t7610: use "file:///dev/null", not "/dev/null", fixes MinGW

On MinGW the "/dev/null" is translated to "nul" on command-lines, even
though as in this case it'll never end up referring to an actual file.

So on Windows the fix for the previous "example.com" timeout issue in
8354cf752ec (t7610: fix flaky timeout issue, don't clone from
example.com, 2022-11-05) would yield:

  fatal: repo URL: 'nul' must be absolute or begin with ./|../

Let's evade this yet again by prefixing this with "file://", which
makes this pass in the Windows CI.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>

diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
index b1ba0d9a088219c9250539ec49afad233bad4ae1..7b957022f1abbd0b01cf043b52ebfd8a76042929 100755 (executable)
--- a/t/t7610-mergetool.sh
+++ b/t/t7610-mergetool.sh
@@ -33,7 +33,7 @@ test_expect_success 'setup' '
                git add foo &&
                git commit -m "Add foo"
        ) &&
-       git submodule add /dev/null submod &&
+       git submodule add file:///dev/null submod &&
        git add file1 "spaced name" file1[1-4] subdir/file3 .gitmodules submod &&
        git commit -m "add initial versions" &&
 
@@ -614,7 +614,7 @@ test_expect_success 'submodule in subdirectory' '
                )
        ) &&
        test_when_finished "rm -rf subdir/subdir_module" &&
-       git submodule add /dev/null subdir/subdir_module &&
+       git submodule add file:///dev/null subdir/subdir_module &&
        git add subdir/subdir_module &&
        git commit -m "add submodule in subdirectory" &&