Re: [PATCH 1/1] revision.c: use new topo-order logic in tests

"Derrick Stolee via GitGitGadget" [off-list ref] writes:

That is equivalent to say

	if (git_env_bool(GIT_TEST_COMMIT_GRAPH, 0))
		revs->limited = 0;

Wouldn't that make the codepath that involves limit_list()
completely unreachable while testing, though?

The title only mentions "topo-order" logic, but the topo-order is
not the only reason why limited bit can be set, is it?  When showing
merges, simplifying merges, or post-processing to show ancestry
path, or showing a bottom-limited revision range, the limited bit is
automatically set because all of these depend on first calling
limit_list() and then postprocessing its result.  Doesn't it hurt
these cases to unconditionally drop limited bit?

On 11/20/2018 1:13 AM, Junio C Hamano wrote:

"Derrick Stolee via GitGitGadget" [off-list ref] writes:

quoted

@@ -3143,6 +3144,9 @@ int prepare_revision_walk(struct rev_info *revs)
  		commit_list_sort_by_date(&revs->commits);
  	if (revs->no_walk)
  		return 0;
+	if (revs->limited &&
+	    git_env_bool(GIT_TEST_COMMIT_GRAPH, 0))
+		revs->limited = 0;
  	if (revs->limited) {
  		if (limit_list(revs) < 0)
  			return -1;

That is equivalent to say

	if (git_env_bool(GIT_TEST_COMMIT_GRAPH, 0))
		revs->limited = 0;

Not exactly equivalent, because we can use short-circuiting to avoid the 
git_env_bool check, but I see what you mean.

Wouldn't that make the codepath that involves limit_list()
completely unreachable while testing, though?

Testing with GIT_TEST_COMMIT_GRAPH=0 would still hit limit_list(). Both 
modes are important to test (for instance, to ensure we still have 
correct behavior without a commit-graph file).

The title only mentions "topo-order" logic, but the topo-order is
not the only reason why limited bit can be set, is it?  When showing
merges, simplifying merges, or post-processing to show ancestry
path, or showing a bottom-limited revision range, the limited bit is
automatically set because all of these depend on first calling
limit_list() and then postprocessing its result.  Doesn't it hurt
these cases to unconditionally drop limited bit?

You're right that we only want to do this in the topo-order case, so 
perhaps the diff should instead be:

  	if (revs->no_walk)
  		return 0;
+	if (revs->topo_order &&
+	    git_env_bool(GIT_TEST_COMMIT_GRAPH, 0))
+		revs->limited = 0;
  	if (revs->limited) {
  		if (limit_list(revs) < 0)
  			return -1;

Thanks,
-Stolee