Xiaolong Ye <xiaolong.ye@xxxxxxxxx> writes:
> +static struct commit *get_base_commit(const char *base_commit,
> + struct commit **list,
> + int total)
> +{
> + struct commit *base = NULL;
> + struct commit **rev;
> + int i = 0, rev_nr = 0;
> +
> + base = lookup_commit_reference_by_name(base_commit);
> + if (!base)
> + die(_("Unknown commit %s"), base_commit);
> +
> + ALLOC_ARRAY(rev, total);
> + for (i = 0; i < total; i++)
> + rev[i] = list[i];
> +
> + rev_nr = total;
> + /*
> + * Get merge base through pair-wise computations
> + * and store it in rev[0].
> + */
> + while (rev_nr > 1) {
> + for (i = 0; i < rev_nr / 2; i++) {
> + struct commit_list *merge_base;
> + merge_base = get_merge_bases(rev[2 * i], rev[2 * i + 1]);
> + if (!merge_base || merge_base->next)
> + die(_("Failed to find exact merge base"));
> +
> + rev[i] = merge_base->item;
> + }
So merge-base(0,1) is stored in rev[0], merge-base(2,3) is then
stored in rev[1], etc. and the last item, if rev_nr is odd, is left
in rev[rev_nr-1]. When the loop finishes, i is left as rev_nr/2
and...
> + if (rev_nr % 2)
> + rev[i] = rev[2 * i];
... when rev_nr is odd, that left-over thing moved down here.
E.g. if rev_nr == 5, the loop is left with i==2, rev[0] and rev[1]
are filled with pairwise merge bases, and this moves rev[4] to
rev[2], so that we can further process rev[0,1,2] with rev_nr set to
3 (i.e. (rev_nr + 1) / 2 below).
Sounds correct.
> + rev_nr = (rev_nr + 1) / 2;
> + }
> +
> + if (!in_merge_bases(base, rev[0]))
> + die(_("base commit should be the ancestor of revision list"));
> +
> + for (i = 0; i < total; i++) {
> + if (base == list[i])
> + die(_("base commit shouldn't be in revision list"));
> + }
> +
> + free(rev);
> + return base;
> +}
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