Skip to content

Commit 6809557

Browse files
chriscoolgitster
chriscool
authored and
gitster
committed
replace_object: add mechanism to replace objects found in "refs/replace/"
The code implementing this mechanism has been copied more-or-less from the commit graft code. This mechanism is used in "read_sha1_file". sha1 passed to this function that match a ref name in "refs/replace/" are replaced by the sha1 that has been read in the ref. We "die" if the replacement recursion depth is too high or if we can't read the replacement object. Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 2926870 commit 6809557

File tree

4 files changed

+125
-3
lines changed

4 files changed

+125
-3
lines changed

‎Makefile‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -512,6 +512,7 @@ LIB_OBJS += read-cache.o
512512
LIB_OBJS += reflog-walk.o
513513
LIB_OBJS += refs.o
514514
LIB_OBJS += remote.o
515+
LIB_OBJS += replace_object.o
515516
LIB_OBJS += rerere.o
516517
LIB_OBJS += revision.o
517518
LIB_OBJS += run-command.o

‎commit.h‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -124,6 +124,8 @@ struct commit_graft *read_graft_line(char *buf, int len);
124124
int register_commit_graft(struct commit_graft *, int);
125125
struct commit_graft *lookup_commit_graft(const unsigned char *sha1);
126126

127+
const unsigned char *lookup_replace_object(const unsigned char *sha1);
128+
127129
extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2, int cleanup);
128130
extern struct commit_list *get_merge_bases_many(struct commit *one, int n, struct commit **twos, int cleanup);
129131
extern struct commit_list *get_octopus_merge_bases(struct commit_list *in);

‎replace_object.c‎

Lines changed: 111 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,111 @@
1+
#include "cache.h"
2+
#include "sha1-lookup.h"
3+
#include "refs.h"
4+
5+
static struct replace_object {
6+
unsigned char sha1[2][20];
7+
} **replace_object;
8+
9+
static int replace_object_alloc, replace_object_nr;
10+
11+
static const unsigned char *replace_sha1_access(size_t index, void *table)
12+
{
13+
struct replace_object **replace = table;
14+
return replace[index]->sha1[0];
15+
}
16+
17+
static int replace_object_pos(const unsigned char *sha1)
18+
{
19+
return sha1_pos(sha1, replace_object, replace_object_nr,
20+
replace_sha1_access);
21+
}
22+
23+
static int register_replace_object(struct replace_object *replace,
24+
int ignore_dups)
25+
{
26+
int pos = replace_object_pos(replace->sha1[0]);
27+
28+
if (0 <= pos) {
29+
if (ignore_dups)
30+
free(replace);
31+
else {
32+
free(replace_object[pos]);
33+
replace_object[pos] = replace;
34+
}
35+
return 1;
36+
}
37+
pos = -pos - 1;
38+
if (replace_object_alloc <= ++replace_object_nr) {
39+
replace_object_alloc = alloc_nr(replace_object_alloc);
40+
replace_object = xrealloc(replace_object,
41+
sizeof(*replace_object) *
42+
replace_object_alloc);
43+
}
44+
if (pos < replace_object_nr)
45+
memmove(replace_object + pos + 1,
46+
replace_object + pos,
47+
(replace_object_nr - pos - 1) *
48+
sizeof(*replace_object));
49+
replace_object[pos] = replace;
50+
return 0;
51+
}
52+
53+
static int register_replace_ref(const char *refname,
54+
const unsigned char *sha1,
55+
int flag, void *cb_data)
56+
{
57+
/* Get sha1 from refname */
58+
const char *slash = strrchr(refname, '/');
59+
const char *hash = slash ? slash + 1 : refname;
60+
struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
61+
62+
if (strlen(hash) != 40 || get_sha1_hex(hash, repl_obj->sha1[0])) {
63+
free(repl_obj);
64+
warning("bad replace ref name: %s", refname);
65+
return 0;
66+
}
67+
68+
/* Copy sha1 from the read ref */
69+
hashcpy(repl_obj->sha1[1], sha1);
70+
71+
/* Register new object */
72+
if (register_replace_object(repl_obj, 1))
73+
die("duplicate replace ref: %s", refname);
74+
75+
return 0;
76+
}
77+
78+
static void prepare_replace_object(void)
79+
{
80+
static int replace_object_prepared;
81+
82+
if (replace_object_prepared)
83+
return;
84+
85+
for_each_replace_ref(register_replace_ref, NULL);
86+
replace_object_prepared = 1;
87+
}
88+
89+
/* We allow "recursive" replacement. Only within reason, though */
90+
#define MAXREPLACEDEPTH 5
91+
92+
const unsigned char *lookup_replace_object(const unsigned char *sha1)
93+
{
94+
int pos, depth = MAXREPLACEDEPTH;
95+
const unsigned char *cur = sha1;
96+
97+
prepare_replace_object();
98+
99+
/* Try to recursively replace the object */
100+
do {
101+
if (--depth < 0)
102+
die("replace depth too high for object %s",
103+
sha1_to_hex(sha1));
104+
105+
pos = replace_object_pos(cur);
106+
if (0 <= pos)
107+
cur = replace_object[pos]->sha1[1];
108+
} while (0 <= pos);
109+
110+
return cur;
111+
}

‎sha1_file.c‎

Lines changed: 11 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2148,10 +2148,18 @@ static void *read_object(const unsigned char *sha1, enum object_type *type,
21482148
void *read_sha1_file(const unsigned char *sha1, enum object_type *type,
21492149
unsigned long *size)
21502150
{
2151-
void *data = read_object(sha1, type, size);
2151+
const unsigned char *repl = lookup_replace_object(sha1);
2152+
void *data = read_object(repl, type, size);
2153+
2154+
/* die if we replaced an object with one that does not exist */
2155+
if (!data && repl != sha1)
2156+
die("replacement %s not found for %s",
2157+
sha1_to_hex(repl), sha1_to_hex(sha1));
2158+
21522159
/* legacy behavior is to die on corrupted objects */
2153-
if (!data && (has_loose_object(sha1) || has_packed_and_bad(sha1)))
2154-
die("object %s is corrupted", sha1_to_hex(sha1));
2160+
if (!data && (has_loose_object(repl) || has_packed_and_bad(repl)))
2161+
die("object %s is corrupted", sha1_to_hex(repl));
2162+
21552163
return data;
21562164
}
21572165

0 commit comments

Comments
 (0)