Andrew's git - gitweb.git/blob

   1#include "cache.h"
   2#include "refs.h"
   3
   4static const char git_update_ref_usage[] = "git-update-ref <refname> <value> [<oldval>]";
   5
   6static int re_verify(const char *path, unsigned char *oldsha1, unsigned char *currsha1)
   7{
   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;
  17}
  18
  19int main(int argc, char **argv)
  20{
  21        char *hex;
  22        const char *refname, *value, *oldval, *path;
  23        char *lockpath;
  24        unsigned char sha1[20], oldsha1[20], currsha1[20];
  25        int fd, written;
  26
  27        setup_git_directory();
  28        if (argc < 3 || argc > 4)
  29                usage(git_update_ref_usage);
  30
  31        refname = argv[1];
  32        value = argv[2];
  33        oldval = argv[3];
  34        if (get_sha1(value, sha1) < 0)
  35                die("%s: not a valid SHA1", value);
  36        memset(oldsha1, 0, 20);
  37        if (oldval && get_sha1(oldval, oldsha1) < 0)
  38                die("%s: not a valid old SHA1", oldval);
  39
  40        path = resolve_ref(git_path("%s", refname), currsha1, !!oldval);
  41        if (!path)
  42                die("No such ref: %s", refname);
  43
  44        if (oldval) {
  45                if (memcmp(currsha1, oldsha1, 20))
  46                        die("Ref %s is at %s but expected %s", refname, sha1_to_hex(currsha1), sha1_to_hex(oldsha1));
  47                /* Nothing to do? */
  48                if (!memcmp(oldsha1, sha1, 20))
  49                        exit(0);
  50        }
  51        path = strdup(path);
  52        lockpath = mkpath("%s.lock", path);
  53        if (safe_create_leading_directories(lockpath) < 0)
  54                die("Unable to create all of %s", lockpath);
  55
  56        fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
  57        if (fd < 0)
  58                die("Unable to create %s", lockpath);
  59        hex = sha1_to_hex(sha1);
  60        hex[40] = '\n';
  61        written = write(fd, hex, 41);
  62        close(fd);
  63        if (written != 41) {
  64                unlink(lockpath);
  65                die("Unable to write to %s", lockpath);
  66        }
  67
  68        /*
  69         * Re-read the ref after getting the lock to verify
  70         */
  71        if (oldval && re_verify(path, oldsha1, currsha1) < 0) {
  72                unlink(lockpath);
  73                die("Ref lock failed");
  74        }
  75
  76        /*
  77         * Finally, replace the old ref with the new one
  78         */
  79        if (rename(lockpath, path) < 0) {
  80                unlink(lockpath);
  81                die("Unable to create %s", path);
  82        }
  83        return 0;
  84}