builtin/describe.c:91:23: error: incomplete definition of type 'struct tag'
                if (e->tag->date < t->date)
                                   ~^

builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
builtin/describe.c:215:10: warning: incompatible integer to pointer conversion assigning to 'struct tag *'
      from 'int' [-Wint-conversion]
                n->tag = lookup_tag(n->sha1);
                       ^ ~~~~~~~~~~~~~~~~~~~
builtin/describe.c:220:14: error: incomplete definition of type 'struct tag'
                if (!n->tag->tag)
                     ~~~~~~^
builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
builtin/describe.c:222:20: error: incomplete definition of type 'struct tag'
                if (strcmp(n->tag->tag, all ? n->path + 5 : n->path))
                           ~~~~~~^
builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
builtin/describe.c:223:53: error: incomplete definition of type 'struct tag'
                        warning(_("tag '%s' is really '%s' here"), n->tag->tag, n->path);
                                                                   ~~~~~~^
builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
builtin/describe.c:228:22: error: incomplete definition of type 'struct tag'
                printf("%s", n->tag->tag);
                             ~~~~~~^

builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
builtin/describe.c:262:34: error: incomplete definition of type 'struct tag'
                        show_suffix(0, n->tag ? n->tag->tagged->sha1 : sha1);
                                                ~~~~~~^
builtin/describe.c:43:9: note: forward declaration of 'struct tag'
        struct tag *tag;
               ^
5 warnings and 7 errors generated.
gmake: *** [builtin/describe.o] Error 1