Re: [PATCH] fast-import: properly fanout notes when tree is imported

> In typical uses of fast-import, trees are inherited from a parent
> commit. In that case, the tree_entry for the branch looks like:
>
>   .versions[1].sha1 = $some_sha1
>   .tree = <tree structure loaded from $some_sha1>
>
> However, when trees are imported, rather than inherited, that is not the
> case. One can import a tree with a filemodify command, replacing the
> root tree object.
>
> e.g.
>   "M 040000 $some_sha1 \n"
>
> In this case, the tree_entry for the branch looks like:
>
>   .versions[1].sha1 = $some_sha1
>   .tree = NULL
>
> When adding new notes with the notemodify command, do_change_note_fanout
> is called to get a notes count, and to do so, it loops over the
> tree_entry->tree, but doesn't do anything when the tree is NULL.
>
> In the latter case above, it means do_change_note_fanout thinks the tree
> contains no note, and new notes are added with no fanout.

>
> Interestingly, do_change_note_fanout does check whether subdirectories
> have a NULL .tree, in which case it uses load_tree(). Which means the
> right behaviour happens when using the filemodify command to import
> subdirectories.
>
> This change makes do_change_note_fanount call load_tree() whenever the
> tree_entry it is given has no tree loaded, making all cases handled
> equally.
>
> Signed-off-by: Mike Hommey <mh@glandium.org>