5 static const char git_update_ref_usage
[] = "git-update-ref <refname> <value> [<oldval>]";
9 static const char *resolve_ref(const char *path
, unsigned char *sha1
)
11 int depth
= MAXDEPTH
, len
;
22 /* Special case: non-existing file */
23 if (lstat(path
, &st
) < 0) {
30 /* Follow "normalized" - ie "refs/.." symlinks by hand */
31 if (S_ISLNK(st
.st_mode
)) {
32 len
= readlink(path
, buffer
, sizeof(buffer
)-1);
33 if (len
>= 5 && !memcmp("refs/", buffer
, 5)) {
34 path
= git_path("%.*s", len
, buffer
);
40 * Anything else, just open it and try to use it as
43 fd
= open(path
, O_RDONLY
);
46 len
= read(fd
, buffer
, sizeof(buffer
)-1);
50 * Is it a symbolic ref?
52 if (len
< 4 || memcmp("ref:", buffer
, 4))
56 while (len
&& isspace(*buf
))
58 while (len
&& isspace(buf
[len
-1]))
60 path
= git_path("%.*s", len
, buf
);
62 if (len
< 40 || get_sha1_hex(buffer
, sha1
))
67 static int re_verify(const char *path
, unsigned char *oldsha1
, unsigned char *currsha1
)
70 int fd
= open(path
, O_RDONLY
), nr
;
73 nr
= read(fd
, buf
, 40);
75 if (nr
!= 40 || get_sha1_hex(buf
, currsha1
) < 0)
77 return memcmp(oldsha1
, currsha1
, 20) ? -1 : 0;
80 int main(int argc
, char **argv
)
83 const char *refname
, *value
, *oldval
, *path
, *lockpath
;
84 unsigned char sha1
[20], oldsha1
[20], currsha1
[20];
87 setup_git_directory();
88 if (argc
< 3 || argc
> 4)
89 usage(git_update_ref_usage
);
94 if (get_sha1(value
, sha1
) < 0)
95 die("%s: not a valid SHA1", value
);
96 memset(oldsha1
, 0, 20);
97 if (oldval
&& get_sha1(oldval
, oldsha1
) < 0)
98 die("%s: not a valid old SHA1", oldval
);
100 path
= resolve_ref(git_path("%s", refname
), currsha1
);
102 die("No such ref: %s", refname
);
105 if (memcmp(currsha1
, oldsha1
, 20))
106 die("Ref %s changed to %s", refname
, sha1_to_hex(currsha1
));
108 if (!memcmp(oldsha1
, sha1
, 20))
112 lockpath
= mkpath("%s.lock", path
);
114 fd
= open(lockpath
, O_CREAT
| O_EXCL
| O_WRONLY
, 0666);
116 die("Unable to create %s", lockpath
);
117 hex
= sha1_to_hex(sha1
);
119 written
= write(fd
, hex
, 41);
123 die("Unable to write to %s", lockpath
);
127 * Re-read the ref after getting the lock to verify
129 if (oldval
&& re_verify(path
, oldsha1
, currsha1
) < 0) {
131 die("Ref lock failed");
135 * Finally, replace the old ref with the new one
137 if (rename(lockpath
, path
) < 0) {
139 die("Unable to create %s", path
);