t6423: introduce Windows-specific handling for symlinking to /dev/null

The device `/dev/null` does not exist on Windows, it's called `NUL`
there. Calling `ln -s /dev/null my-symlink` in a symlink-enabled MSYS2
Bash will therefore literally link to a file or directory called `null`
that is supposed to be in the current drive's top-level `dev` directory.
Which typically does not exist.

The test, however, really wants the created symbolic link to point to
the NUL device. Let's instead use the `mklink` utility on Windows to
perform that job, and keep using `ln -s /dev/null <target>` on
non-Windows platforms.

While at it, add the missing `SYMLINKS` prereq because this test _still_
would not pass on Windows before support for symbolic links is
upstreamed from Git for Windows.

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

diff --git a/t/t6423-merge-rename-directories.sh b/t/t6423-merge-rename-directories.sh
index 533ac85dc834092497fcdb6b36b845a2cd49519b..53535a8ebfc393723f93cecc213a0687508f70ab 100755 (executable)
--- a/t/t6423-merge-rename-directories.sh
+++ b/t/t6423-merge-rename-directories.sh
@@ -5158,13 +5158,18 @@ test_setup_12m () {
                git switch B &&
                git rm dir/subdir/file &&
                mkdir dir &&
-               ln -s /dev/null dir/subdir &&
+               if test_have_prereq MINGW
+               then
+                       cmd //c 'mklink dir\subdir NUL'
+               else
+                       ln -s /dev/null dir/subdir
+               fi &&
                git add . &&
                git commit -m "B"
        )
 }
 
-test_expect_success '12m: Change parent of renamed-dir to symlink on other side' '
+test_expect_success SYMLINKS '12m: Change parent of renamed-dir to symlink on other side' '
        test_setup_12m &&
        (
                cd 12m &&