builtin/merge-tree.c

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