merge-recursive: add a bunch of FIXME comments documenting known bugs
The plan is to just delete merge-recursive, but not until everyone is comfortable with merge-ort as a replacement. Given that I haven't switched all callers of merge-recursive over yet (e.g. git-am still uses merge-recursive), maybe there's some value documenting known bugs in the algorithm in case we end up keeping it or someone wants to dig it up in the future. Signed-off-by: Elijah Newren <newren@gmail.com> Reviewed-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Elijah Newren committed
Mar 20, 2021 at 00:03 UTC
816147e7bab0c7e9c3a578ce166c55d5f7a64a8a
1 file changed
+37
merge-recursive.c
+37
@@ -1075,6 +1075,11 @@ static int merge_3way(struct merge_options *opt,
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read_mmblob(&src1, &a->oid);
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read_mmblob(&src2, &b->oid);
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+ /*
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+ * FIXME: Using a->path for normalization rules in ll_merge could be
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+ * wrong if we renamed from a->path to b->path. We should use the
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+ * target path for where the file will be written.
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+ */
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merge_status = ll_merge(result_buf, a->path, &orig, base,
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&src1, name1, &src2, name2,
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opt->repo->index, &ll_opts);
@@ -1154,6 +1159,8 @@ static void print_commit(struct commit *commit)
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struct strbuf sb = STRBUF_INIT;
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struct pretty_print_context ctx = {0};
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ctx.date_mode.type = DATE_NORMAL;
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+ /* FIXME: Merge this with output_commit_title() */
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+ assert(!merge_remote_util(commit));
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format_commit_message(commit, " %h: %m %s", &sb, &ctx);
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fprintf(stderr, "%s\n", sb.buf);
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strbuf_release(&sb);
@@ -1177,6 +1184,11 @@ static int merge_submodule(struct merge_options *opt,
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int search = !opt->priv->call_depth;
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/* store a in result in case we fail */
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+ /* FIXME: This is the WRONG resolution for the recursive case when
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+ * we need to be careful to avoid accidentally matching either side.
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+ * Should probably use o instead there, much like we do for merging
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+ * binaries.
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+ */
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oidcpy(result, a);
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/* we can not handle deletion conflicts */
@@ -1301,6 +1313,13 @@ static int merge_mode_and_contents(struct merge_options *opt,
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if ((S_IFMT & a->mode) != (S_IFMT & b->mode)) {
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result->clean = 0;
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+ /*
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+ * FIXME: This is a bad resolution for recursive case; for
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+ * the recursive case we want something that is unlikely to
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+ * accidentally match either side. Also, while it makes
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+ * sense to prefer regular files over symlinks, it doesn't
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+ * make sense to prefer regular files over submodules.
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+ */
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if (S_ISREG(a->mode)) {
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result->blob.mode = a->mode;
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oidcpy(&result->blob.oid, &a->oid);
@@ -1349,6 +1368,7 @@ static int merge_mode_and_contents(struct merge_options *opt,
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free(result_buf.ptr);
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if (ret)
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return ret;
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+ /* FIXME: bug, what if modes didn't match? */
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result->clean = (merge_status == 0);
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} else if (S_ISGITLINK(a->mode)) {
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result->clean = merge_submodule(opt, &result->blob.oid,
@@ -2664,6 +2684,14 @@ static int process_renames(struct merge_options *opt,
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struct string_list b_by_dst = STRING_LIST_INIT_NODUP;
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const struct rename *sre;
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+ /*
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+ * FIXME: As string-list.h notes, it's O(n^2) to build a sorted
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+ * string_list one-by-one, but O(n log n) to build it unsorted and
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+ * then sort it. Note that as we build the list, we do not need to
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+ * check if the existing destination path is already in the list,
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+ * because the structure of diffcore_rename guarantees we won't
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+ * have duplicates.
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+ */
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for (i = 0; i < a_renames->nr; i++) {
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sre = a_renames->items[i].util;
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string_list_insert(&a_by_dst, sre->pair->two->path)->util
@@ -3602,6 +3630,15 @@ static int merge_recursive_internal(struct merge_options *opt,
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return err(opt, _("merge returned no commit"));
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}
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+ /*
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+ * FIXME: Since merge_recursive_internal() is only ever called by
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+ * places that ensure the index is loaded first
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+ * (e.g. builtin/merge.c, rebase/sequencer, etc.), in the common
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+ * case where the merge base was unique that means when we get here
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+ * we immediately discard the index and re-read it, which is a
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+ * complete waste of time. We should only be discarding and
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+ * re-reading if we were forced to recurse.
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+ */
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discard_index(opt->repo->index);
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if (!opt->priv->call_depth)
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repo_read_index(opt->repo);