Re: [PATCH v2] clone: Don't segfault on -b specifing a non-commit
- From
Jeff King <peff@peff.net>
- Date
- Nov 5, 2019, 04:37 UTC
- Message-ID
- <20191105043749.GA27601@sigill.intra.peff.net>
- In-Reply-To
- <20191103180716.GA72007@carpenter.lan>
On Sun, Nov 03, 2019 at 06:07:18PM +0000, Davide Berardi wrote:
Show 29 quoted lines
> -static void update_head(const struct ref *our, const struct ref *remote,
> +static struct commit *lookup_commit_helper(const struct ref *our,
> + const struct ref *remote,
> + const char *msg, int *err)
> +{
> + const struct object_id *tip = NULL;
> + struct commit *tip_commit = NULL;
> +
> + if (our)
> + tip = &our->old_oid;
> + else if (remote)
> + tip = &remote->old_oid;
> +
> + if (!tip)
> + return NULL;
> +
> + tip_commit = lookup_commit_reference_gently_err(the_repository, tip, 1, err);
> + if (!tip_commit) {
> + /*
> + * The given non-commit cannot be checked out,
> + * so have a 'master' branch and leave it unborn.
> + */
> + warning(_("non-commit cannot be checked out"));
> + create_symref("HEAD", "refs/heads/master", msg);
> + return NULL;
> + }
> +
> + return tip_commit;
> +}I like the logic flow in this function, which is IMHO clearer than the existing code. But the "err" thing puzzled me for a moment. I think you are trying to tell the difference between the case that both "our" and "remote" are NULL, and the case that we saw a non-commit. In either case we return NULL, but only one is an error.
But:
- I don't think that logic needs to extend down into
lookup_commit_reference_gently(); a NULL return from it would always
be an error, wouldn't it? - we could probably simplify this by just inlining it into
update_head(). Something like: if (our)
tip = &our->old_oid;
else if (remote)
tip = &remote->old_oid; if (!tip) {
/*
* We have no local branch requested with "-b", and the
* remote HEAD is unborn. There's nothing to update HEAD
* to, but this state is not an error.
*/
return 0;
} tip_commit = lookup_commit_reference_gently(...);
if (!tip_commit) {
/*
* The given non-commit cannot be checked out, etc...
*/
warning(...);
create_symref(...);
return -1;
}...and then existing code to use tip_commit...
/*
* we'd always return 0 here, because our update_ref calls die on
* error
*/
return 0;Show 10 quoted lines
> @@ -1268,8 +1303,10 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
> }
>
> junk_mode = JUNK_LEAVE_REPO;
> - fetch_if_missing = 1;
> - err = checkout(submodule_progress);
> + if (!err) {
> + fetch_if_missing = 1;
> + err = checkout(submodule_progress);
> + }This part makes sense. We might want an explanatory comment along the lines of:
/*
* Only try to checkout if we successfully updated HEAD; otherwise
* HEAD isn't pointing to the thing the user wanted.
/
if (!err) {
...
> -struct commit *lookup_commit_reference_gently(struct repository *r, > - const struct object_id *oid, int quiet) > +struct commit *lookup_commit_reference_gently_err(struct repository *r, > + const struct object_id *oid, int quiet, int *err)
And this part I think could just go away, if you take my suggestion above.
Show 13 quoted lines
> diff --git a/t/t5609-clone-branch.sh b/t/t5609-clone-branch.sh > index 6e7a7be052..d57f750eeb 100755 > --- a/t/t5609-clone-branch.sh > +++ b/t/t5609-clone-branch.sh > @@ -20,7 +20,10 @@ test_expect_success 'setup' ' > echo one >file && git add file && git commit -m one && > git checkout -b two && > echo two >file && git add file && git commit -m two && > - git checkout master) && > + git checkout master && > + blob=$(git rev-parse HEAD:file) && > + echo $blob > .git/refs/heads/broken-tag && > + echo $blob > .git/refs/heads/broken-head) &&
Minor style nit, but we usually avoid the space after ">".
Show 10 quoted lines
> +test_expect_success 'clone -b with a non-commit tag must fallback' ' > + test_must_fail git clone -b broken-tag parent clone-broken-tag && > + (cd clone-broken-tag && > + check_HEAD master) > +' > +test_expect_success 'clone -b with a non-commit head must fallback' ' > + test_must_fail git clone -b broken-head parent clone-broken-head && > + (cd clone-broken-head && > + check_HEAD master) > +'
OK, this second one covers the first conditional from update_head():
if (our && skip_prefix(our->name, "refs/heads/", &head)) {and the first one covers the second conditional:
} else if (our) {Should we cover the third conditional, too?
I think it would be the case that the remote HEAD is pointing to a non-commit (since that's a corrupt repository, it might make sense create a separate sub-repository).
-Peff