Re: [PATCH v2 3/5] t4301: verify that merge-tree fails on missing blob objects

[Eric Sunshine <sunshine@sunshineco.com>]

On Wed, Feb 7, 2024 at 11:48 AM Johannes Schindelin via GitGitGadget
<gitgitgadget@gmail.com> wrote:
> We just fixed a problem where `merge-tree` would not fail on missing
> tree objects. Let's ensure that that problem does not occur with blob
> objects (and won't, in the future, either).
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
> diff --git a/t/t4301-merge-tree-write-tree.sh b/t/t4301-merge-tree-write-tree.sh
> @@ -961,4 +961,18 @@ test_expect_success 'error out on missing tree objects' '
> +test_expect_success 'error out on missing blob objects' '
> +       seq1=$(test_seq 1 10 | git hash-object -w --stdin) &&
> +       seq2=$(test_seq 1 11 | git hash-object -w --stdin) &&
> +       seq3=$(test_seq 0 10 | git hash-object -w --stdin) &&

Is there significance to the ranges passed to test_seq()? Or, can the
same be achieved by using arbitrary content for each blob?

    blob1=$(echo "one" | git hash-object -w --stdin) &&
    blob2=$(echo "two" | git hash-object -w --stdin) &&
    blob3=$(echo "three" | git hash-object -w --stdin) &&

> +       tree1=$(printf "100644 blob %s\tsequence" $seq1 | git mktree) &&
> +       tree2=$(printf "100644 blob %s\tsequence" $seq2 | git mktree) &&
> +       tree3=$(printf "100644 blob %s\tsequence" $seq3 | git mktree) &&

I found the lack of terminating "\n" in the `printf` confusing,
especially since the variable names (seq1, seq2, etc.) and the use of
`printf` seem to imply, at first glance, that each git-mktree
invocation is receiving multiple lines as input which, it turns out,
is not the case. Adding the missing "\n" would help:

   tree1=$(printf "100644 blob %s\tsequence\n" $seq1 | git mktree) &&
   tree2=$(printf "100644 blob %s\tsequence\n" $seq2 | git mktree) &&
   tree3=$(printf "100644 blob %s\tsequence\n" $seq3 | git mktree) &&

Interpolating the $seqN variable directly into the string rather than
using %s would make it even clearer that only a single line is being
generated as input to git-mktree:

   tree1=$(printf "100644 blob $seq1\tsequence\n" | git mktree) &&
   tree2=$(printf "100644 blob $seq2\tsequence\n" | git mktree) &&
   tree3=$(printf "100644 blob $seq3\tsequence\n" | git mktree) &&

Alternatively `echo` could be used, though it's not necessarily any nicer:

    tree1=$(echo "100644 blob $seq1Qsequence" | q_to_tab | git mktree) &&
    tree2=$(echo "100644 blob $seq2Qsequence" | q_to_tab | git mktree) &&
    tree3=$(echo "100644 blob $seq3Qsequence" | q_to_tab | git mktree) &&

> +       git init --bare missing-blob.git &&
> +       test_write_lines $seq1 $seq3 $tree1 $tree2 $tree3 |
> +       git pack-objects missing-blob.git/objects/pack/side1-whatever-is-missing &&
> +       test_must_fail git --git-dir=missing-blob.git merge-tree --merge-base=$tree1 $tree2 $tree3 >actual &&
> +       test_must_be_empty actual
> +'