Fix expected values of setup tests on Windows

On Windows, bash stores absolute path names in shell variables in POSIX
format that begins with a slash, rather than in drive-letter format; such
a value is converted to the latter format when it is passed to a non-MSYS
program such as git.

When an expected test value is constructed, it must contain the value that
will be produced by git, which will be in the drive-letter format. But
TRASH_DIRECTORY is in POSIX format. Fix this by using $(pwd), which
produces drive-letter format since 4114156a (Tests on Windows: $(pwd) must
return Windows-style paths).

The change in t1510 is a straight seach-and-replace, except for the first
hunk of the diff.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1501-worktree.sh

@@ -343,7 +343,7 @@ test_expect_success 'make_relative_path handles double slashes in GIT_DIR' '
 test_expect_success 'relative $GIT_WORK_TREE and git subprocesses' '
 	GIT_DIR=repo.git GIT_WORK_TREE=repo.git/work \
 	test-subprocess --setup-work-tree rev-parse --show-toplevel >actual &&
-	echo "$TRASH_DIRECTORY/repo.git/work" >expected &&
+	echo "$(pwd)/repo.git/work" >expected &&
 	test_cmp expected actual
 '