read-tree.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #include "cache.h"
   7
   8 static int stage = 0;
   9
  10 static int read_one_entry(unsigned char *sha1, const char *base, int baselen, const char *pathname, unsigned mode)
  11 {
  12         int len = strlen(pathname);
  13         unsigned int size = cache_entry_size(baselen + len);
  14         struct cache_entry *ce = malloc(size);
  15
  16         memset(ce, 0, size);
  17
  18         ce->ce_mode = create_ce_mode(mode);
  19         ce->ce_flags = create_ce_flags(baselen + len, stage);
  20         memcpy(ce->name, base, baselen);
  21         memcpy(ce->name + baselen, pathname, len+1);
  22         memcpy(ce->sha1, sha1, 20);
  23         return add_cache_entry(ce, 1);
  24 }
  25
  26 static int read_tree_recursive(void *buffer, unsigned long size,
  27                                const char *base, int baselen)
  28 {
  29         while (size) {
  30                 int len = strlen(buffer)+1;
  31                 unsigned char *sha1 = buffer + len;
  32                 char *path = strchr(buffer, ' ')+1;
  33                 unsigned int mode;
  34
  35                 if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
  36                         return -1;
  37
  38                 buffer = sha1 + 20;
  39                 size -= len + 20;
  40
  41                 if (S_ISDIR(mode)) {
  42                         int retval;
  43                         int pathlen = strlen(path);
  44                         char *newbase = malloc(baselen + 1 + pathlen);
  45                         void *eltbuf;
  46                         char elttype[20];
  47                         unsigned long eltsize;
  48
  49                         eltbuf = read_sha1_file(sha1, elttype, &eltsize);
  50                         if (!eltbuf || strcmp(elttype, "tree"))
  51                                 return -1;
  52                         memcpy(newbase, base, baselen);
  53                         memcpy(newbase + baselen, path, pathlen);
  54                         newbase[baselen + pathlen] = '/';
  55                         retval = read_tree_recursive(eltbuf, eltsize,
  56                                                      newbase,
  57                                                      baselen + pathlen + 1);
  58                         free(eltbuf);
  59                         free(newbase);
  60                         if (retval)
  61                                 return -1;
  62                         continue;
  63                 }
  64                 if (read_one_entry(sha1, base, baselen, path, mode) < 0)
  65                         return -1;
  66         }
  67         return 0;
  68 }
  69
  70 static int read_tree(unsigned char *sha1, const char *base, int baselen)
  71 {
  72         void *buffer;
  73         unsigned long size;
  74
  75         buffer = read_tree_with_tree_or_commit_sha1(sha1, &size, 0);
  76         if (!buffer)
  77                 return -1;
  78         return read_tree_recursive(buffer, size, base, baselen);
  79 }
  80
  81 static char *lockfile_name;
  82
  83 static void remove_lock_file(void)
  84 {
  85         if (lockfile_name)
  86                 unlink(lockfile_name);
  87 }
  88
  89 static int path_matches(struct cache_entry *a, struct cache_entry *b)
  90 {
  91         int len = ce_namelen(a);
  92         return ce_namelen(b) == len &&
  93                 !memcmp(a->name, b->name, len);
  94 }
  95
  96 static int same(struct cache_entry *a, struct cache_entry *b)
  97 {
  98         return a->ce_mode == b->ce_mode &&
  99                 !memcmp(a->sha1, b->sha1, 20);
 100 }
 101
 102
 103 /*
 104  * This removes all trivial merges that don't change the tree
 105  * and collapses them to state 0.
 106  *
 107  * _Any_ other merge is left to user policy.  That includes "both
 108  * created the same file", and "both removed the same file" - which are
 109  * trivial, but the user might still want to _note_ it.
 110  */
 111 static struct cache_entry *merge_entries(struct cache_entry *a,
 112                                          struct cache_entry *b,
 113                                          struct cache_entry *c)
 114 {
 115         int len = ce_namelen(a);
 116
 117         /*
 118          * Are they all the same filename? We won't do
 119          * any name merging
 120          */
 121         if (ce_namelen(b) != len ||
 122             ce_namelen(c) != len ||
 123             memcmp(a->name, b->name, len) ||
 124             memcmp(a->name, c->name, len))
 125                 return NULL;
 126
 127         /*
 128          * Ok, all three entries describe the same
 129          * filename, but maybe the contents or file
 130          * mode have changed?
 131          *
 132          * The trivial cases end up being the ones where two
 133          * out of three files are the same:
 134          *  - both destinations the same, trivially take either
 135          *  - one of the destination versions hasn't changed,
 136          *    take the other.
 137          *
 138          * The "all entries exactly the same" case falls out as
 139          * a special case of any of the "two same" cases.
 140          *
 141          * Here "a" is "original", and "b" and "c" are the two
 142          * trees we are merging.
 143          */
 144         if (same(b,c))
 145                 return c;
 146         if (same(a,b))
 147                 return c;
 148         if (same(a,c))
 149                 return b;
 150         return NULL;
 151 }
 152
 153 static void trivially_merge_cache(struct cache_entry **src, int nr)
 154 {
 155         static struct cache_entry null_entry;
 156         struct cache_entry **dst = src;
 157         struct cache_entry *old = &null_entry;
 158
 159         while (nr) {
 160                 struct cache_entry *ce, *result;
 161
 162                 ce = src[0];
 163
 164                 /* We throw away original cache entries except for the stat information */
 165                 if (!ce_stage(ce)) {
 166                         old = ce;
 167                         src++;
 168                         nr--;
 169                         active_nr--;
 170                         continue;
 171                 }
 172                 if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
 173                         /*
 174                          * See if we can re-use the old CE directly?
 175                          * That way we get the uptodate stat info.
 176                          */
 177                         if (path_matches(result, old) && same(result, old))
 178                                 *result = *old;
 179                         ce = result;
 180                         ce->ce_flags &= ~htons(CE_STAGEMASK);
 181                         src += 2;
 182                         nr -= 2;
 183                         active_nr -= 2;
 184                 }
 185                 *dst++ = ce;
 186                 src++;
 187                 nr--;
 188         }
 189 }
 190
 191 static void merge_stat_info(struct cache_entry **src, int nr)
 192 {
 193         static struct cache_entry null_entry;
 194         struct cache_entry **dst = src;
 195         struct cache_entry *old = &null_entry;
 196
 197         while (nr) {
 198                 struct cache_entry *ce;
 199
 200                 ce = src[0];
 201
 202                 /* We throw away original cache entries except for the stat information */
 203                 if (!ce_stage(ce)) {
 204                         old = ce;
 205                         src++;
 206                         nr--;
 207                         active_nr--;
 208                         continue;
 209                 }
 210                 if (path_matches(ce, old) && same(ce, old))
 211                         *ce = *old;
 212                 ce->ce_flags &= ~htons(CE_STAGEMASK);
 213                 *dst++ = ce;
 214                 src++;
 215                 nr--;
 216         }
 217 }
 218
 219 static char *read_tree_usage = "read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
 220
 221 int main(int argc, char **argv)
 222 {
 223         int i, newfd, merge;
 224         unsigned char sha1[20];
 225         static char lockfile[MAXPATHLEN+1];
 226         const char *indexfile = get_index_file();
 227
 228         snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
 229
 230         newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
 231         if (newfd < 0)
 232                 die("unable to create new cachefile");
 233         atexit(remove_lock_file);
 234         lockfile_name = lockfile;
 235
 236         merge = 0;
 237         for (i = 1; i < argc; i++) {
 238                 const char *arg = argv[i];
 239
 240                 /* "-m" stands for "merge", meaning we start in stage 1 */
 241                 if (!strcmp(arg, "-m")) {
 242                         int i;
 243                         if (stage)
 244                                 die("-m needs to come first");
 245                         read_cache();
 246                         for (i = 0; i < active_nr; i++) {
 247                                 if (ce_stage(active_cache[i]))
 248                                         die("you need to resolve your current index first");
 249                         }
 250                         stage = 1;
 251                         merge = 1;
 252                         continue;
 253                 }
 254                 if (get_sha1_hex(arg, sha1) < 0)
 255                         usage(read_tree_usage);
 256                 if (stage > 3)
 257                         usage(read_tree_usage);
 258                 if (read_tree(sha1, "", 0) < 0)
 259                         die("failed to unpack tree object %s", arg);
 260                 stage++;
 261         }
 262         if (merge) {
 263                 switch (stage) {
 264                 case 4: /* Three-way merge */
 265                         trivially_merge_cache(active_cache, active_nr);
 266                         break;
 267                 case 2: /* Just read a tree, merge with old cache contents */
 268                         merge_stat_info(active_cache, active_nr);
 269                         break;
 270                 default:
 271                         die("just how do you expect me to merge %d trees?", stage-1);
 272                 }
 273         }
 274         if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
 275                 die("unable to write new index file");
 276         lockfile_name = NULL;
 277         return 0;
 278 }