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