Re: [PATCH 3/3] merge-ort: implement merge_incore_recursive()
"Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com> writes:
Show 17 quoted lines
> +/*
> + * Originally from merge_recursive_internal(); somewhat adapted, though.
> + */
> +static void merge_ort_internal(struct merge_options *opt,
> + struct commit_list *merge_bases,
> + struct commit *h1,
> + struct commit *h2,
> + struct merge_result *result)
> +{
> + struct commit_list *iter;
> + struct commit *merged_merge_bases;
> + const char *ancestor_name;
> + struct strbuf merge_base_abbrev = STRBUF_INIT;
> +
> + if (!merge_bases) {
> + merge_bases = get_merge_bases(h1, h2);
> + merge_bases = reverse_commit_list(merge_bases);Do we want to say why we reverse here, or is the reason so well known why in the original merge-recursive case?
Show 21 quoted lines
> + }
> +
> + merged_merge_bases = pop_commit(&merge_bases);
> + if (merged_merge_bases == NULL) {
> + /* if there is no common ancestor, use an empty tree */
> + struct tree *tree;
> +
> + tree = lookup_tree(opt->repo, opt->repo->hash_algo->empty_tree);
> + merged_merge_bases = make_virtual_commit(opt->repo, tree,
> + "ancestor");
> + ancestor_name = "empty tree";
> + } else if (opt->ancestor && !opt->priv->call_depth) {
> + ancestor_name = opt->ancestor;
> + } else if (merge_bases) {
> + ancestor_name = "merged common ancestors";
> + } else {
> + strbuf_add_unique_abbrev(&merge_base_abbrev,
> + &merged_merge_bases->object.oid,
> + DEFAULT_ABBREV);
> + ancestor_name = merge_base_abbrev.buf;
> + }So, up to this point we learned:
- merge bases either given by the caller, or computed from h1 and
h2 when the caller just told us to figure it out ourselves.
- if we have
- 0 merge base between h1 and h2, in which case we would use an
empty tree as an imaginary common - 1 merge base between h1 and h2, in which case the common
ancestor of the resuting merge between h1 and h2 is that single
merge base - 2 or more bases, in which case we'd use that would eventually
come back when we merged recursively all bases.and the primary products of the above procedure are
- ancestor_name (the string used when presenting conflicts while
merging h1 and h2)
- merged_merge_bases (one starting commit among the merge bases)
And then the loop will iterate over the remaining merge bases, merging one popped from it in the current merged_merge_bases, until we run out. At that point when we leave the loop, we'd have merged_merge_bases that is a virtual commit to be used as a single merge base to use while merging trees of h1 and h2.
Show 30 quoted lines
> + for (iter = merge_bases; iter; iter = iter->next) {
> + const char *saved_b1, *saved_b2;
> + struct commit *prev = merged_merge_bases;
> +
> + opt->priv->call_depth++;
> + /*
> + * When the merge fails, the result contains files
> + * with conflict markers. The cleanness flag is
> + * ignored (unless indicating an error), it was never
> + * actually used, as result of merge_trees has always
> + * overwritten it: the committed "conflicts" were
> + * already resolved.
> + */
> + saved_b1 = opt->branch1;
> + saved_b2 = opt->branch2;
> + opt->branch1 = "Temporary merge branch 1";
> + opt->branch2 = "Temporary merge branch 2";
> + merge_ort_internal(opt, NULL, prev, iter->item, result);
> + if (result->clean < 0)
> + return;
> + opt->branch1 = saved_b1;
> + opt->branch2 = saved_b2;
> + opt->priv->call_depth--;
> +
> + merged_merge_bases = make_virtual_commit(opt->repo,
> + result->tree,
> + "merged tree");
> + commit_list_insert(prev, &merged_merge_bases->parents);
> + commit_list_insert(iter->item,
> + &merged_merge_bases->parents->next);We need to record these parents because...? When merged_merge_bases we just created is used as one side of a merge in the next iteration, we'd need to compute the merge base between it and the one we'd pop out of merge_bases, and that is why.
> + clear_or_reinit_internal_opts(opt->priv, 1);
> + }
OK. I think I understood this loop. It looks mostly straight-forward.
> + opt->ancestor = ancestor_name;
And the label to be used, that was computed before the above loop, is used here...
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> + merge_ort_nonrecursive_internal(opt,
> + repo_get_commit_tree(opt->repo,
> + merged_merge_bases),
> + repo_get_commit_tree(opt->repo, h1),
> + repo_get_commit_tree(opt->repo, h2),
> + result);
... to finally compute the 3-way merge between h1 and h2.
> + strbuf_release(&merge_base_abbrev);
And the storage that may have been holding the .ancestor name is cleared, as we no longer need it.
Show 15 quoted lines
> + opt->ancestor = NULL; /* avoid accidental re-use of opt->ancestor */
> +}
> +
> void merge_incore_nonrecursive(struct merge_options *opt,
> struct tree *merge_base,
> struct tree *side1,
> @@ -1493,7 +1577,9 @@ void merge_incore_recursive(struct merge_options *opt,
> struct commit *side2,
> struct merge_result *result)
> {
> - (void)reverse_commit_list;
> - (void)make_virtual_commit;
> - die("Not yet implemented");
> + assert(opt->ancestor == NULL ||
> + !strcmp(opt->ancestor, "constructed merge base"));Where does this string come from? The recursive backend does asssign a fixed string with that value to opt->ancestor, but we don't expect that string to come here, no?
> + merge_start(opt, result);
> + merge_ort_internal(opt, merge_bases, side1, side2, result);
> }
Elijah Newren via GitGitGadget
