builtin/merge-tree.c

   1 #define USE_THE_INDEX_COMPATIBILITY_MACROS
   2 #include "builtin.h"
   3 #include "tree-walk.h"
   4 #include "xdiff-interface.h"
   5 #include "object-store.h"
   6 #include "repository.h"
   7 #include "blob.h"
   8 #include "exec-cmd.h"
   9 #include "merge-blobs.h"
  10
  11 static const char merge_tree_usage[] = "git merge-tree <base-tree> <branch1> <branch2>";
  12
  13 struct merge_list {
  14         struct merge_list *next;
  15         struct merge_list *link;        /* other stages for this object */
  16
  17         unsigned int stage : 2;
  18         unsigned int mode;
  19         const char *path;
  20         struct blob *blob;
  21 };
  22
  23 static struct merge_list *merge_result, **merge_result_end = &merge_result;
  24
  25 static void add_merge_entry(struct merge_list *entry)
  26 {
  27         *merge_result_end = entry;
  28         merge_result_end = &entry->next;
  29 }
  30
  31 static void merge_trees(struct tree_desc t[3], const char *base);
  32
  33 static const char *explanation(struct merge_list *entry)
  34 {
  35         switch (entry->stage) {
  36         case 0:
  37                 return "merged";
  38         case 3:
  39                 return "added in remote";
  40         case 2:
  41                 if (entry->link)
  42                         return "added in both";
  43                 return "added in local";
  44         }
  45
  46         /* Existed in base */
  47         entry = entry->link;
  48         if (!entry)
  49                 return "removed in both";
  50
  51         if (entry->link)
  52                 return "changed in both";
  53
  54         if (entry->stage == 3)
  55                 return "removed in local";
  56         return "removed in remote";
  57 }
  58
  59 static void *result(struct merge_list *entry, unsigned long *size)
  60 {
  61         enum object_type type;
  62         struct blob *base, *our, *their;
  63         const char *path = entry->path;
  64
  65         if (!entry->stage)
  66                 return read_object_file(&entry->blob->object.oid, &type, size);
  67         base = NULL;
  68         if (entry->stage == 1) {
  69                 base = entry->blob;
  70                 entry = entry->link;
  71         }
  72         our = NULL;
  73         if (entry && entry->stage == 2) {
  74                 our = entry->blob;
  75                 entry = entry->link;
  76         }
  77         their = NULL;
  78         if (entry)
  79                 their = entry->blob;
  80         return merge_blobs(the_repository->index, path,
  81                            base, our, their, size);
  82 }
  83
  84 static void *origin(struct merge_list *entry, unsigned long *size)
  85 {
  86         enum object_type type;
  87         while (entry) {
  88                 if (entry->stage == 2)
  89                         return read_object_file(&entry->blob->object.oid,
  90                                                 &type, size);
  91                 entry = entry->link;
  92         }
  93         return NULL;
  94 }
  95
  96 static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  97 {
  98         int i;
  99         for (i = 0; i < nbuf; i++)
 100                 printf("%.*s", (int) mb[i].size, mb[i].ptr);
 101         return 0;
 102 }
 103
 104 static void show_diff(struct merge_list *entry)
 105 {
 106         unsigned long size;
 107         mmfile_t src, dst;
 108         xpparam_t xpp;
 109         xdemitconf_t xecfg;
 110         xdemitcb_t ecb = { .out_line = show_outf };
 111
 112         memset(&xpp, 0, sizeof(xpp));
 113         xpp.flags = 0;
 114         memset(&xecfg, 0, sizeof(xecfg));
 115         xecfg.ctxlen = 3;
 116
 117         src.ptr = origin(entry, &size);
 118         if (!src.ptr)
 119                 size = 0;
 120         src.size = size;
 121         dst.ptr = result(entry, &size);
 122         if (!dst.ptr)
 123                 size = 0;
 124         dst.size = size;
 125         if (xdi_diff(&src, &dst, &xpp, &xecfg, &ecb))
 126                 die("unable to generate diff");
 127         free(src.ptr);
 128         free(dst.ptr);
 129 }
 130
 131 static void show_result_list(struct merge_list *entry)
 132 {
 133         printf("%s\n", explanation(entry));
 134         do {
 135                 struct merge_list *link = entry->link;
 136                 static const char *desc[4] = { "result", "base", "our", "their" };
 137                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, oid_to_hex(&entry->blob->object.oid), entry->path);
 138                 entry = link;
 139         } while (entry);
 140 }
 141
 142 static void show_result(void)
 143 {
 144         struct merge_list *walk;
 145
 146         walk = merge_result;
 147         while (walk) {
 148                 show_result_list(walk);
 149                 show_diff(walk);
 150                 walk = walk->next;
 151         }
 152 }
 153
 154 /* An empty entry never compares same, not even to another empty entry */
 155 static int same_entry(struct name_entry *a, struct name_entry *b)
 156 {
 157         return  !is_null_oid(&a->oid) &&
 158                 !is_null_oid(&b->oid) &&
 159                 oideq(&a->oid, &b->oid) &&
 160                 a->mode == b->mode;
 161 }
 162
 163 static int both_empty(struct name_entry *a, struct name_entry *b)
 164 {
 165         return is_null_oid(&a->oid) && is_null_oid(&b->oid);
 166 }
 167
 168 static struct merge_list *create_entry(unsigned stage, unsigned mode, const struct object_id *oid, const char *path)
 169 {
 170         struct merge_list *res = xcalloc(1, sizeof(*res));
 171
 172         res->stage = stage;
 173         res->path = path;
 174         res->mode = mode;
 175         res->blob = lookup_blob(the_repository, oid);
 176         return res;
 177 }
 178
 179 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 180 {
 181         struct strbuf buf = STRBUF_INIT;
 182         strbuf_make_traverse_path(&buf, info, n->path, n->pathlen);
 183         return strbuf_detach(&buf, NULL);
 184 }
 185
 186 static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 187 {
 188         struct merge_list *orig, *final;
 189         const char *path;
 190
 191         /* If it's already ours, don't bother showing it */
 192         if (!ours)
 193                 return;
 194
 195         path = traverse_path(info, result);
 196         orig = create_entry(2, ours->mode, &ours->oid, path);
 197         final = create_entry(0, result->mode, &result->oid, path);
 198
 199         final->link = orig;
 200
 201         add_merge_entry(final);
 202 }
 203
 204 static void unresolved_directory(const struct traverse_info *info,
 205                                  struct name_entry n[3])
 206 {
 207         struct repository *r = the_repository;
 208         char *newbase;
 209         struct name_entry *p;
 210         struct tree_desc t[3];
 211         void *buf0, *buf1, *buf2;
 212
 213         for (p = n; p < n + 3; p++) {
 214                 if (p->mode && S_ISDIR(p->mode))
 215                         break;
 216         }
 217         if (n + 3 <= p)
 218                 return; /* there is no tree here */
 219
 220         newbase = traverse_path(info, p);
 221
 222 #define ENTRY_OID(e) (((e)->mode && S_ISDIR((e)->mode)) ? &(e)->oid : NULL)
 223         buf0 = fill_tree_descriptor(r, t + 0, ENTRY_OID(n + 0));
 224         buf1 = fill_tree_descriptor(r, t + 1, ENTRY_OID(n + 1));
 225         buf2 = fill_tree_descriptor(r, t + 2, ENTRY_OID(n + 2));
 226 #undef ENTRY_OID
 227
 228         merge_trees(t, newbase);
 229
 230         free(buf0);
 231         free(buf1);
 232         free(buf2);
 233         free(newbase);
 234 }
 235
 236
 237 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 238 {
 239         const char *path;
 240         struct merge_list *link;
 241
 242         if (!n->mode)
 243                 return entry;
 244         if (entry)
 245                 path = entry->path;
 246         else
 247                 path = traverse_path(info, n);
 248         link = create_entry(stage, n->mode, &n->oid, path);
 249         link->link = entry;
 250         return link;
 251 }
 252
 253 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 254 {
 255         struct merge_list *entry = NULL;
 256         int i;
 257         unsigned dirmask = 0, mask = 0;
 258
 259         for (i = 0; i < 3; i++) {
 260                 mask |= (1 << i);
 261                 /*
 262                  * Treat missing entries as directories so that we return
 263                  * after unresolved_directory has handled this.
 264                  */
 265                 if (!n[i].mode || S_ISDIR(n[i].mode))
 266                         dirmask |= (1 << i);
 267         }
 268
 269         unresolved_directory(info, n);
 270
 271         if (dirmask == mask)
 272                 return;
 273
 274         if (n[2].mode && !S_ISDIR(n[2].mode))
 275                 entry = link_entry(3, info, n + 2, entry);
 276         if (n[1].mode && !S_ISDIR(n[1].mode))
 277                 entry = link_entry(2, info, n + 1, entry);
 278         if (n[0].mode && !S_ISDIR(n[0].mode))
 279                 entry = link_entry(1, info, n + 0, entry);
 280
 281         add_merge_entry(entry);
 282 }
 283
 284 /*
 285  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 286  * as the origin.
 287  *
 288  * This walks the (sorted) trees in lock-step, checking every possible
 289  * name. Note that directories automatically sort differently from other
 290  * files (see "base_name_compare"), so you'll never see file/directory
 291  * conflicts, because they won't ever compare the same.
 292  *
 293  * IOW, if a directory changes to a filename, it will automatically be
 294  * seen as the directory going away, and the filename being created.
 295  *
 296  * Think of this as a three-way diff.
 297  *
 298  * The output will be either:
 299  *  - successful merge
 300  *       "0 mode sha1 filename"
 301  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 302  *    in parallel with this too!
 303  *
 304  *  - conflict:
 305  *      "1 mode sha1 filename"
 306  *      "2 mode sha1 filename"
 307  *      "3 mode sha1 filename"
 308  *    where not all of the 1/2/3 lines may exist, of course.
 309  *
 310  * The successful merge rules are the same as for the three-way merge
 311  * in git-read-tree.
 312  */
 313 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 314 {
 315         /* Same in both? */
 316         if (same_entry(entry+1, entry+2) || both_empty(entry+1, entry+2)) {
 317                 /* Modified, added or removed identically */
 318                 resolve(info, NULL, entry+1);
 319                 return mask;
 320         }
 321
 322         if (same_entry(entry+0, entry+1)) {
 323                 if (!is_null_oid(&entry[2].oid) && !S_ISDIR(entry[2].mode)) {
 324                         /* We did not touch, they modified -- take theirs */
 325                         resolve(info, entry+1, entry+2);
 326                         return mask;
 327                 }
 328                 /*
 329                  * If we did not touch a directory but they made it
 330                  * into a file, we fall through and unresolved()
 331                  * recurses down.  Likewise for the opposite case.
 332                  */
 333         }
 334
 335         if (same_entry(entry+0, entry+2) || both_empty(entry+0, entry+2)) {
 336                 /* We added, modified or removed, they did not touch -- take ours */
 337                 resolve(info, NULL, entry+1);
 338                 return mask;
 339         }
 340
 341         unresolved(info, entry);
 342         return mask;
 343 }
 344
 345 static void merge_trees(struct tree_desc t[3], const char *base)
 346 {
 347         struct traverse_info info;
 348
 349         setup_traverse_info(&info, base);
 350         info.fn = threeway_callback;
 351         traverse_trees(&the_index, 3, t, &info);
 352 }
 353
 354 static void *get_tree_descriptor(struct repository *r,
 355                                  struct tree_desc *desc,
 356                                  const char *rev)
 357 {
 358         struct object_id oid;
 359         void *buf;
 360
 361         if (repo_get_oid(r, rev, &oid))
 362                 die("unknown rev %s", rev);
 363         buf = fill_tree_descriptor(r, desc, &oid);
 364         if (!buf)
 365                 die("%s is not a tree", rev);
 366         return buf;
 367 }
 368
 369 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 370 {
 371         struct repository *r = the_repository;
 372         struct tree_desc t[3];
 373         void *buf1, *buf2, *buf3;
 374
 375         if (argc != 4)
 376                 usage(merge_tree_usage);
 377
 378         buf1 = get_tree_descriptor(r, t+0, argv[1]);
 379         buf2 = get_tree_descriptor(r, t+1, argv[2]);
 380         buf3 = get_tree_descriptor(r, t+2, argv[3]);
 381         merge_trees(t, "");
 382         free(buf1);
 383         free(buf2);
 384         free(buf3);
 385
 386         show_result();
 387         return 0;
 388 }