files-backend: make reflog iterator go through per-worktree reflog

refs/bisect is unfortunately per-worktree, so we need to look in
per-worktree logs/refs/bisect in addition to per-repo logs/refs. The
current iterator only goes through per-repo logs/refs.

Use merge iterator to walk two ref stores at the same time and pick
per-worktree refs from the right iterator.

PS. Note the unsorted order of for_each_reflog in the test. This is
supposed to be OK, for now. If we enforce order on for_each_reflog()
then some more work will be required.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs/files-backend.c

@@ -106,15 +106,6 @@ static void files_reflog_path(struct files_ref_store *refs,
 			      struct strbuf *sb,
 			      const char *refname)
 {
-	if (!refname) {
-		/*
-		 * FIXME: of course this is wrong in multi worktree
-		 * setting. To be fixed real soon.
-		 */
-		strbuf_addf(sb, "%s/logs", refs->gitcommondir);
-		return;
-	}
-
 	switch (ref_type(refname)) {
 	case REF_TYPE_PER_WORKTREE:
 	case REF_TYPE_PSEUDOREF:
@@ -2055,23 +2046,63 @@ static struct ref_iterator_vtable files_reflog_iterator_vtable = {
 	files_reflog_iterator_abort
 };
 
-static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
+static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
+						  const char *gitdir)
 {
-	struct files_ref_store *refs =
-		files_downcast(ref_store, REF_STORE_READ,
-			       "reflog_iterator_begin");
 	struct files_reflog_iterator *iter = xcalloc(1, sizeof(*iter));
 	struct ref_iterator *ref_iterator = &iter->base;
 	struct strbuf sb = STRBUF_INIT;
 
 	base_ref_iterator_init(ref_iterator, &files_reflog_iterator_vtable);
-	files_reflog_path(refs, &sb, NULL);
+	strbuf_addf(&sb, "%s/logs", gitdir);
 	iter->dir_iterator = dir_iterator_begin(sb.buf);
 	iter->ref_store = ref_store;
 	strbuf_release(&sb);
+
 	return ref_iterator;
 }
 
+static enum iterator_selection reflog_iterator_select(
+	struct ref_iterator *iter_worktree,
+	struct ref_iterator *iter_common,
+	void *cb_data)
+{
+	if (iter_worktree) {
+		/*
+		 * We're a bit loose here. We probably should ignore
+		 * common refs if they are accidentally added as
+		 * per-worktree refs.
+		 */
+		return ITER_SELECT_0;
+	} else if (iter_common) {
+		if (ref_type(iter_common->refname) == REF_TYPE_NORMAL)
+			return ITER_SELECT_1;
+
+		/*
+		 * The main ref store may contain main worktree's
+		 * per-worktree refs, which should be ignored
+		 */
+		return ITER_SKIP_1;
+	} else
+		return ITER_DONE;
+}
+
+static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_store)
+{
+	struct files_ref_store *refs =
+		files_downcast(ref_store, REF_STORE_READ,
+			       "reflog_iterator_begin");
+
+	if (!strcmp(refs->gitdir, refs->gitcommondir)) {
+		return reflog_iterator_begin(ref_store, refs->gitcommondir);
+	} else {
+		return merge_ref_iterator_begin(
+			reflog_iterator_begin(ref_store, refs->gitdir),
+			reflog_iterator_begin(ref_store, refs->gitcommondir),
+			reflog_iterator_select, refs);
+	}
+}
+
 /*
  * If update is a direct update of head_ref (the reference pointed to
  * by HEAD), then add an extra REF_LOG_ONLY update for HEAD.

t/t1407-worktree-ref-store.sh

@@ -49,4 +49,34 @@ test_expect_success 'create_symref(FOO, refs/heads/master)' '
 	test_cmp expected actual
 '
 
+test_expect_success 'for_each_reflog()' '
+	echo $_z40 > .git/logs/PSEUDO-MAIN &&
+	mkdir -p     .git/logs/refs/bisect &&
+	echo $_z40 > .git/logs/refs/bisect/random &&
+
+	echo $_z40 > .git/worktrees/wt/logs/PSEUDO-WT &&
+	mkdir -p     .git/worktrees/wt/logs/refs/bisect &&
+	echo $_z40 > .git/worktrees/wt/logs/refs/bisect/wt-random &&
+
+	$RWT for-each-reflog | cut -c 42- | sort >actual &&
+	cat >expected <<-\EOF &&
+	HEAD 0x1
+	PSEUDO-WT 0x0
+	refs/bisect/wt-random 0x0
+	refs/heads/master 0x0
+	refs/heads/wt-master 0x0
+	EOF
+	test_cmp expected actual &&
+
+	$RMAIN for-each-reflog | cut -c 42- | sort >actual &&
+	cat >expected <<-\EOF &&
+	HEAD 0x1
+	PSEUDO-MAIN 0x0
+	refs/bisect/random 0x0
+	refs/heads/master 0x0
+	refs/heads/wt-master 0x0
+	EOF
+	test_cmp expected actual
+'
+
 test_done