builtin/merge-tree.c

   1 #include "builtin.h"
   2 #include "tree-walk.h"
   3 #include "xdiff-interface.h"
   4 #include "blob.h"
   5 #include "exec_cmd.h"
   6 #include "merge-blobs.h"
   7
   8 static const char merge_tree_usage[] = "git merge-tree <base-tree> <branch1> <branch2>";
   9
  10 struct merge_list {
  11         struct merge_list *next;
  12         struct merge_list *link;        /* other stages for this object */
  13
  14         unsigned int stage : 2;
  15         unsigned int mode;
  16         const char *path;
  17         struct blob *blob;
  18 };
  19
  20 static struct merge_list *merge_result, **merge_result_end = &merge_result;
  21
  22 static void add_merge_entry(struct merge_list *entry)
  23 {
  24         *merge_result_end = entry;
  25         merge_result_end = &entry->next;
  26 }
  27
  28 static void merge_trees(struct tree_desc t[3], const char *base);
  29
  30 static const char *explanation(struct merge_list *entry)
  31 {
  32         switch (entry->stage) {
  33         case 0:
  34                 return "merged";
  35         case 3:
  36                 return "added in remote";
  37         case 2:
  38                 if (entry->link)
  39                         return "added in both";
  40                 return "added in local";
  41         }
  42
  43         /* Existed in base */
  44         entry = entry->link;
  45         if (!entry)
  46                 return "removed in both";
  47
  48         if (entry->link)
  49                 return "changed in both";
  50
  51         if (entry->stage == 3)
  52                 return "removed in local";
  53         return "removed in remote";
  54 }
  55
  56 static void *result(struct merge_list *entry, unsigned long *size)
  57 {
  58         enum object_type type;
  59         struct blob *base, *our, *their;
  60         const char *path = entry->path;
  61
  62         if (!entry->stage)
  63                 return read_sha1_file(get_object_hash(entry->blob->object), &type, size);
  64         base = NULL;
  65         if (entry->stage == 1) {
  66                 base = entry->blob;
  67                 entry = entry->link;
  68         }
  69         our = NULL;
  70         if (entry && entry->stage == 2) {
  71                 our = entry->blob;
  72                 entry = entry->link;
  73         }
  74         their = NULL;
  75         if (entry)
  76                 their = entry->blob;
  77         return merge_blobs(path, base, our, their, size);
  78 }
  79
  80 static void *origin(struct merge_list *entry, unsigned long *size)
  81 {
  82         enum object_type type;
  83         while (entry) {
  84                 if (entry->stage == 2)
  85                         return read_sha1_file(get_object_hash(entry->blob->object), &type, size);
  86                 entry = entry->link;
  87         }
  88         return NULL;
  89 }
  90
  91 static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  92 {
  93         int i;
  94         for (i = 0; i < nbuf; i++)
  95                 printf("%.*s", (int) mb[i].size, mb[i].ptr);
  96         return 0;
  97 }
  98
  99 static void show_diff(struct merge_list *entry)
 100 {
 101         unsigned long size;
 102         mmfile_t src, dst;
 103         xpparam_t xpp;
 104         xdemitconf_t xecfg;
 105         xdemitcb_t ecb;
 106
 107         xpp.flags = 0;
 108         memset(&xecfg, 0, sizeof(xecfg));
 109         xecfg.ctxlen = 3;
 110         ecb.outf = show_outf;
 111         ecb.priv = NULL;
 112
 113         src.ptr = origin(entry, &size);
 114         if (!src.ptr)
 115                 size = 0;
 116         src.size = size;
 117         dst.ptr = result(entry, &size);
 118         if (!dst.ptr)
 119                 size = 0;
 120         dst.size = size;
 121         if (xdi_diff(&src, &dst, &xpp, &xecfg, &ecb))
 122                 die("unable to generate diff");
 123         free(src.ptr);
 124         free(dst.ptr);
 125 }
 126
 127 static void show_result_list(struct merge_list *entry)
 128 {
 129         printf("%s\n", explanation(entry));
 130         do {
 131                 struct merge_list *link = entry->link;
 132                 static const char *desc[4] = { "result", "base", "our", "their" };
 133                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, oid_to_hex(&entry->blob->object.oid), entry->path);
 134                 entry = link;
 135         } while (entry);
 136 }
 137
 138 static void show_result(void)
 139 {
 140         struct merge_list *walk;
 141
 142         walk = merge_result;
 143         while (walk) {
 144                 show_result_list(walk);
 145                 show_diff(walk);
 146                 walk = walk->next;
 147         }
 148 }
 149
 150 /* An empty entry never compares same, not even to another empty entry */
 151 static int same_entry(struct name_entry *a, struct name_entry *b)
 152 {
 153         return  a->sha1 &&
 154                 b->sha1 &&
 155                 !hashcmp(a->sha1, b->sha1) &&
 156                 a->mode == b->mode;
 157 }
 158
 159 static int both_empty(struct name_entry *a, struct name_entry *b)
 160 {
 161         return !(a->sha1 || b->sha1);
 162 }
 163
 164 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 165 {
 166         struct merge_list *res = xcalloc(1, sizeof(*res));
 167
 168         res->stage = stage;
 169         res->path = path;
 170         res->mode = mode;
 171         res->blob = lookup_blob(sha1);
 172         return res;
 173 }
 174
 175 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 176 {
 177         char *path = xmalloc(traverse_path_len(info, n) + 1);
 178         return make_traverse_path(path, info, n);
 179 }
 180
 181 static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 182 {
 183         struct merge_list *orig, *final;
 184         const char *path;
 185
 186         /* If it's already ours, don't bother showing it */
 187         if (!ours)
 188                 return;
 189
 190         path = traverse_path(info, result);
 191         orig = create_entry(2, ours->mode, ours->sha1, path);
 192         final = create_entry(0, result->mode, result->sha1, path);
 193
 194         final->link = orig;
 195
 196         add_merge_entry(final);
 197 }
 198
 199 static void unresolved_directory(const struct traverse_info *info,
 200                                  struct name_entry n[3])
 201 {
 202         char *newbase;
 203         struct name_entry *p;
 204         struct tree_desc t[3];
 205         void *buf0, *buf1, *buf2;
 206
 207         for (p = n; p < n + 3; p++) {
 208                 if (p->mode && S_ISDIR(p->mode))
 209                         break;
 210         }
 211         if (n + 3 <= p)
 212                 return; /* there is no tree here */
 213
 214         newbase = traverse_path(info, p);
 215
 216 #define ENTRY_SHA1(e) (((e)->mode && S_ISDIR((e)->mode)) ? (e)->sha1 : NULL)
 217         buf0 = fill_tree_descriptor(t+0, ENTRY_SHA1(n + 0));
 218         buf1 = fill_tree_descriptor(t+1, ENTRY_SHA1(n + 1));
 219         buf2 = fill_tree_descriptor(t+2, ENTRY_SHA1(n + 2));
 220 #undef ENTRY_SHA1
 221
 222         merge_trees(t, newbase);
 223
 224         free(buf0);
 225         free(buf1);
 226         free(buf2);
 227         free(newbase);
 228 }
 229
 230
 231 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 232 {
 233         const char *path;
 234         struct merge_list *link;
 235
 236         if (!n->mode)
 237                 return entry;
 238         if (entry)
 239                 path = entry->path;
 240         else
 241                 path = traverse_path(info, n);
 242         link = create_entry(stage, n->mode, n->sha1, path);
 243         link->link = entry;
 244         return link;
 245 }
 246
 247 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 248 {
 249         struct merge_list *entry = NULL;
 250         int i;
 251         unsigned dirmask = 0, mask = 0;
 252
 253         for (i = 0; i < 3; i++) {
 254                 mask |= (1 << i);
 255                 /*
 256                  * Treat missing entries as directories so that we return
 257                  * after unresolved_directory has handled this.
 258                  */
 259                 if (!n[i].mode || S_ISDIR(n[i].mode))
 260                         dirmask |= (1 << i);
 261         }
 262
 263         unresolved_directory(info, n);
 264
 265         if (dirmask == mask)
 266                 return;
 267
 268         if (n[2].mode && !S_ISDIR(n[2].mode))
 269                 entry = link_entry(3, info, n + 2, entry);
 270         if (n[1].mode && !S_ISDIR(n[1].mode))
 271                 entry = link_entry(2, info, n + 1, entry);
 272         if (n[0].mode && !S_ISDIR(n[0].mode))
 273                 entry = link_entry(1, info, n + 0, entry);
 274
 275         add_merge_entry(entry);
 276 }
 277
 278 /*
 279  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 280  * as the origin.
 281  *
 282  * This walks the (sorted) trees in lock-step, checking every possible
 283  * name. Note that directories automatically sort differently from other
 284  * files (see "base_name_compare"), so you'll never see file/directory
 285  * conflicts, because they won't ever compare the same.
 286  *
 287  * IOW, if a directory changes to a filename, it will automatically be
 288  * seen as the directory going away, and the filename being created.
 289  *
 290  * Think of this as a three-way diff.
 291  *
 292  * The output will be either:
 293  *  - successful merge
 294  *       "0 mode sha1 filename"
 295  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 296  *    in parallel with this too!
 297  *
 298  *  - conflict:
 299  *      "1 mode sha1 filename"
 300  *      "2 mode sha1 filename"
 301  *      "3 mode sha1 filename"
 302  *    where not all of the 1/2/3 lines may exist, of course.
 303  *
 304  * The successful merge rules are the same as for the three-way merge
 305  * in git-read-tree.
 306  */
 307 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 308 {
 309         /* Same in both? */
 310         if (same_entry(entry+1, entry+2) || both_empty(entry+1, entry+2)) {
 311                 /* Modified, added or removed identically */
 312                 resolve(info, NULL, entry+1);
 313                 return mask;
 314         }
 315
 316         if (same_entry(entry+0, entry+1)) {
 317                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 318                         /* We did not touch, they modified -- take theirs */
 319                         resolve(info, entry+1, entry+2);
 320                         return mask;
 321                 }
 322                 /*
 323                  * If we did not touch a directory but they made it
 324                  * into a file, we fall through and unresolved()
 325                  * recurses down.  Likewise for the opposite case.
 326                  */
 327         }
 328
 329         if (same_entry(entry+0, entry+2) || both_empty(entry+0, entry+2)) {
 330                 /* We added, modified or removed, they did not touch -- take ours */
 331                 resolve(info, NULL, entry+1);
 332                 return mask;
 333         }
 334
 335         unresolved(info, entry);
 336         return mask;
 337 }
 338
 339 static void merge_trees(struct tree_desc t[3], const char *base)
 340 {
 341         struct traverse_info info;
 342
 343         setup_traverse_info(&info, base);
 344         info.fn = threeway_callback;
 345         traverse_trees(3, t, &info);
 346 }
 347
 348 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 349 {
 350         unsigned char sha1[20];
 351         void *buf;
 352
 353         if (get_sha1(rev, sha1))
 354                 die("unknown rev %s", rev);
 355         buf = fill_tree_descriptor(desc, sha1);
 356         if (!buf)
 357                 die("%s is not a tree", rev);
 358         return buf;
 359 }
 360
 361 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 362 {
 363         struct tree_desc t[3];
 364         void *buf1, *buf2, *buf3;
 365
 366         if (argc != 4)
 367                 usage(merge_tree_usage);
 368
 369         buf1 = get_tree_descriptor(t+0, argv[1]);
 370         buf2 = get_tree_descriptor(t+1, argv[2]);
 371         buf3 = get_tree_descriptor(t+2, argv[3]);
 372         merge_trees(t, "");
 373         free(buf1);
 374         free(buf2);
 375         free(buf3);
 376
 377         show_result();
 378         return 0;
 379 }