Eric Sunshine [off-list ref] writes:

quoted

diff --git a/t/t3310-notes-merge-manual-resolve.sh b/t/t3310-notes-merge-manual-resolve.sh

@@ -569,13 +578,15 @@ EOF
        test_grep -q "refs/notes/m" output &&
-       test_grep -q "$(git rev-parse refs/notes/m)" output &&
-       test_grep -q "$(git rev-parse NOTES_MERGE_PARTIAL^1)" output &&
+       git rev-parse refs/notes/m >actual &&
+       test_grep -q "$(cat actual)" output &&
+       git rev-parse NOTES_MERGE_PARTIAL^1 >actual &&
+       test_grep -q "$(cat actual)" output &&

Storing the output of git-rev-parse in a file only to read it back out
of that file a moment later is unnecessarily roundabout. It would
instead be cleaner to do it this way:

    oid=$(git rev-parse refs/notes/m) &&
    test_grep -q "$oid" output &&
    oid=$(git rev-parse NOTES_MERGE_PARTIAL^1) &&
    test_grep -q "$oid" output &&

Unlike this original in which git-rev-parse's exit code was lost due
to being embedded in the test_grep invocation, this rewrite is safe
because the exit code of git-rev-parse becomes the exit code of the
variable assignment, thus correctly aborts the test (due to the
&&-chain) if git-rev-parse fails.

quoted

@@ -606,8 +617,9 @@ test_expect_success 'switch cwd before committing notes merge' '
        test_must_fail git notes merge refs/notes/other &&
        (
                cd .git/NOTES_MERGE_WORKTREE &&
-               echo "foo" > $(git rev-parse HEAD) &&
-               echo "bar" >> $(git rev-parse HEAD) &&
+               oid=$(git rev-parse HEAD) &&
+               echo "foo" >"$oid" &&
+               echo "bar" >>"$oid" &&

This is purely subjective and you don't have to take the suggestion,
but although yours is a faithful rewrite (which is good), I probably
would have simplified this to:

    oid=$(git rev-parse HEAD) &&
    test_write_lines foo bar >"$oid" &&

Thanks for the review. Both suggestions make sense. I'll use the
variable assignment for the rev-parse cases and test_write_lines for
the foo/bar case. I will send v4 shortly.