object-names: support input of oids in any supported hash

Support short oids encoded in any algorithm, while ensuring enough of
the oid is specified to disambiguate between all of the oids in the
repository encoded in any algorithm.

By default have the code continue to only accept oids specified in the
storage hash algorithm of the repository, but when something is
ambiguous display all of the possible oids from any accepted oid
encoding.

A new flag is added GET_OID_HASH_ANY that when supplied causes the
code to accept oids specified in any hash algorithm, and to return the
oids that were resolved.

This implements the functionality that allows both SHA-1 and SHA-256
object names, from the "Object names on the command line" section of
the hash function transition document.

Care is taken in get_short_oid so that when the result is ambiguous
the output remains the same if GIT_OID_HASH_ANY was not supplied.  If
GET_OID_HASH_ANY was supplied objects of any hash algorithm that match
the prefix are displayed.

This required updating repo_for_each_abbrev to give it a parameter so
that it knows to look at all hash algorithms.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/rev-parse.c

@@ -882,7 +882,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				continue;
 			}
 			if (skip_prefix(arg, "--disambiguate=", &arg)) {
-				repo_for_each_abbrev(the_repository, arg,
+				repo_for_each_abbrev(the_repository, arg, the_hash_algo,
 						     show_abbrev, NULL);
 				continue;
 			}

hash-ll.h

@@ -145,6 +145,7 @@ struct object_id {
 #define GET_OID_RECORD_PATH     0200
 #define GET_OID_ONLY_TO_DIE    04000
 #define GET_OID_REQUIRE_PATH  010000
+#define GET_OID_HASH_ANY      020000
 
 #define GET_OID_DISAMBIGUATORS \
 	(GET_OID_COMMIT | GET_OID_COMMITTISH | \

object-name.c

@@ -25,6 +25,7 @@
 #include "midx.h"
 #include "commit-reach.h"
 #include "date.h"
+#include "object-file-convert.h"
 
 static int get_oid_oneline(struct repository *r, const char *, struct object_id *, struct commit_list *);
 
@@ -49,6 +50,7 @@ struct disambiguate_state {
 
 static void update_candidates(struct disambiguate_state *ds, const struct object_id *current)
 {
+	/* 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;
@@ -134,6 +136,8 @@ static void unique_in_midx(struct multi_pack_index *m,
 {
 	uint32_t num, i, first = 0;
 	const struct object_id *current = NULL;
+	int len = ds->len > ds->repo->hash_algo->hexsz ?
+		ds->repo->hash_algo->hexsz : ds->len;
 	num = m->num_objects;
 
 	if (!num)
@@ -149,7 +153,7 @@ static void unique_in_midx(struct multi_pack_index *m,
 	for (i = first; i < num && !ds->ambiguous; i++) {
 		struct object_id oid;
 		current = nth_midxed_object_oid(&oid, m, i);
-		if (!match_hash(ds->len, ds->bin_pfx.hash, current->hash))
+		if (!match_hash(len, ds->bin_pfx.hash, current->hash))
 			break;
 		update_candidates(ds, current);
 	}
@@ -159,6 +163,8 @@ static void unique_in_pack(struct packed_git *p,
 			   struct disambiguate_state *ds)
 {
 	uint32_t num, i, first = 0;
+	int len = ds->len > ds->repo->hash_algo->hexsz ?
+		ds->repo->hash_algo->hexsz : ds->len;
 
 	if (p->multi_pack_index)
 		return;
@@ -177,7 +183,7 @@ static void unique_in_pack(struct packed_git *p,
 	for (i = first; i < num && !ds->ambiguous; i++) {
 		struct object_id oid;
 		nth_packed_object_id(&oid, p, i);
-		if (!match_hash(ds->len, ds->bin_pfx.hash, oid.hash))
+		if (!match_hash(len, ds->bin_pfx.hash, oid.hash))
 			break;
 		update_candidates(ds, &oid);
 	}
@@ -188,6 +194,10 @@ static void find_short_packed_object(struct disambiguate_state *ds)
 	struct multi_pack_index *m;
 	struct packed_git *p;
 
+	/* Skip, unless oids from the storage hash algorithm are wanted */
+	if (ds->bin_pfx.algo && (&hash_algos[ds->bin_pfx.algo] != ds->repo->hash_algo))
+		return;
+
 	for (m = get_multi_pack_index(ds->repo); m && !ds->ambiguous;
 	     m = m->next)
 		unique_in_midx(m, ds);
@@ -326,11 +336,12 @@ int set_disambiguate_hint_config(const char *var, const char *value)
 
 static int init_object_disambiguation(struct repository *r,
 				      const char *name, int len,
+				      const struct git_hash_algo *algo,
 				      struct disambiguate_state *ds)
 {
 	int i;
 
-	if (len < MINIMUM_ABBREV || len > the_hash_algo->hexsz)
+	if (len < MINIMUM_ABBREV || len > GIT_MAX_HEXSZ)
 		return -1;
 
 	memset(ds, 0, sizeof(*ds));
@@ -357,6 +368,7 @@ static int init_object_disambiguation(struct repository *r,
 	ds->len = len;
 	ds->hex_pfx[len] = '\0';
 	ds->repo = r;
+	ds->bin_pfx.algo = algo ? hash_algo_by_ptr(algo) : GIT_HASH_UNKNOWN;
 	prepare_alt_odb(r);
 	return 0;
 }
@@ -491,9 +503,10 @@ static int repo_collect_ambiguous(struct repository *r UNUSED,
 	return collect_ambiguous(oid, data);
 }
 
-static int sort_ambiguous(const void *a, const void *b, void *ctx)
+static int sort_ambiguous(const void *va, const void *vb, void *ctx)
 {
 	struct repository *sort_ambiguous_repo = ctx;
+	const struct object_id *a = va, *b = vb;
 	int a_type = oid_object_info(sort_ambiguous_repo, a, NULL);
 	int b_type = oid_object_info(sort_ambiguous_repo, b, NULL);
 	int a_type_sort;
@@ -503,8 +516,12 @@ static int sort_ambiguous(const void *a, const void *b, void *ctx)
 	 * Sorts by hash within the same object type, just as
 	 * oid_array_for_each_unique() would do.
 	 */
-	if (a_type == b_type)
-		return oidcmp(a, b);
+	if (a_type == b_type) {
+		if (a->algo == b->algo)
+			return oidcmp(a, b);
+		else
+			return a->algo > b->algo ? 1 : -1;
+	}
 
 	/*
 	 * Between object types show tags, then commits, and finally
@@ -533,8 +550,12 @@ static enum get_oid_result get_short_oid(struct repository *r,
 	int status;
 	struct disambiguate_state ds;
 	int quietly = !!(flags & GET_OID_QUIETLY);
+	const struct git_hash_algo *algo = r->hash_algo;
 
-	if (init_object_disambiguation(r, name, len, &ds) < 0)
+	if (flags & GET_OID_HASH_ANY)
+		algo = NULL;
+
+	if (init_object_disambiguation(r, name, len, algo, &ds) < 0)
 		return -1;
 
 	if (HAS_MULTI_BITS(flags & GET_OID_DISAMBIGUATORS))
@@ -588,7 +609,7 @@ static enum get_oid_result get_short_oid(struct repository *r,
 		if (!ds.ambiguous)
 			ds.fn = NULL;
 
-		repo_for_each_abbrev(r, ds.hex_pfx, collect_ambiguous, &collect);
+		repo_for_each_abbrev(r, ds.hex_pfx, algo, collect_ambiguous, &collect);
 		sort_ambiguous_oid_array(r, &collect);
 
 		if (oid_array_for_each(&collect, show_ambiguous_object, &out))
@@ -610,13 +631,14 @@ static enum get_oid_result get_short_oid(struct repository *r,
 }
 
 int repo_for_each_abbrev(struct repository *r, const char *prefix,
+			 const struct git_hash_algo *algo,
 			 each_abbrev_fn fn, void *cb_data)
 {
 	struct oid_array collect = OID_ARRAY_INIT;
 	struct disambiguate_state ds;
 	int ret;
 
-	if (init_object_disambiguation(r, prefix, strlen(prefix), &ds) < 0)
+	if (init_object_disambiguation(r, prefix, strlen(prefix), algo, &ds) < 0)
 		return -1;
 
 	ds.always_call_fn = 1;
@@ -787,10 +809,12 @@ void strbuf_add_unique_abbrev(struct strbuf *sb, const struct object_id *oid,
 int repo_find_unique_abbrev_r(struct repository *r, char *hex,
 			      const struct object_id *oid, int len)
 {
+	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 = r->hash_algo->hexsz;
+	const unsigned hexsz = algo->hexsz;
 
 	if (len < 0) {
 		unsigned long count = repo_approximate_object_count(r);
@@ -826,7 +850,7 @@ int repo_find_unique_abbrev_r(struct repository *r, char *hex,
 
 	find_abbrev_len_packed(&mad);
 
-	if (init_object_disambiguation(r, hex, mad.cur_len, &ds) < 0)
+	if (init_object_disambiguation(r, hex, mad.cur_len, algo, &ds) < 0)
 		return -1;
 
 	ds.fn = repo_extend_abbrev_len;

object-name.h

@@ -67,7 +67,8 @@ enum get_oid_result get_oid_with_context(struct repository *repo, const char *st
 
 
 typedef int each_abbrev_fn(const struct object_id *oid, void *);
-int repo_for_each_abbrev(struct repository *r, const char *prefix, each_abbrev_fn, void *);
+int repo_for_each_abbrev(struct repository *r, const char *prefix,
+			 const struct git_hash_algo *algo, each_abbrev_fn, void *);
 
 int set_disambiguate_hint_config(const char *var, const char *value);