Documentation: asciidoc formatting fix for git-cvsexportcommit doc.
[git/gitweb.git] / update-ref.c
blob65dc3d6385756a11aac257a3ed6a9dfcb68cce53
1 #include "cache.h"
2 #include "refs.h"
4 static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
6 static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
8 char buf[40];
9 int fd = open(path, O_RDONLY), nr;
10 if (fd < 0)
11 return -1;
12 nr = read(fd, buf, 40);
13 close(fd);
14 if (nr != 40 || get_sha1_hex(buf, currsha1) < 0)
15 return -1;
16 return memcmp(oldsha1, currsha1, 20) ? -1 : 0;
19 int main(int argc, char **argv)
21 char *hex;
22 const char *refname, *value, *oldval, *path, *lockpath;
23 unsigned char sha1[20], oldsha1[20], currsha1[20];
24 int fd, written;
26 setup_git_directory();
27 if (argc < 3 || argc > 4)
28 usage(git_update_ref_usage);
30 refname = argv[1];
31 value = argv[2];
32 oldval = argv[3];
33 if (get_sha1(value, sha1) < 0)
34 die("%s: not a valid SHA1", value);
35 memset(oldsha1, 0, 20);
36 if (oldval && get_sha1(oldval, oldsha1) < 0)
37 die("%s: not a valid old SHA1", oldval);
39 path = resolve_ref(git_path("%s", refname), currsha1, !!oldval);
40 if (!path)
41 die("No such ref: %s", refname);
43 if (oldval) {
44 if (memcmp(currsha1, oldsha1, 20))
45 die("Ref %s changed to %s", refname, sha1_to_hex(currsha1));
46 /* Nothing to do? */
47 if (!memcmp(oldsha1, sha1, 20))
48 exit(0);
50 path = strdup(path);
51 lockpath = mkpath("%s.lock", path);
53 fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
54 if (fd < 0)
55 die("Unable to create %s", lockpath);
56 hex = sha1_to_hex(sha1);
57 hex[40] = '\n';
58 written = write(fd, hex, 41);
59 close(fd);
60 if (written != 41) {
61 unlink(lockpath);
62 die("Unable to write to %s", lockpath);
66 * Re-read the ref after getting the lock to verify
68 if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
69 unlink(lockpath);
70 die("Ref lock failed");
74 * Finally, replace the old ref with the new one
76 if (rename(lockpath, path) < 0) {
77 unlink(lockpath);
78 die("Unable to create %s", path);
80 return 0;