On Tue, Jun 2, 2015 at 8:57 AM, Michael Haggerty <mhagger@xxxxxxxxxxxx> wrote:
> NULL_SHA1 is never a valid value for a reference. If a loose reference
> has that value, mark it as broken.
>
> Why check NULL_SHA1 and not the nearly 2^160 other SHA-1s that are
> also invalid in a given repository? Because (a) it is cheap to test
> for NULL_SHA1, and (b) NULL_SHA1 is often used as a "SHA-1 is invalid"
I don't quite agree with the reasoning here. Just because it's cheap doesn't
mean it's right. ;) But I fully agree with (b) so this still makes sense.
> value inside of Git client source code (not only ours!), and
> accidentally writing it to a loose reference file would be an easy
> mistake to make.
>
> Signed-off-by: Michael Haggerty <mhagger@xxxxxxxxxxxx>
> ---
> refs.c | 7 +++++++
> t/t6301-for-each-ref-errors.sh | 2 +-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/refs.c b/refs.c
> index 47e4e53..c28fde1 100644
> --- a/refs.c
> +++ b/refs.c
> @@ -1321,6 +1321,13 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
> hashclr(sha1);
> flag |= REF_ISBROKEN;
> }
> +
> + if (!(flag & REF_ISBROKEN) && is_null_sha1(sha1)) {
Why do we do the extra check for !(flag & REF_ISBROKEN) here?
> + /* NULL_SHA1 is never a valid reference value. ...
... *by our definition*, because we believe it helps detecting
errors/mistakes in the future.
*/
> + hashclr(sha1);
While this code looks consistent to the rest around, at closer inspection
this feels a bit redundant to me. If is_null_sha1(sha1) is true, then
hashclr(sha1); doesn't change the state. Or did I miss a subtle side effect?
> + flag |= REF_ISBROKEN;
> + }
> +
> if (check_refname_format(refname.buf,
> REFNAME_ALLOW_ONELEVEL)) {
> hashclr(sha1);
> diff --git a/t/t6301-for-each-ref-errors.sh b/t/t6301-for-each-ref-errors.sh
> index 72d2397..cdb67a0 100755
> --- a/t/t6301-for-each-ref-errors.sh
> +++ b/t/t6301-for-each-ref-errors.sh
> @@ -24,7 +24,7 @@ test_expect_success 'Broken refs are reported correctly' '
> test_cmp broken-err err
> '
>
> -test_expect_failure 'NULL_SHA1 refs are reported correctly' '
> +test_expect_success 'NULL_SHA1 refs are reported correctly' '
> r=refs/heads/zeros &&
> echo $ZEROS >.git/$r &&
> test_when_finished "rm -f .git/$r" &&
> --
> 2.1.4
>
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