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#include "cache.h"
#include "refs.h"
#include <ctype.h>
static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
#define MAXDEPTH 5
const char *resolve_ref(const char *path, unsigned char *sha1)
{
int depth = MAXDEPTH, len;
char buffer[256];
for (;;) {
struct stat st;
int fd;
if (--depth < 0)
return NULL;
/* Special case: non-existing file */
if (lstat(path, &st) < 0) {
if (errno != ENOENT)
return NULL;
memset(sha1, 0, 20);
return path;
}
/* Follow "normalized" - ie "refs/.." symlinks by hand */
if (S_ISLNK(st.st_mode)) {
len = readlink(path, buffer, sizeof(buffer)-1);
if (len >= 5 && !memcmp("refs/", buffer, 5)) {
path = git_path("%.*s", len, buffer);
continue;
}
}
/*
* Anything else, just open it and try to use it as
* a ref
*/
fd = open(path, O_RDONLY);
if (fd < 0)
return NULL;
len = read(fd, buffer, sizeof(buffer)-1);
close(fd);
break;
}
if (len < 40 || get_sha1_hex(buffer, sha1))
return NULL;
return path;
}
static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
{
char buf[40];
int fd = open(path, O_RDONLY), nr;
if (fd < 0)
return -1;
nr = read(fd, buf, 40);
close(fd);
if (nr != 40 || get_sha1_hex(buf, currsha1) < 0)
return -1;
return memcmp(oldsha1, currsha1, 20) ? -1 : 0;
}
int main(int argc, char **argv)
{
char *hex;
const char *refname, *value, *oldval, *path, *lockpath;
unsigned char sha1[20], oldsha1[20], currsha1[20];
int fd, written;
setup_git_directory();
if (argc < 3 || argc > 4)
usage(git_update_ref_usage);
refname = argv[1];
value = argv[2];
oldval = argv[3];
if (get_sha1(value, sha1) < 0)
die("%s: not a valid SHA1", value);
memset(oldsha1, 0, 20);
if (oldval && get_sha1(oldval, oldsha1) < 0)
die("%s: not a valid old SHA1", oldval);
path = resolve_ref(git_path("%s", refname), currsha1);
if (!path)
die("No such ref: %s", refname);
if (oldval) {
if (memcmp(currsha1, oldsha1, 20))
die("Ref %s changed to %s", refname, sha1_to_hex(currsha1));
/* Nothing to do? */
if (!memcmp(oldsha1, sha1, 20))
exit(0);
}
path = strdup(path);
lockpath = mkpath("%s.lock", path);
fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
if (fd < 0)
die("Unable to create %s", lockpath);
hex = sha1_to_hex(sha1);
hex[40] = '\n';
written = write(fd, hex, 41);
close(fd);
if (written != 41) {
unlink(lockpath);
die("Unable to write to %s", lockpath);
}
/*
* Re-read the ref after getting the lock to verify
*/
if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
unlink(lockpath);
die("Ref lock failed");
}
/*
* Finally, replace the old ref with the new one
*/
if (rename(lockpath, path) < 0) {
unlink(lockpath);
die("Unable to create %s", path);
}
return 0;
}
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