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 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  10 {
  11         int depth = MAXDEPTH, len;
  12         char buffer[256];
  13
  14         for (;;) {
  15                 struct stat st;
  16                 char *buf;
  17                 int fd;
  18
  19                 if (--depth < 0)
  20                         return NULL;
  21
  22                 /* Special case: non-existing file.
  23                  * Not having the refs/heads/new-branch is OK
  24                  * if we are writing into it, so is .git/HEAD
  25                  * that points at refs/heads/master still to be
  26                  * born.  It is NOT OK if we are resolving for
  27                  * reading.
  28                  */
  29                 if (lstat(path, &st) < 0) {
  30                         if (reading || errno != ENOENT)
  31                                 return NULL;
  32                         memset(sha1, 0, 20);
  33                         return path;
  34                 }
  35
  36                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  37                 if (S_ISLNK(st.st_mode)) {
  38                         len = readlink(path, buffer, sizeof(buffer)-1);
  39                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  40                                 path = git_path("%.*s", len, buffer);
  41                                 continue;
  42                         }
  43                 }
  44
  45                 /*
  46                  * Anything else, just open it and try to use it as
  47                  * a ref
  48                  */
  49                 fd = open(path, O_RDONLY);
  50                 if (fd < 0)
  51                         return NULL;
  52                 len = read(fd, buffer, sizeof(buffer)-1);
  53                 close(fd);
  54
  55                 /*
  56                  * Is it a symbolic ref?
  57                  */
  58                 if (len < 4 || memcmp("ref:", buffer, 4))
  59                         break;
  60                 buf = buffer + 4;
  61                 len -= 4;
  62                 while (len && isspace(*buf))
  63                         buf++, len--;
  64                 while (len && isspace(buf[len-1]))
  65                         buf[--len] = 0;
  66                 path = git_path("%.*s", len, buf);
  67         }
  68         if (len < 40 || get_sha1_hex(buffer, sha1))
  69                 return NULL;
  70         return path;
  71 }
  72
  73 int create_symref(const char *git_HEAD, const char *refs_heads_master)
  74 {
  75         const char *lockpath;
  76         char ref[1000];
  77         int fd, len, written;
  78
  79 #ifdef USE_SYMLINK_HEAD
  80         if (!only_use_symrefs) {
  81                 unlink(git_HEAD);
  82                 if (!symlink(refs_heads_master, git_HEAD))
  83                         return 0;
  84                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
  85         }
  86 #endif
  87
  88         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
  89         if (sizeof(ref) <= len) {
  90                 error("refname too long: %s", refs_heads_master);
  91                 return -1;
  92         }
  93         lockpath = mkpath("%s.lock", git_HEAD);
  94         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
  95         written = write(fd, ref, len);
  96         close(fd);
  97         if (written != len) {
  98                 unlink(lockpath);
  99                 error("Unable to write to %s", lockpath);
 100                 return -2;
 101         }
 102         if (rename(lockpath, git_HEAD) < 0) {
 103                 unlink(lockpath);
 104                 error("Unable to create %s", git_HEAD);
 105                 return -3;
 106         }
 107         return 0;
 108 }
 109
 110 int read_ref(const char *filename, unsigned char *sha1)
 111 {
 112         if (resolve_ref(filename, sha1, 1))
 113                 return 0;
 114         return -1;
 115 }
 116
 117 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 118 {
 119         int retval = 0;
 120         DIR *dir = opendir(git_path("%s", base));
 121
 122         if (dir) {
 123                 struct dirent *de;
 124                 int baselen = strlen(base);
 125                 char *path = xmalloc(baselen + 257);
 126
 127                 if (!strncmp(base, "./", 2)) {
 128                         base += 2;
 129                         baselen -= 2;
 130                 }
 131                 memcpy(path, base, baselen);
 132                 if (baselen && base[baselen-1] != '/')
 133                         path[baselen++] = '/';
 134
 135                 while ((de = readdir(dir)) != NULL) {
 136                         unsigned char sha1[20];
 137                         struct stat st;
 138                         int namelen;
 139
 140                         if (de->d_name[0] == '.')
 141                                 continue;
 142                         namelen = strlen(de->d_name);
 143                         if (namelen > 255)
 144                                 continue;
 145                         memcpy(path + baselen, de->d_name, namelen+1);
 146                         if (stat(git_path("%s", path), &st) < 0)
 147                                 continue;
 148                         if (S_ISDIR(st.st_mode)) {
 149                                 retval = do_for_each_ref(path, fn);
 150                                 if (retval)
 151                                         break;
 152                                 continue;
 153                         }
 154                         if (read_ref(git_path("%s", path), sha1) < 0)
 155                                 continue;
 156                         if (!has_sha1_file(sha1))
 157                                 continue;
 158                         retval = fn(path, sha1);
 159                         if (retval)
 160                                 break;
 161                 }
 162                 free(path);
 163                 closedir(dir);
 164         }
 165         return retval;
 166 }
 167
 168 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 169 {
 170         unsigned char sha1[20];
 171         if (!read_ref(git_path("HEAD"), sha1))
 172                 return fn("HEAD", sha1);
 173         return 0;
 174 }
 175
 176 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 177 {
 178         return do_for_each_ref("refs", fn);
 179 }
 180
 181 static char *ref_file_name(const char *ref)
 182 {
 183         char *base = get_refs_directory();
 184         int baselen = strlen(base);
 185         int reflen = strlen(ref);
 186         char *ret = xmalloc(baselen + 2 + reflen);
 187         sprintf(ret, "%s/%s", base, ref);
 188         return ret;
 189 }
 190
 191 static char *ref_lock_file_name(const char *ref)
 192 {
 193         char *base = get_refs_directory();
 194         int baselen = strlen(base);
 195         int reflen = strlen(ref);
 196         char *ret = xmalloc(baselen + 7 + reflen);
 197         sprintf(ret, "%s/%s.lock", base, ref);
 198         return ret;
 199 }
 200
 201 int get_ref_sha1(const char *ref, unsigned char *sha1)
 202 {
 203         const char *filename;
 204
 205         if (check_ref_format(ref))
 206                 return -1;
 207         filename = git_path("refs/%s", ref);
 208         return read_ref(filename, sha1);
 209 }
 210
 211 static int lock_ref_file(const char *filename, const char *lock_filename,
 212                          const unsigned char *old_sha1)
 213 {
 214         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 215         unsigned char current_sha1[20];
 216         int retval;
 217         if (fd < 0) {
 218                 return error("Couldn't open lock file for %s: %s",
 219                              filename, strerror(errno));
 220         }
 221         retval = read_ref(filename, current_sha1);
 222         if (old_sha1) {
 223                 if (retval) {
 224                         close(fd);
 225                         unlink(lock_filename);
 226                         return error("Could not read the current value of %s",
 227                                      filename);
 228                 }
 229                 if (memcmp(current_sha1, old_sha1, 20)) {
 230                         close(fd);
 231                         unlink(lock_filename);
 232                         error("The current value of %s is %s",
 233                               filename, sha1_to_hex(current_sha1));
 234                         return error("Expected %s",
 235                                      sha1_to_hex(old_sha1));
 236                 }
 237         } else {
 238                 if (!retval) {
 239                         close(fd);
 240                         unlink(lock_filename);
 241                         return error("Unexpectedly found a value of %s for %s",
 242                                      sha1_to_hex(current_sha1), filename);
 243                 }
 244         }
 245         return fd;
 246 }
 247
 248 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 249 {
 250         char *filename;
 251         char *lock_filename;
 252         int retval;
 253         if (check_ref_format(ref))
 254                 return -1;
 255         filename = ref_file_name(ref);
 256         lock_filename = ref_lock_file_name(ref);
 257         retval = lock_ref_file(filename, lock_filename, old_sha1);
 258         free(filename);
 259         free(lock_filename);
 260         return retval;
 261 }
 262
 263 static int write_ref_file(const char *filename,
 264                           const char *lock_filename, int fd,
 265                           const unsigned char *sha1)
 266 {
 267         char *hex = sha1_to_hex(sha1);
 268         char term = '\n';
 269         if (write(fd, hex, 40) < 40 ||
 270             write(fd, &term, 1) < 1) {
 271                 error("Couldn't write %s\n", filename);
 272                 close(fd);
 273                 return -1;
 274         }
 275         close(fd);
 276         rename(lock_filename, filename);
 277         return 0;
 278 }
 279
 280 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 281 {
 282         char *filename;
 283         char *lock_filename;
 284         int retval;
 285         if (fd < 0)
 286                 return -1;
 287         if (check_ref_format(ref))
 288                 return -1;
 289         filename = ref_file_name(ref);
 290         lock_filename = ref_lock_file_name(ref);
 291         if (safe_create_leading_directories(filename))
 292                 die("unable to create leading directory for %s", filename);
 293         retval = write_ref_file(filename, lock_filename, fd, sha1);
 294         free(filename);
 295         free(lock_filename);
 296         return retval;
 297 }
 298
 299 /*
 300  * Make sure "ref" is something reasonable to have under ".git/refs/";
 301  * We do not like it if:
 302  *
 303  * - any path component of it begins with ".", or
 304  * - it has double dots "..", or
 305  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 306  * - it ends with a "/".
 307  */
 308
 309 static inline int bad_ref_char(int ch)
 310 {
 311         return (((unsigned) ch) <= ' ' ||
 312                 ch == '~' || ch == '^' || ch == ':' ||
 313                 /* 2.13 Pattern Matching Notation */
 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         if (safe_create_leading_directories(filename))
 362                 die("unable to create leading directory for %s", filename);
 363         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 364         if (fd < 0) {
 365                 error("Writing %s", lock_filename);
 366                 perror("Open");
 367         }
 368         retval = write_ref_file(filename, lock_filename, fd, sha1);
 369         free(filename);
 370         free(lock_filename);
 371         return retval;
 372 }