thodg/libgit2

diff --git a/src/attr.c b/src/attr.c
index 553c071..e6e274e 100644
--- a/src/attr.c
+++ b/src/attr.c
@@ -193,7 +193,7 @@ int git_attr_foreach(
 
 				error = callback(assign->name, assign->value, payload);
 				if (error) {
-					GITERR_CALLBACK(error);
+					giterr_set_after_callback(error);
 					goto cleanup;
 				}
 			}
diff --git a/src/checkout.c b/src/checkout.c
index 4c64252..a292e3d 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -123,10 +123,13 @@ static int checkout_notify(
 		path = delta->old_file.path;
 	}
 
-	return giterr_set_callback(
-		data->opts.notify_cb(
-			why, path, baseline, target, workdir, data->opts.notify_payload),
-		"git_checkout notification");
+	{
+		int error = data->opts.notify_cb(
+			why, path, baseline, target, workdir, data->opts.notify_payload);
+
+		return giterr_set_after_callback_function(
+			error, "git_checkout notification");
+	}
 }
 
 static bool checkout_is_workdir_modified(
diff --git a/src/common.h b/src/common.h
index 71182bb..e315b59 100644
--- a/src/common.h
+++ b/src/common.h
@@ -83,7 +83,8 @@ int giterr_set_regex(const regex_t *regex, int error_code);
  *
  * @return This always returns the `error_code` parameter.
  */
-GIT_INLINE(int) giterr_set_callback(int error_code, const char *action)
+GIT_INLINE(int) giterr_set_after_callback_function(
+	int error_code, const char *action)
 {
 	if (error_code) {
 		const git_error *e = giterr_last();
@@ -95,9 +96,11 @@ GIT_INLINE(int) giterr_set_callback(int error_code, const char *action)
 }
 
 #ifdef GIT_WIN32
-#define GITERR_CALLBACK(code) giterr_set_callback((code), __FUNCTION__)
+#define giterr_set_after_callback(code) \
+	giterr_set_after_callback_function((code), __FUNCTION__)
 #else
-#define GITERR_CALLBACK(code) giterr_set_callback((code), __func__)
+#define giterr_set_after_callback(code) \
+	giterr_set_after_callback_function((code), __func__)
 #endif
 
 /**
diff --git a/src/config.c b/src/config.c
index 5477b04..056a6ae 100644
--- a/src/config.c
+++ b/src/config.c
@@ -508,7 +508,7 @@ int git_config_backend_foreach_match(
 
 		/* abort iterator on non-zero return value */
 		if ((error = cb(entry, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
@@ -536,7 +536,7 @@ int git_config_foreach_match(
 
 	while (!(error = git_config_next(&entry, iter))) {
 		if ((error = cb(entry, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
@@ -799,7 +799,7 @@ int git_config_get_multivar_foreach(
 		found = 1;
 
 		if ((err = cb(entry, payload)) != 0) {
-			GITERR_CALLBACK(err);
+			giterr_set_after_callback(err);
 			break;
 		}
 	}
diff --git a/src/diff.c b/src/diff.c
index b7657e4..83adc2a 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -60,7 +60,11 @@ static int diff_insert_delta(
 
 		if (error) {
 			git__free(delta);
-			return (error > 0) ? 0 : giterr_set_callback(error, "git_diff");
+
+			if (error > 0)	/* positive value means to skip this delta */
+				return 0;
+			else			/* negative value means to cancel diff */
+				return giterr_set_after_callback_function(error, "git_diff");
 		}
 	}
 
@@ -1389,7 +1393,7 @@ int git_diff__paired_foreach(
 		}
 
 		if ((error = cb(h2i, i2w, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/diff_patch.c b/src/diff_patch.c
index 11f0247..9c2eb88 100644
--- a/src/diff_patch.c
+++ b/src/diff_patch.c
@@ -202,7 +202,7 @@ static int diff_patch_invoke_file_callback(
 	if (!output->file_cb)
 		return 0;
 
-	return giterr_set_callback(
+	return giterr_set_after_callback_function(
 		output->file_cb(patch->delta, progress, output->payload),
 		"git_patch");
 }
diff --git a/src/diff_print.c b/src/diff_print.c
index ff477e4..7a70e2b 100644
--- a/src/diff_print.c
+++ b/src/diff_print.c
@@ -398,7 +398,7 @@ int git_diff_print(
 			diff, print_file, print_hunk, print_line, &pi);
 
 		if (error) /* make sure error message is set */
-			giterr_set_callback(error, "git_diff_print");
+			giterr_set_after_callback_function(error, "git_diff_print");
 	}
 
 	git_buf_free(&buf);
@@ -427,7 +427,7 @@ int git_patch_print(
 			diff_print_patch_line, &pi);
 
 		if (error) /* make sure error message is set */
-			giterr_set_callback(error, "git_patch_print");
+			giterr_set_after_callback_function(error, "git_patch_print");
 	}
 
 	git_buf_free(&temp);
diff --git a/src/fetchhead.c b/src/fetchhead.c
index 2f217fa..4435454 100644
--- a/src/fetchhead.c
+++ b/src/fetchhead.c
@@ -271,7 +271,7 @@ int git_repository_fetchhead_foreach(git_repository *repo,
 
 		error = cb(ref_name, remote_url, &oid, is_merge, payload);
 		if (error) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			goto done;
 		}
 	}
diff --git a/src/index.c b/src/index.c
index 671bdfa..bb81f66 100644
--- a/src/index.c
+++ b/src/index.c
@@ -2117,7 +2117,7 @@ int git_index_add_all(
 			if (error > 0) /* return > 0 means skip this one */
 				continue;
 			if (error < 0) { /* return < 0 means abort */
-				GITERR_CALLBACK(error);
+				giterr_set_after_callback(error);
 				break;
 			}
 		}
@@ -2204,10 +2204,8 @@ static int index_apply_to_all(
 				error = 0;
 				continue;
 			}
-			if (error < 0) { /* return < 0 means abort */
-				giterr_set_callback(error, "git_index_matched_path");
+			if (error < 0)   /* return < 0 means abort */
 				break;
-			}
 		}
 
 		/* index manipulation may alter entry, so don't depend on it */
@@ -2252,8 +2250,13 @@ int git_index_remove_all(
 	git_index_matched_path_cb cb,
 	void *payload)
 {
-	return index_apply_to_all(
+	int error = index_apply_to_all(
 		index, INDEX_ACTION_REMOVE, pathspec, cb, payload);
+
+	if (error) /* make sure error is set if callback stopped iteration */
+		giterr_set_after_callback(error);
+
+	return error;
 }
 
 int git_index_update_all(
@@ -2262,6 +2265,11 @@ int git_index_update_all(
 	git_index_matched_path_cb cb,
 	void *payload)
 {
-	return index_apply_to_all(
+	int error = index_apply_to_all(
 		index, INDEX_ACTION_UPDATE, pathspec, cb, payload);
+
+	if (error) /* make sure error is set if callback stopped iteration */
+		giterr_set_after_callback(error);
+
+	return error;
 }
diff --git a/src/indexer.c b/src/indexer.c
index 320845b..88897d0 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -387,7 +387,7 @@ on_error:
 static int do_progress_callback(git_indexer *idx, git_transfer_progress *stats)
 {
 	if (idx->progress_cb)
-		return giterr_set_callback(
+		return giterr_set_after_callback_function(
 			idx->progress_cb(stats, idx->progress_payload),
 			"indexer progress");
 	return 0;
diff --git a/src/merge.c b/src/merge.c
index f1778c9..5640be5 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -288,7 +288,7 @@ int git_repository_mergehead_foreach(
 			goto cleanup;
 
 		if ((error = cb(&oid, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			goto cleanup;
 		}
 
diff --git a/src/notes.c b/src/notes.c
index e0d5ad1..7959049 100644
--- a/src/notes.c
+++ b/src/notes.c
@@ -584,7 +584,7 @@ int git_note_foreach(
 
 	while (!(error = git_note_next(&note_id, &annotated_id, iter))) {
 		if ((error = note_cb(&note_id, &annotated_id, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/odb_loose.c b/src/odb_loose.c
index 78cd792..fd4ffff 100644
--- a/src/odb_loose.c
+++ b/src/odb_loose.c
@@ -733,7 +733,7 @@ static int foreach_object_dir_cb(void *_state, git_buf *path)
 	if (filename_to_oid(&oid, path->ptr + state->dir_len) < 0)
 		return 0;
 
-	return giterr_set_callback(
+	return giterr_set_after_callback_function(
 		state->cb(&oid, state->data), "git_odb_foreach");
 }
 
diff --git a/src/pack-objects.c b/src/pack-objects.c
index 09b7248..7ce1b6c 100644
--- a/src/pack-objects.c
+++ b/src/pack-objects.c
@@ -234,7 +234,7 @@ int git_packbuilder_insert(git_packbuilder *pb, const git_oid *oid,
 				pb->nr_objects, 0, pb->progress_cb_payload);
 
 			if (ret)
-				return GITERR_CALLBACK(ret);
+				return giterr_set_after_callback(ret);
 		}
 	}
 
diff --git a/src/pack.c b/src/pack.c
index fd53ef4..23fcf35 100644
--- a/src/pack.c
+++ b/src/pack.c
@@ -1088,10 +1088,8 @@ int git_pack_foreach_entry(
 	}
 
 	for (i = 0; i < p->num_objects; i++)
-		if ((error = cb(p->oids[i], data)) != 0) {
-			GITERR_CALLBACK(error);
-			break;
-		}
+		if ((error = cb(p->oids[i], data)) != 0)
+			return giterr_set_after_callback(error);
 
 	return error;
 }
diff --git a/src/path.c b/src/path.c
index 8c19e00..365bd6c 100644
--- a/src/path.c
+++ b/src/path.c
@@ -438,7 +438,7 @@ int git_path_walk_up(
 		iter.ptr[scan] = oldc;
 
 		if (error) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 
@@ -882,7 +882,7 @@ int git_path_direach(
 		git_buf_truncate(path, wd_len); /* restore path */
 
 		if (error != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/push.c b/src/push.c
index 8ebba15..adba880 100644
--- a/src/push.c
+++ b/src/push.c
@@ -661,7 +661,7 @@ int git_push_status_foreach(git_push *push,
 	git_vector_foreach(&push->status, i, status) {
 		int error = cb(status->ref, status->msg, data);
 		if (error)
-			return GITERR_CALLBACK(error);
+			return giterr_set_after_callback(error);
 	}
 
 	return 0;
diff --git a/src/refs.c b/src/refs.c
index 25037cc..4f3a557 100644
--- a/src/refs.c
+++ b/src/refs.c
@@ -518,7 +518,7 @@ int git_reference_foreach(
 
 	while (!(error = git_reference_next(&ref, iter))) {
 		if ((error = callback(ref, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
@@ -544,7 +544,7 @@ int git_reference_foreach_name(
 
 	while (!(error = git_reference_next_name(&refname, iter))) {
 		if ((error = callback(refname, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
@@ -571,7 +571,7 @@ int git_reference_foreach_glob(
 
 	while (!(error = git_reference_next_name(&refname, iter))) {
 		if ((error = callback(refname, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/remote.c b/src/remote.c
index d46364a..689de23 100644
--- a/src/remote.c
+++ b/src/remote.c
@@ -1349,7 +1349,7 @@ static int rename_fetch_refspecs(
 			strcmp(git_buf_cstr(&base), spec->string)) {
 
 			if ((error = callback(spec->string, payload)) != 0) {
-				GITERR_CALLBACK(error);
+				giterr_set_after_callback(error);
 				break;
 			}
 
diff --git a/src/stash.c b/src/stash.c
index fb5bb2e..eae5696 100644
--- a/src/stash.c
+++ b/src/stash.c
@@ -588,7 +588,7 @@ int git_stash_foreach(
 			payload);
 
 		if (error) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/status.c b/src/status.c
index d4a4362..9bde8fb 100644
--- a/src/status.c
+++ b/src/status.c
@@ -393,7 +393,7 @@ int git_status_foreach_ext(
 			status_entry->index_to_workdir->old_file.path;
 
 		if ((error = cb(path, status_entry->status, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	}
diff --git a/src/submodule.c b/src/submodule.c
index 5298302..1c36d36 100644
--- a/src/submodule.c
+++ b/src/submodule.c
@@ -169,7 +169,7 @@ int git_submodule_foreach(
 		}
 
 		if ((error = callback(sm, sm->name, payload)) != 0) {
-			GITERR_CALLBACK(error);
+			giterr_set_after_callback(error);
 			break;
 		}
 	});
diff --git a/src/tag.c b/src/tag.c
index adf2819..be56b05 100644
--- a/src/tag.c
+++ b/src/tag.c
@@ -426,8 +426,8 @@ static int tags_cb(const char *ref, void *data)
 		return 0; /* no tag */
 
 	if (!(error = git_reference_name_to_id(&oid, d->repo, ref))) {
-		error = d->cb(ref, &oid, d->cb_data);
-		giterr_set_callback(error, "git_tag_foreach");
+		if ((error = d->cb(ref, &oid, d->cb_data)) != 0)
+			giterr_set_after_callback_function(error, "git_tag_foreach");
 	}
 
 	return error;
diff --git a/src/tree.c b/src/tree.c
index 5f35ac3..4d77ff7 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -883,9 +883,12 @@ static int tree_walk(
 
 	git_vector_foreach(&tree->entries, i, entry) {
 		if (preorder) {
-			if ((error = callback(path->ptr, entry, payload)) < 0)
-				return giterr_set_callback(error, "git_tree_walk");
-			if (error > 0) {
+			error = callback(path->ptr, entry, payload);
+			if (error < 0) { /* negative value stops iteration */
+				giterr_set_after_callback_function(error, "git_tree_walk");
+				break;
+			}
+			if (error > 0) { /* positive value skips this entry */
 				error = 0;
 				continue;
 			}
@@ -916,8 +919,11 @@ static int tree_walk(
 		}
 
 		if (!preorder) {
-			if ((error = callback(path->ptr, entry, payload)) < 0)
-				return giterr_set_callback(error, "git_tree_walk");
+			error = callback(path->ptr, entry, payload);
+			if (error < 0) { /* negative value stops iteration */
+				giterr_set_after_callback_function(error, "git_tree_walk");
+				break;
+			}
 			error = 0;
 		}
 	}