Re: [PATCH] [GSOC] ref-filter: add contents:raw atom

[ZheNing Hu <adlternative@gmail.com>]

Christian Couder <christian.couder@gmail.com> 于2021年5月21日周五 上午12:20写道：
>
> On Thu, May 20, 2021 at 10:49 AM ZheNing Hu via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> >
> > From: ZheNing Hu <adlternative@gmail.com>
> >
> > Add new formatting option %(contents:raw), which will
> > print all the object contents without any changes.
>
> Maybe you could tell how it would be different from %(contents), or in
> other words what are the changes that %(contents) makes.
>
> Isn't %(contents) only printing the commit message or the tag message
> of a commit or a tag respectively? If %(contents:raw) would print all
> the object contents, it could feel strange that it is actually
> printing more than %(contents).
>

Okay, some explanations are indeed missing here:

%(contents) will discard the metadata part of the object file,
and only print the data contents part of it. %(contents:raw)
can will not discard the metadata part of the object file, this
 means that it can print the "raw" content of an object.

In addition, %(contents:raw) can support print commit, blob,
tag, tree objects contents which %(contents) can only support
commit,tag objects.

E.g:

git for-each-ref --format=%(contents:raw) refs/heads/foo

will have the same output as:

git rev-parse refs/heads/foo | git cat-file --batch

> Also is %(contents:raw) supposed to print something for a blob or a
> tree, while I guess %(contents) is printing nothing for them?
>

Now my thoughts are:
Let %(contents) learn to print four kinds of objects.
and then let %(contents:raw) learn to print metadata.
I will split it into two patches.

> > It will help further to migrate all cat-file formatting
> > logic from cat-file to ref-filter.
> >
> > Signed-off-by: ZheNing Hu <adlternative@gmail.com>
>
> It looks like you rewrote the patch nearly completely, but if you
> based your patch on, or got inspired by, Olga's work, it might be nice
> to acknowledge this using a trailer (for example "Based-on-patch-by:
> ..." or "Helped-by:...").
>

Okay, "Based-on-patch-by" would be more appropriate here.

> > @@ -1312,6 +1315,13 @@ static void grab_sub_body_contents(struct atom_value *val, int deref, void *buf)
> >                     !starts_with(name, "trailers") &&
> >                     !starts_with(name, "contents"))
> >                         continue;
> > +               if (atom->u.contents.option == C_RAW) {
> > +                       v->s = xmemdupz(buf, buf_size);
> > +                       continue;
> > +               }
> > +               if (object_type != OBJ_TAG && object_type != OBJ_COMMIT)
> > +                       continue;
>
> When seeing the 2 lines above, I am guessing that, before this patch,
> grab_sub_body_contents() couldn't actually be called when object_type
> was OBJ_BLOB or OBJ_TREE, but you have made other changes elsewhere so
> that now it can. As only the atom->u.contents.option == C_RAW case is
> relevant in this case, you added this check. Let's see if I am
> right...
>
> >                 if (!subpos)
> >                         find_subpos(buf,
> >                                     &subpos, &sublen,
> > @@ -1374,25 +1384,30 @@ static void fill_missing_values(struct atom_value *val)
> >   * pointed at by the ref itself; otherwise it is the object the
> >   * ref (which is a tag) refers to.
> >   */
> > -static void grab_values(struct atom_value *val, int deref, struct object *obj, void *buf)
> > +static void grab_values(struct atom_value *val, int deref, struct object *obj, struct expand_data *data)
> >  {
> > +       void *buf = data->content;
> > +       unsigned long buf_size = data->size;
> > +
> >         switch (obj->type) {
> >         case OBJ_TAG:
> >                 grab_tag_values(val, deref, obj);
> > -               grab_sub_body_contents(val, deref, buf);
> > +               grab_sub_body_contents(val, deref, buf, buf_size, obj->type);
> >                 grab_person("tagger", val, deref, buf);
> >                 break;
> >         case OBJ_COMMIT:
> >                 grab_commit_values(val, deref, obj);
> > -               grab_sub_body_contents(val, deref, buf);
> > +               grab_sub_body_contents(val, deref, buf, buf_size, obj->type);
> >                 grab_person("author", val, deref, buf);
> >                 grab_person("committer", val, deref, buf);
> >                 break;
> >         case OBJ_TREE:
> >                 /* grab_tree_values(val, deref, obj, buf, sz); */
> > +               grab_sub_body_contents(val, deref, buf, buf_size, obj->type);
> >                 break;
> >         case OBJ_BLOB:
> >                 /* grab_blob_values(val, deref, obj, buf, sz); */
> > +               grab_sub_body_contents(val, deref, buf, buf_size, obj->type);
>
> ...ok, I was right above. The issue now is that I wonder if
> grab_sub_body_contents() is still a good name for a function that can
> be called for a blob or a tree which does not really have a body.
>

Makes sense, It might be better to use the new name: grab_contents().

> >                 break;
> >         default:
> >                 die("Eh?  Object of type %d?", obj->type);
> > @@ -1614,7 +1629,7 @@ static int get_object(struct ref_array_item *ref, int deref, struct object **obj
> >                         return strbuf_addf_ret(err, -1, _("parse_object_buffer failed on %s for %s"),
> >                                                oid_to_hex(&oi->oid), ref->refname);
> >                 }
> > -               grab_values(ref->value, deref, *obj, oi->content);
> > +               grab_values(ref->value, deref, *obj, oi);
> >         }
> >
> >         grab_common_values(ref->value, deref, oi);
> > diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
> > index 9e0214076b4d..baa3a40a70b1 100755
> > --- a/t/t6300-for-each-ref.sh
> > +++ b/t/t6300-for-each-ref.sh
> > @@ -686,6 +686,17 @@ test_atom refs/tags/signed-empty contents:body ''
> >  test_atom refs/tags/signed-empty contents:signature "$sig"
> >  test_atom refs/tags/signed-empty contents "$sig"
> >
> > +test_expect_success 'basic atom: refs/tags/signed-empty contents:raw' '
> > +       git cat-file tag refs/tags/signed-empty >expected &&
> > +       git for-each-ref --format="%(contents:raw)" refs/tags/signed-empty >actual &&
> > +       sanitize_pgp <expected >expected.clean &&
> > +       sanitize_pgp <actual >actual.clean &&
> > +       echo "" >>expected.clean &&
> > +       test_cmp expected.clean actual.clean
> > +'
>
> For an empty tag %(contents:raw) should produce nothing, ok.
>
> > +test_atom refs/tags/signed-empty *contents:raw $(git cat-file commit HEAD)
>
> Maybe use single quotes around *contents:raw?
>
> The rest looks good to me. Thanks!

Good suggestion. thank!
--
ZheNing Hu