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