Andrew's git / gitweb.git / refs.c
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refs.con commit create_symref: if symlink fails, fall back to writing a "symbolic ref" (303958d)
   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
  13int validate_symref(const char *path)
  14{
  15        struct stat st;
  16        char *buf, buffer[256];
  17        int len, fd;
  18
  19        if (lstat(path, &st) < 0)
  20                return -1;
  21
  22        /* Make sure it is a "refs/.." symlink */
  23        if (S_ISLNK(st.st_mode)) {
  24                len = readlink(path, buffer, sizeof(buffer)-1);
  25                if (len >= 5 && !memcmp("refs/", buffer, 5))
  26                        return 0;
  27                return -1;
  28        }
  29
  30        /*
  31         * Anything else, just open it and try to see if it is a symbolic ref.
  32         */
  33        fd = open(path, O_RDONLY);
  34        if (fd < 0)
  35                return -1;
  36        len = read(fd, buffer, sizeof(buffer)-1);
  37        close(fd);
  38
  39        /*
  40         * Is it a symbolic ref?
  41         */
  42        if (len < 4 || memcmp("ref:", buffer, 4))
  43                return -1;
  44        buf = buffer + 4;
  45        len -= 4;
  46        while (len && isspace(*buf))
  47                buf++, len--;
  48        if (len >= 5 && !memcmp("refs/", buf, 5))
  49                return 0;
  50        return -1;
  51}
  52
  53const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  54{
  55        int depth = MAXDEPTH, len;
  56        char buffer[256];
  57
  58        for (;;) {
  59                struct stat st;
  60                char *buf;
  61                int fd;
  62
  63                if (--depth < 0)
  64                        return NULL;
  65
  66                /* Special case: non-existing file.
  67                 * Not having the refs/heads/new-branch is OK
  68                 * if we are writing into it, so is .git/HEAD
  69                 * that points at refs/heads/master still to be
  70                 * born.  It is NOT OK if we are resolving for
  71                 * reading.
  72                 */
  73                if (lstat(path, &st) < 0) {
  74                        if (reading || errno != ENOENT)
  75                                return NULL;
  76                        memset(sha1, 0, 20);
  77                        return path;
  78                }
  79
  80                /* Follow "normalized" - ie "refs/.." symlinks by hand */
  81                if (S_ISLNK(st.st_mode)) {
  82                        len = readlink(path, buffer, sizeof(buffer)-1);
  83                        if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  84                                path = git_path("%.*s", len, buffer);
  85                                continue;
  86                        }
  87                }
  88
  89                /*
  90                 * Anything else, just open it and try to use it as
  91                 * a ref
  92                 */
  93                fd = open(path, O_RDONLY);
  94                if (fd < 0)
  95                        return NULL;
  96                len = read(fd, buffer, sizeof(buffer)-1);
  97                close(fd);
  98
  99                /*
 100                 * Is it a symbolic ref?
 101                 */
 102                if (len < 4 || memcmp("ref:", buffer, 4))
 103                        break;
 104                buf = buffer + 4;
 105                len -= 4;
 106                while (len && isspace(*buf))
 107                        buf++, len--;
 108                while (len && isspace(buf[len-1]))
 109                        buf[--len] = 0;
 110                path = git_path("%.*s", len, buf);
 111        }
 112        if (len < 40 || get_sha1_hex(buffer, sha1))
 113                return NULL;
 114        return path;
 115}
 116
 117int create_symref(const char *git_HEAD, const char *refs_heads_master)
 118{
 119        const char *lockpath;
 120        char ref[1000];
 121        int fd, len, written;
 122
 123#if USE_SYMLINK_HEAD
 124        unlink(git_HEAD);
 125        if (!symlink(refs_heads_master, git_HEAD))
 126                return 0;
 127        fprintf(stderr, "no symlink - falling back to symbolic ref\n");
 128#endif
 129
 130        len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 131        if (sizeof(ref) <= len) {
 132                error("refname too long: %s", refs_heads_master);
 133                return -1;
 134        }
 135        lockpath = mkpath("%s.lock", git_HEAD);
 136        fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666); 
 137        written = write(fd, ref, len);
 138        close(fd);
 139        if (written != len) {
 140                unlink(lockpath);
 141                error("Unable to write to %s", lockpath);
 142                return -2;
 143        }
 144        if (rename(lockpath, git_HEAD) < 0) {
 145                unlink(lockpath);
 146                error("Unable to create %s", git_HEAD);
 147                return -3;
 148        }
 149        return 0;
 150}
 151
 152int read_ref(const char *filename, unsigned char *sha1)
 153{
 154        if (resolve_ref(filename, sha1, 1))
 155                return 0;
 156        return -1;
 157}
 158
 159static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 160{
 161        int retval = 0;
 162        DIR *dir = opendir(git_path("%s", base));
 163
 164        if (dir) {
 165                struct dirent *de;
 166                int baselen = strlen(base);
 167                char *path = xmalloc(baselen + 257);
 168
 169                if (!strncmp(base, "./", 2)) {
 170                        base += 2;
 171                        baselen -= 2;
 172                }
 173                memcpy(path, base, baselen);
 174                if (baselen && base[baselen-1] != '/')
 175                        path[baselen++] = '/';
 176
 177                while ((de = readdir(dir)) != NULL) {
 178                        unsigned char sha1[20];
 179                        struct stat st;
 180                        int namelen;
 181
 182                        if (de->d_name[0] == '.')
 183                                continue;
 184                        namelen = strlen(de->d_name);
 185                        if (namelen > 255)
 186                                continue;
 187                        memcpy(path + baselen, de->d_name, namelen+1);
 188                        if (stat(git_path("%s", path), &st) < 0)
 189                                continue;
 190                        if (S_ISDIR(st.st_mode)) {
 191                                retval = do_for_each_ref(path, fn);
 192                                if (retval)
 193                                        break;
 194                                continue;
 195                        }
 196                        if (read_ref(git_path("%s", path), sha1) < 0)
 197                                continue;
 198                        if (!has_sha1_file(sha1))
 199                                continue;
 200                        retval = fn(path, sha1);
 201                        if (retval)
 202                                break;
 203                }
 204                free(path);
 205                closedir(dir);
 206        }
 207        return retval;
 208}
 209
 210int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 211{
 212        unsigned char sha1[20];
 213        if (!read_ref(git_path("HEAD"), sha1))
 214                return fn("HEAD", sha1);
 215        return 0;
 216}
 217
 218int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 219{
 220        return do_for_each_ref("refs", fn);
 221}
 222
 223static char *ref_file_name(const char *ref)
 224{
 225        char *base = get_refs_directory();
 226        int baselen = strlen(base);
 227        int reflen = strlen(ref);
 228        char *ret = xmalloc(baselen + 2 + reflen);
 229        sprintf(ret, "%s/%s", base, ref);
 230        return ret;
 231}
 232
 233static char *ref_lock_file_name(const char *ref)
 234{
 235        char *base = get_refs_directory();
 236        int baselen = strlen(base);
 237        int reflen = strlen(ref);
 238        char *ret = xmalloc(baselen + 7 + reflen);
 239        sprintf(ret, "%s/%s.lock", base, ref);
 240        return ret;
 241}
 242
 243int get_ref_sha1(const char *ref, unsigned char *sha1)
 244{
 245        const char *filename;
 246
 247        if (check_ref_format(ref))
 248                return -1;
 249        filename = git_path("refs/%s", ref);
 250        return read_ref(filename, sha1);
 251}
 252
 253static int lock_ref_file(const char *filename, const char *lock_filename,
 254                         const unsigned char *old_sha1)
 255{
 256        int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 257        unsigned char current_sha1[20];
 258        int retval;
 259        if (fd < 0) {
 260                return error("Couldn't open lock file for %s: %s",
 261                             filename, strerror(errno));
 262        }
 263        retval = read_ref(filename, current_sha1);
 264        if (old_sha1) {
 265                if (retval) {
 266                        close(fd);
 267                        unlink(lock_filename);
 268                        return error("Could not read the current value of %s",
 269                                     filename);
 270                }
 271                if (memcmp(current_sha1, old_sha1, 20)) {
 272                        close(fd);
 273                        unlink(lock_filename);
 274                        error("The current value of %s is %s",
 275                              filename, sha1_to_hex(current_sha1));
 276                        return error("Expected %s",
 277                                     sha1_to_hex(old_sha1));
 278                }
 279        } else {
 280                if (!retval) {
 281                        close(fd);
 282                        unlink(lock_filename);
 283                        return error("Unexpectedly found a value of %s for %s",
 284                                     sha1_to_hex(current_sha1), filename);
 285                }
 286        }
 287        return fd;
 288}
 289
 290int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 291{
 292        char *filename;
 293        char *lock_filename;
 294        int retval;
 295        if (check_ref_format(ref))
 296                return -1;
 297        filename = ref_file_name(ref);
 298        lock_filename = ref_lock_file_name(ref);
 299        retval = lock_ref_file(filename, lock_filename, old_sha1);
 300        free(filename);
 301        free(lock_filename);
 302        return retval;
 303}
 304
 305static int write_ref_file(const char *filename,
 306                          const char *lock_filename, int fd,
 307                          const unsigned char *sha1)
 308{
 309        char *hex = sha1_to_hex(sha1);
 310        char term = '\n';
 311        if (write(fd, hex, 40) < 40 ||
 312            write(fd, &term, 1) < 1) {
 313                error("Couldn't write %s\n", filename);
 314                close(fd);
 315                return -1;
 316        }
 317        close(fd);
 318        rename(lock_filename, filename);
 319        return 0;
 320}
 321
 322int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 323{
 324        char *filename;
 325        char *lock_filename;
 326        int retval;
 327        if (fd < 0)
 328                return -1;
 329        if (check_ref_format(ref))
 330                return -1;
 331        filename = ref_file_name(ref);
 332        lock_filename = ref_lock_file_name(ref);
 333        retval = write_ref_file(filename, lock_filename, fd, sha1);
 334        free(filename);
 335        free(lock_filename);
 336        return retval;
 337}
 338
 339/*
 340 * Make sure "ref" is something reasonable to have under ".git/refs/";
 341 * We do not like it if:
 342 *
 343 * - any path component of it begins with ".", or
 344 * - it has double dots "..", or
 345 * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 346 * - it ends with a "/".
 347 */
 348
 349static inline int bad_ref_char(int ch)
 350{
 351        return (((unsigned) ch) <= ' ' ||
 352                ch == '~' || ch == '^' || ch == ':');
 353}
 354
 355int check_ref_format(const char *ref)
 356{
 357        int ch, level;
 358        const char *cp = ref;
 359
 360        level = 0;
 361        while (1) {
 362                while ((ch = *cp++) == '/')
 363                        ; /* tolerate duplicated slashes */
 364                if (!ch)
 365                        return -1; /* should not end with slashes */
 366
 367                /* we are at the beginning of the path component */
 368                if (ch == '.' || bad_ref_char(ch))
 369                        return -1;
 370
 371                /* scan the rest of the path component */
 372                while ((ch = *cp++) != 0) {
 373                        if (bad_ref_char(ch))
 374                                return -1;
 375                        if (ch == '/')
 376                                break;
 377                        if (ch == '.' && *cp == '.')
 378                                return -1;
 379                }
 380                level++;
 381                if (!ch) {
 382                        if (level < 2)
 383                                return -1; /* at least of form "heads/blah" */
 384                        return 0;
 385                }
 386        }
 387}
 388
 389int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 390{
 391        char *filename;
 392        char *lock_filename;
 393        int fd;
 394        int retval;
 395        if (check_ref_format(ref))
 396                return -1;
 397        filename = ref_file_name(ref);
 398        lock_filename = ref_lock_file_name(ref);
 399        fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 400        if (fd < 0) {
 401                error("Writing %s", lock_filename);
 402                perror("Open");
 403        }
 404        retval = write_ref_file(filename, lock_filename, fd, sha1);
 405        free(filename);
 406        free(lock_filename);
 407        return retval;
 408}