refs/files: sort merged worktree and common reflogs

When iterating through reflogs in a worktree we create a merged iterator
that merges reflogs from both refdbs. The resulting refs are ordered so
that instead we first return all worktree reflogs before we return all
common refs.

This is the only remaining case where a ref iterator returns entries in
a non-lexicographic order. The result would look something like the
following (listed with a command we introduce in a subsequent commit):

```
$ git reflog list
HEAD
refs/worktree/per-worktree
refs/heads/main
refs/heads/wt
```

So we first print the per-worktree reflogs in lexicographic order, then
the common reflogs in lexicographic order. This is confusing and not
consistent with how we print per-worktree refs, which are exclusively
sorted lexicographically.

Sort reflogs lexicographically in the same way as we sort normal refs.
As this is already implemented properly by the "reftable" backend via a
separate selection function, we simply pull out that logic and reuse it
for the "files" backend. As logs are properly sorted now, mark the
merged reflog iterator as sorted.

Tests will be added in a subsequent commit.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

refs/files-backend.c

@@ -2210,32 +2210,6 @@ static struct ref_iterator *reflog_iterator_begin(struct ref_store *ref_store,
 	return ref_iterator;
 }
 
-static enum iterator_selection reflog_iterator_select(
-	struct ref_iterator *iter_worktree,
-	struct ref_iterator *iter_common,
-	void *cb_data UNUSED)
-{
-	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 (parse_worktree_ref(iter_common->refname, NULL, NULL,
-				       NULL) == REF_WORKTREE_SHARED)
-			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 =
@@ -2246,9 +2220,9 @@ static struct ref_iterator *files_reflog_iterator_begin(struct ref_store *ref_st
 		return reflog_iterator_begin(ref_store, refs->gitcommondir);
 	} else {
 		return merge_ref_iterator_begin(
-			0, reflog_iterator_begin(ref_store, refs->base.gitdir),
+			1, reflog_iterator_begin(ref_store, refs->base.gitdir),
 			reflog_iterator_begin(ref_store, refs->gitcommondir),
-			reflog_iterator_select, refs);
+			ref_iterator_select, refs);
 	}
 }
 

refs/iterator.c

@@ -98,6 +98,49 @@ struct merge_ref_iterator {
 	struct ref_iterator **current;
 };
 
+enum iterator_selection ref_iterator_select(struct ref_iterator *iter_worktree,
+					    struct ref_iterator *iter_common,
+					    void *cb_data UNUSED)
+{
+	if (iter_worktree && !iter_common) {
+		/*
+		 * Return the worktree ref if there are no more common refs.
+		 */
+		return ITER_SELECT_0;
+	} else if (iter_common) {
+		/*
+		 * In case we have pending worktree and common refs we need to
+		 * yield them based on their lexicographical order. Worktree
+		 * refs that have the same name as common refs shadow the
+		 * latter.
+		 */
+		if (iter_worktree) {
+			int cmp = strcmp(iter_worktree->refname,
+					 iter_common->refname);
+			if (cmp < 0)
+				return ITER_SELECT_0;
+			else if (!cmp)
+				return ITER_SELECT_0_SKIP_1;
+		}
+
+		 /*
+		  * We now know that the lexicographically-next ref is a common
+		  * ref. When the common ref is a shared one we return it.
+		  */
+		if (parse_worktree_ref(iter_common->refname, NULL, NULL,
+				       NULL) == REF_WORKTREE_SHARED)
+			return ITER_SELECT_1;
+
+		/*
+		 * Otherwise, if the common ref is a per-worktree ref we skip
+		 * it because it would belong to the main worktree, not ours.
+		 */
+		return ITER_SKIP_1;
+	} else {
+		return ITER_DONE;
+	}
+}
+
 static int merge_ref_iterator_advance(struct ref_iterator *ref_iterator)
 {
 	struct merge_ref_iterator *iter =

refs/refs-internal.h

@@ -386,6 +386,15 @@ typedef enum iterator_selection ref_iterator_select_fn(
 		struct ref_iterator *iter0, struct ref_iterator *iter1,
 		void *cb_data);
 
+/*
+ * An implementation of ref_iterator_select_fn that merges worktree and common
+ * refs. Per-worktree refs from the common iterator are ignored, worktree refs
+ * override common refs. Refs are selected lexicographically.
+ */
+enum iterator_selection ref_iterator_select(struct ref_iterator *iter_worktree,
+					    struct ref_iterator *iter_common,
+					    void *cb_data);
+
 /*
  * Iterate over the entries from iter0 and iter1, with the values
  * interleaved as directed by the select function. The iterator takes

refs/reftable-backend.c

@@ -504,49 +504,6 @@ static struct reftable_ref_iterator *ref_iterator_for_stack(struct reftable_ref_
 	return iter;
 }
 
-static enum iterator_selection iterator_select(struct ref_iterator *iter_worktree,
-					       struct ref_iterator *iter_common,
-					       void *cb_data UNUSED)
-{
-	if (iter_worktree && !iter_common) {
-		/*
-		 * Return the worktree ref if there are no more common refs.
-		 */
-		return ITER_SELECT_0;
-	} else if (iter_common) {
-		/*
-		 * In case we have pending worktree and common refs we need to
-		 * yield them based on their lexicographical order. Worktree
-		 * refs that have the same name as common refs shadow the
-		 * latter.
-		 */
-		if (iter_worktree) {
-			int cmp = strcmp(iter_worktree->refname,
-					 iter_common->refname);
-			if (cmp < 0)
-				return ITER_SELECT_0;
-			else if (!cmp)
-				return ITER_SELECT_0_SKIP_1;
-		}
-
-		 /*
-		  * We now know that the lexicographically-next ref is a common
-		  * ref. When the common ref is a shared one we return it.
-		  */
-		if (parse_worktree_ref(iter_common->refname, NULL, NULL,
-				       NULL) == REF_WORKTREE_SHARED)
-			return ITER_SELECT_1;
-
-		/*
-		 * Otherwise, if the common ref is a per-worktree ref we skip
-		 * it because it would belong to the main worktree, not ours.
-		 */
-		return ITER_SKIP_1;
-	} else {
-		return ITER_DONE;
-	}
-}
-
 static struct ref_iterator *reftable_be_iterator_begin(struct ref_store *ref_store,
 						       const char *prefix,
 						       const char **exclude_patterns,
@@ -576,7 +533,7 @@ static struct ref_iterator *reftable_be_iterator_begin(struct ref_store *ref_sto
 	 */
 	worktree_iter = ref_iterator_for_stack(refs, refs->worktree_stack, prefix, flags);
 	return merge_ref_iterator_begin(1, &worktree_iter->base, &main_iter->base,
-					iterator_select, NULL);
+					ref_iterator_select, NULL);
 }
 
 static int reftable_be_read_raw_ref(struct ref_store *ref_store,
@@ -1759,7 +1716,7 @@ static struct ref_iterator *reftable_be_reflog_iterator_begin(struct ref_store *
 	worktree_iter = reflog_iterator_for_stack(refs, refs->worktree_stack);
 
 	return merge_ref_iterator_begin(1, &worktree_iter->base, &main_iter->base,
-					iterator_select, NULL);
+					ref_iterator_select, NULL);
 }
 
 static int yield_log_record(struct reftable_log_record *log,