # It appears that people try to run tests without building...
-"${GIT_TEST_INSTALLED:-$GIT_BUILD_DIR}/git" >/dev/null
+"${GIT_TEST_INSTALLED:-$GIT_BUILD_DIR}/git$X" >/dev/null
 if test $? != 1
 then
 	if test -n "$GIT_TEST_INSTALLED"
@@ -63,9 +71,6 @@ then
 	exit 1
 fi
 
-. "$GIT_BUILD_DIR"/GIT-BUILD-OPTIONS
-export PERL_PATH SHELL_PATH
-
 # if --tee was passed, write the output not only to the terminal, but
 # additionally to the file test-results/$BASENAME.out, too.
 case "$GIT_TEST_TEE_STARTED, $* " in