object-name: abbreviate loose object names without disambiguate_state

The function `find_short_object_filename()` takes an object ID and
computes the minimum required object name length to make it unique. This
is done by reusing the object disambiguation infrastructure, where we
iterate through every loose object and then update the disambiguate
state one by one.

Ultimately, we don't care about the disambiguate state though. It is
used because this infrastructure knows how to enumerate only those
objects that match a given prefix. But now that we have extended the
`odb_for_each_object()` function to do this for us we have an easier way
to do this. Consequently, we really only use the disambiguate state now
to propagate `struct min_abbrev_data`.

Refactor the code and drop this indirection so that we use `struct
min_abbrev_data` directly. This also allows us to drop some now-unused
logic from the disambiguate infrastructure.

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

Author: pks-t

object-name.c

@@ -48,7 +48,6 @@ struct disambiguate_state {
 	unsigned candidate_ok:1;
 	unsigned disambiguate_fn_used:1;
 	unsigned ambiguous:1;
-	unsigned always_call_fn:1;
 };
 
 static int update_disambiguate_state(const struct object_id *current,
@@ -58,10 +57,6 @@ static int update_disambiguate_state(const struct object_id *current,
 	struct disambiguate_state *ds = cb_data;
 
 	/* The hash algorithm of current has already been filtered */
-	if (ds->always_call_fn) {
-		ds->ambiguous = ds->fn(ds->repo, current, ds->cb_data) ? 1 : 0;
-		return ds->ambiguous;
-	}
 	if (!ds->candidate_exists) {
 		/* this is the first candidate */
 		oidcpy(&ds->candidate, current);
@@ -107,19 +102,6 @@ static int update_disambiguate_state(const struct object_id *current,
 	return 0;
 }
 
-static void find_short_object_filename(struct disambiguate_state *ds)
-{
-	struct odb_for_each_object_options opts = {
-		.prefix = &ds->bin_pfx,
-		.prefix_hex_len = ds->len,
-	};
-	struct odb_source *source;
-
-	for (source = ds->repo->objects->sources; source && !ds->ambiguous; source = source->next)
-		odb_source_loose_for_each_object(source, NULL, update_disambiguate_state,
-						 ds, &opts);
-}
-
 static int finish_object_disambiguation(struct disambiguate_state *ds,
 					struct object_id *oid)
 {
@@ -632,11 +614,26 @@ static int extend_abbrev_len(const struct object_id *oid,
 	return 0;
 }
 
-static int repo_extend_abbrev_len(struct repository *r UNUSED,
-				  const struct object_id *oid,
-				  void *cb_data)
+static int extend_abbrev_len_loose(const struct object_id *oid,
+				   struct object_info *oi UNUSED,
+				   void *cb_data)
 {
-	return extend_abbrev_len(oid, cb_data);
+	struct min_abbrev_data *data = cb_data;
+	extend_abbrev_len(oid, data);
+	return 0;
+}
+
+static void find_abbrev_len_loose(struct min_abbrev_data *mad)
+{
+	struct odb_for_each_object_options opts = {
+		.prefix = mad->oid,
+		.prefix_hex_len = mad->cur_len,
+	};
+	struct odb_source *source;
+
+	for (source = mad->repo->objects->sources; source; source = source->next)
+		odb_source_loose_for_each_object(source, NULL, extend_abbrev_len_loose,
+						 mad, &opts);
 }
 
 static void find_abbrev_len_for_midx(struct multi_pack_index *m,
@@ -752,9 +749,7 @@ int repo_find_unique_abbrev_r(struct repository *r, char *hex,
 {
 	const struct git_hash_algo *algo =
 		oid->algo ? &hash_algos[oid->algo] : r->hash_algo;
-	struct disambiguate_state ds;
 	struct min_abbrev_data mad;
-	struct object_id oid_ret;
 	const unsigned hexsz = algo->hexsz;
 
 	if (len < 0) {
@@ -794,16 +789,7 @@ int repo_find_unique_abbrev_r(struct repository *r, char *hex,
 	mad.oid = oid;
 
 	find_abbrev_len_packed(&mad);
-
-	if (init_object_disambiguation(r, hex, mad.cur_len, algo, &ds) < 0)
-		return -1;
-
-	ds.fn = repo_extend_abbrev_len;
-	ds.always_call_fn = 1;
-	ds.cb_data = (void *)&mad;
-
-	find_short_object_filename(&ds);
-	(void)finish_object_disambiguation(&ds, &oid_ret);
+	find_abbrev_len_loose(&mad);
 
 	hex[mad.cur_len] = 0;
 	return mad.cur_len;