object-name: move logic to compute loose abbreviation length

The function `repo_find_unique_abbrev_r()` takes as input an object ID
as well as a minimum object ID length and returns the minimum required
prefix to make the object ID unique.

The logic that computes the abbreviation length for loose objects is
deeply tied to the loose object storage format. As such, it would fail
in case a different object storage format was used.

Prepare for making this logic generic to the backend by moving the logic
into a new `odb_source_loose_find_abbrev_len()` function that is part of
"object-file.c".

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/object-file.c b/object-file.c
index 13732f324f..4f77ce0982 100644
--- a/object-file.c
+++ b/object-file.c
@@ -1952,6 +1952,44 @@ out:
 	return ret;
 }
 
+struct find_abbrev_len_data {
+	const struct object_id *oid;
+	unsigned len;
+};
+
+static int find_abbrev_len_cb(const struct object_id *oid,
+			      struct object_info *oi UNUSED,
+			      void *cb_data)
+{
+	struct find_abbrev_len_data *data = cb_data;
+	unsigned len = oid_common_prefix_hexlen(oid, data->oid);
+	if (len != hash_algos[oid->algo].hexsz && len >= data->len)
+		data->len = len + 1;
+	return 0;
+}
+
+int odb_source_loose_find_abbrev_len(struct odb_source *source,
+				     const struct object_id *oid,
+				     unsigned min_len,
+				     unsigned *out)
+{
+	struct odb_for_each_object_options opts = {
+		.prefix = oid,
+		.prefix_hex_len = min_len,
+	};
+	struct find_abbrev_len_data data = {
+		.oid = oid,
+		.len = min_len,
+	};
+	int ret;
+
+	ret = odb_source_loose_for_each_object(source, NULL, find_abbrev_len_cb,
+					       &data, &opts);
+	*out = data.len;
+
+	return ret;
+}
+
 static int append_loose_object(const struct object_id *oid,
 			       const char *path UNUSED,
 			       void *data)