refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5
   6 /* We allow "recursive" symbolic refs. Only within reason, though */
   7 #define MAXDEPTH 5
   8
   9 #ifndef USE_SYMLINK_HEAD
  10 #define USE_SYMLINK_HEAD 1
  11 #endif
  12
  13 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  14 {
  15         int depth = MAXDEPTH, len;
  16         char buffer[256];
  17
  18         for (;;) {
  19                 struct stat st;
  20                 char *buf;
  21                 int fd;
  22
  23                 if (--depth < 0)
  24                         return NULL;
  25
  26                 /* Special case: non-existing file.
  27                  * Not having the refs/heads/new-branch is OK
  28                  * if we are writing into it, so is .git/HEAD
  29                  * that points at refs/heads/master still to be
  30                  * born.  It is NOT OK if we are resolving for
  31                  * reading.
  32                  */
  33                 if (lstat(path, &st) < 0) {
  34                         if (reading || errno != ENOENT)
  35                                 return NULL;
  36                         memset(sha1, 0, 20);
  37                         return path;
  38                 }
  39
  40                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  41                 if (S_ISLNK(st.st_mode)) {
  42                         len = readlink(path, buffer, sizeof(buffer)-1);
  43                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  44                                 path = git_path("%.*s", len, buffer);
  45                                 continue;
  46                         }
  47                 }
  48
  49                 /*
  50                  * Anything else, just open it and try to use it as
  51                  * a ref
  52                  */
  53                 fd = open(path, O_RDONLY);
  54                 if (fd < 0)
  55                         return NULL;
  56                 len = read(fd, buffer, sizeof(buffer)-1);
  57                 close(fd);
  58
  59                 /*
  60                  * Is it a symbolic ref?
  61                  */
  62                 if (len < 4 || memcmp("ref:", buffer, 4))
  63                         break;
  64                 buf = buffer + 4;
  65                 len -= 4;
  66                 while (len && isspace(*buf))
  67                         buf++, len--;
  68                 while (len && isspace(buf[len-1]))
  69                         buf[--len] = 0;
  70                 path = git_path("%.*s", len, buf);
  71         }
  72         if (len < 40 || get_sha1_hex(buffer, sha1))
  73                 return NULL;
  74         return path;
  75 }
  76
  77 int create_symref(const char *git_HEAD, const char *refs_heads_master)
  78 {
  79         const char *lockpath;
  80         char ref[1000];
  81         int fd, len, written;
  82
  83 #if USE_SYMLINK_HEAD
  84         if (!only_use_symrefs) {
  85                 unlink(git_HEAD);
  86                 if (!symlink(refs_heads_master, git_HEAD))
  87                         return 0;
  88                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
  89         }
  90 #endif
  91
  92         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
  93         if (sizeof(ref) <= len) {
  94                 error("refname too long: %s", refs_heads_master);
  95                 return -1;
  96         }
  97         lockpath = mkpath("%s.lock", git_HEAD);
  98         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
  99         written = write(fd, ref, len);
 100         close(fd);
 101         if (written != len) {
 102                 unlink(lockpath);
 103                 error("Unable to write to %s", lockpath);
 104                 return -2;
 105         }
 106         if (rename(lockpath, git_HEAD) < 0) {
 107                 unlink(lockpath);
 108                 error("Unable to create %s", git_HEAD);
 109                 return -3;
 110         }
 111         return 0;
 112 }
 113
 114 int read_ref(const char *filename, unsigned char *sha1)
 115 {
 116         if (resolve_ref(filename, sha1, 1))
 117                 return 0;
 118         return -1;
 119 }
 120
 121 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 122 {
 123         int retval = 0;
 124         DIR *dir = opendir(git_path("%s", base));
 125
 126         if (dir) {
 127                 struct dirent *de;
 128                 int baselen = strlen(base);
 129                 char *path = xmalloc(baselen + 257);
 130
 131                 if (!strncmp(base, "./", 2)) {
 132                         base += 2;
 133                         baselen -= 2;
 134                 }
 135                 memcpy(path, base, baselen);
 136                 if (baselen && base[baselen-1] != '/')
 137                         path[baselen++] = '/';
 138
 139                 while ((de = readdir(dir)) != NULL) {
 140                         unsigned char sha1[20];
 141                         struct stat st;
 142                         int namelen;
 143
 144                         if (de->d_name[0] == '.')
 145                                 continue;
 146                         namelen = strlen(de->d_name);
 147                         if (namelen > 255)
 148                                 continue;
 149                         memcpy(path + baselen, de->d_name, namelen+1);
 150                         if (stat(git_path("%s", path), &st) < 0)
 151                                 continue;
 152                         if (S_ISDIR(st.st_mode)) {
 153                                 retval = do_for_each_ref(path, fn);
 154                                 if (retval)
 155                                         break;
 156                                 continue;
 157                         }
 158                         if (read_ref(git_path("%s", path), sha1) < 0)
 159                                 continue;
 160                         if (!has_sha1_file(sha1))
 161                                 continue;
 162                         retval = fn(path, sha1);
 163                         if (retval)
 164                                 break;
 165                 }
 166                 free(path);
 167                 closedir(dir);
 168         }
 169         return retval;
 170 }
 171
 172 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 173 {
 174         unsigned char sha1[20];
 175         if (!read_ref(git_path("HEAD"), sha1))
 176                 return fn("HEAD", sha1);
 177         return 0;
 178 }
 179
 180 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 181 {
 182         return do_for_each_ref("refs", fn);
 183 }
 184
 185 static char *ref_file_name(const char *ref)
 186 {
 187         char *base = get_refs_directory();
 188         int baselen = strlen(base);
 189         int reflen = strlen(ref);
 190         char *ret = xmalloc(baselen + 2 + reflen);
 191         sprintf(ret, "%s/%s", base, ref);
 192         return ret;
 193 }
 194
 195 static char *ref_lock_file_name(const char *ref)
 196 {
 197         char *base = get_refs_directory();
 198         int baselen = strlen(base);
 199         int reflen = strlen(ref);
 200         char *ret = xmalloc(baselen + 7 + reflen);
 201         sprintf(ret, "%s/%s.lock", base, ref);
 202         return ret;
 203 }
 204
 205 int get_ref_sha1(const char *ref, unsigned char *sha1)
 206 {
 207         const char *filename;
 208
 209         if (check_ref_format(ref))
 210                 return -1;
 211         filename = git_path("refs/%s", ref);
 212         return read_ref(filename, sha1);
 213 }
 214
 215 static int lock_ref_file(const char *filename, const char *lock_filename,
 216                          const unsigned char *old_sha1)
 217 {
 218         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 219         unsigned char current_sha1[20];
 220         int retval;
 221         if (fd < 0) {
 222                 return error("Couldn't open lock file for %s: %s",
 223                              filename, strerror(errno));
 224         }
 225         retval = read_ref(filename, current_sha1);
 226         if (old_sha1) {
 227                 if (retval) {
 228                         close(fd);
 229                         unlink(lock_filename);
 230                         return error("Could not read the current value of %s",
 231                                      filename);
 232                 }
 233                 if (memcmp(current_sha1, old_sha1, 20)) {
 234                         close(fd);
 235                         unlink(lock_filename);
 236                         error("The current value of %s is %s",
 237                               filename, sha1_to_hex(current_sha1));
 238                         return error("Expected %s",
 239                                      sha1_to_hex(old_sha1));
 240                 }
 241         } else {
 242                 if (!retval) {
 243                         close(fd);
 244                         unlink(lock_filename);
 245                         return error("Unexpectedly found a value of %s for %s",
 246                                      sha1_to_hex(current_sha1), filename);
 247                 }
 248         }
 249         return fd;
 250 }
 251
 252 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 253 {
 254         char *filename;
 255         char *lock_filename;
 256         int retval;
 257         if (check_ref_format(ref))
 258                 return -1;
 259         filename = ref_file_name(ref);
 260         lock_filename = ref_lock_file_name(ref);
 261         retval = lock_ref_file(filename, lock_filename, old_sha1);
 262         free(filename);
 263         free(lock_filename);
 264         return retval;
 265 }
 266
 267 static int write_ref_file(const char *filename,
 268                           const char *lock_filename, int fd,
 269                           const unsigned char *sha1)
 270 {
 271         char *hex = sha1_to_hex(sha1);
 272         char term = '\n';
 273         if (write(fd, hex, 40) < 40 ||
 274             write(fd, &term, 1) < 1) {
 275                 error("Couldn't write %s\n", filename);
 276                 close(fd);
 277                 return -1;
 278         }
 279         close(fd);
 280         rename(lock_filename, filename);
 281         return 0;
 282 }
 283
 284 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 285 {
 286         char *filename;
 287         char *lock_filename;
 288         int retval;
 289         if (fd < 0)
 290                 return -1;
 291         if (check_ref_format(ref))
 292                 return -1;
 293         filename = ref_file_name(ref);
 294         lock_filename = ref_lock_file_name(ref);
 295         retval = write_ref_file(filename, lock_filename, fd, sha1);
 296         free(filename);
 297         free(lock_filename);
 298         return retval;
 299 }
 300
 301 /*
 302  * Make sure "ref" is something reasonable to have under ".git/refs/";
 303  * We do not like it if:
 304  *
 305  * - any path component of it begins with ".", or
 306  * - it has double dots "..", or
 307  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 308  * - it ends with a "/".
 309  */
 310
 311 static inline int bad_ref_char(int ch)
 312 {
 313         return (((unsigned) ch) <= ' ' ||
 314                 ch == '~' || ch == '^' || ch == ':');
 315 }
 316
 317 int check_ref_format(const char *ref)
 318 {
 319         int ch, level;
 320         const char *cp = ref;
 321
 322         level = 0;
 323         while (1) {
 324                 while ((ch = *cp++) == '/')
 325                         ; /* tolerate duplicated slashes */
 326                 if (!ch)
 327                         return -1; /* should not end with slashes */
 328
 329                 /* we are at the beginning of the path component */
 330                 if (ch == '.' || bad_ref_char(ch))
 331                         return -1;
 332
 333                 /* scan the rest of the path component */
 334                 while ((ch = *cp++) != 0) {
 335                         if (bad_ref_char(ch))
 336                                 return -1;
 337                         if (ch == '/')
 338                                 break;
 339                         if (ch == '.' && *cp == '.')
 340                                 return -1;
 341                 }
 342                 level++;
 343                 if (!ch) {
 344                         if (level < 2)
 345                                 return -1; /* at least of form "heads/blah" */
 346                         return 0;
 347                 }
 348         }
 349 }
 350
 351 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 352 {
 353         char *filename;
 354         char *lock_filename;
 355         int fd;
 356         int retval;
 357         if (check_ref_format(ref))
 358                 return -1;
 359         filename = ref_file_name(ref);
 360         lock_filename = ref_lock_file_name(ref);
 361         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 362         if (fd < 0) {
 363                 error("Writing %s", lock_filename);
 364                 perror("Open");
 365         }
 366         retval = write_ref_file(filename, lock_filename, fd, sha1);
 367         free(filename);
 368         free(lock_filename);
 369         return retval;
 370 }