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.outf = show_outf;
 114         ecb.priv = NULL;
 115
 116         src.ptr = origin(entry, &size);
 117         if (!src.ptr)
 118                 size = 0;
 119         src.size = size;
 120         dst.ptr = result(entry, &size);
 121         if (!dst.ptr)
 122                 size = 0;
 123         dst.size = size;
 124         if (xdi_diff(&src, &dst, &xpp, &xecfg, &ecb))
 125                 die("unable to generate diff");
 126         free(src.ptr);
 127         free(dst.ptr);
 128 }
 129
 130 static void show_result_list(struct merge_list *entry)
 131 {
 132         printf("%s\n", explanation(entry));
 133         do {
 134                 struct merge_list *link = entry->link;
 135                 static const char *desc[4] = { "result", "base", "our", "their" };
 136                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, oid_to_hex(&entry->blob->object.oid), entry->path);
 137                 entry = link;
 138         } while (entry);
 139 }
 140
 141 static void show_result(void)
 142 {
 143         struct merge_list *walk;
 144
 145         walk = merge_result;
 146         while (walk) {
 147                 show_result_list(walk);
 148                 show_diff(walk);
 149                 walk = walk->next;
 150         }
 151 }
 152
 153 /* An empty entry never compares same, not even to another empty entry */
 154 static int same_entry(struct name_entry *a, struct name_entry *b)
 155 {
 156         return  a->oid &&
 157                 b->oid &&
 158                 !oidcmp(a->oid, b->oid) &&
 159                 a->mode == b->mode;
 160 }
 161
 162 static int both_empty(struct name_entry *a, struct name_entry *b)
 163 {
 164         return !(a->oid || b->oid);
 165 }
 166
 167 static struct merge_list *create_entry(unsigned stage, unsigned mode, const struct object_id *oid, const char *path)
 168 {
 169         struct merge_list *res = xcalloc(1, sizeof(*res));
 170
 171         res->stage = stage;
 172         res->path = path;
 173         res->mode = mode;
 174         res->blob = lookup_blob(the_repository, oid);
 175         return res;
 176 }
 177
 178 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 179 {
 180         char *path = xmallocz(traverse_path_len(info, n));
 181         return make_traverse_path(path, info, n);
 182 }
 183
 184 static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 185 {
 186         struct merge_list *orig, *final;
 187         const char *path;
 188
 189         /* If it's already ours, don't bother showing it */
 190         if (!ours)
 191                 return;
 192
 193         path = traverse_path(info, result);
 194         orig = create_entry(2, ours->mode, ours->oid, path);
 195         final = create_entry(0, result->mode, result->oid, path);
 196
 197         final->link = orig;
 198
 199         add_merge_entry(final);
 200 }
 201
 202 static void unresolved_directory(const struct traverse_info *info,
 203                                  struct name_entry n[3])
 204 {
 205         char *newbase;
 206         struct name_entry *p;
 207         struct tree_desc t[3];
 208         void *buf0, *buf1, *buf2;
 209
 210         for (p = n; p < n + 3; p++) {
 211                 if (p->mode && S_ISDIR(p->mode))
 212                         break;
 213         }
 214         if (n + 3 <= p)
 215                 return; /* there is no tree here */
 216
 217         newbase = traverse_path(info, p);
 218
 219 #define ENTRY_OID(e) (((e)->mode && S_ISDIR((e)->mode)) ? (e)->oid : NULL)
 220         buf0 = fill_tree_descriptor(t + 0, ENTRY_OID(n + 0));
 221         buf1 = fill_tree_descriptor(t + 1, ENTRY_OID(n + 1));
 222         buf2 = fill_tree_descriptor(t + 2, ENTRY_OID(n + 2));
 223 #undef ENTRY_OID
 224
 225         merge_trees(t, newbase);
 226
 227         free(buf0);
 228         free(buf1);
 229         free(buf2);
 230         free(newbase);
 231 }
 232
 233
 234 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 235 {
 236         const char *path;
 237         struct merge_list *link;
 238
 239         if (!n->mode)
 240                 return entry;
 241         if (entry)
 242                 path = entry->path;
 243         else
 244                 path = traverse_path(info, n);
 245         link = create_entry(stage, n->mode, n->oid, path);
 246         link->link = entry;
 247         return link;
 248 }
 249
 250 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 251 {
 252         struct merge_list *entry = NULL;
 253         int i;
 254         unsigned dirmask = 0, mask = 0;
 255
 256         for (i = 0; i < 3; i++) {
 257                 mask |= (1 << i);
 258                 /*
 259                  * Treat missing entries as directories so that we return
 260                  * after unresolved_directory has handled this.
 261                  */
 262                 if (!n[i].mode || S_ISDIR(n[i].mode))
 263                         dirmask |= (1 << i);
 264         }
 265
 266         unresolved_directory(info, n);
 267
 268         if (dirmask == mask)
 269                 return;
 270
 271         if (n[2].mode && !S_ISDIR(n[2].mode))
 272                 entry = link_entry(3, info, n + 2, entry);
 273         if (n[1].mode && !S_ISDIR(n[1].mode))
 274                 entry = link_entry(2, info, n + 1, entry);
 275         if (n[0].mode && !S_ISDIR(n[0].mode))
 276                 entry = link_entry(1, info, n + 0, entry);
 277
 278         add_merge_entry(entry);
 279 }
 280
 281 /*
 282  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 283  * as the origin.
 284  *
 285  * This walks the (sorted) trees in lock-step, checking every possible
 286  * name. Note that directories automatically sort differently from other
 287  * files (see "base_name_compare"), so you'll never see file/directory
 288  * conflicts, because they won't ever compare the same.
 289  *
 290  * IOW, if a directory changes to a filename, it will automatically be
 291  * seen as the directory going away, and the filename being created.
 292  *
 293  * Think of this as a three-way diff.
 294  *
 295  * The output will be either:
 296  *  - successful merge
 297  *       "0 mode sha1 filename"
 298  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 299  *    in parallel with this too!
 300  *
 301  *  - conflict:
 302  *      "1 mode sha1 filename"
 303  *      "2 mode sha1 filename"
 304  *      "3 mode sha1 filename"
 305  *    where not all of the 1/2/3 lines may exist, of course.
 306  *
 307  * The successful merge rules are the same as for the three-way merge
 308  * in git-read-tree.
 309  */
 310 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 311 {
 312         /* Same in both? */
 313         if (same_entry(entry+1, entry+2) || both_empty(entry+1, entry+2)) {
 314                 /* Modified, added or removed identically */
 315                 resolve(info, NULL, entry+1);
 316                 return mask;
 317         }
 318
 319         if (same_entry(entry+0, entry+1)) {
 320                 if (entry[2].oid && !S_ISDIR(entry[2].mode)) {
 321                         /* We did not touch, they modified -- take theirs */
 322                         resolve(info, entry+1, entry+2);
 323                         return mask;
 324                 }
 325                 /*
 326                  * If we did not touch a directory but they made it
 327                  * into a file, we fall through and unresolved()
 328                  * recurses down.  Likewise for the opposite case.
 329                  */
 330         }
 331
 332         if (same_entry(entry+0, entry+2) || both_empty(entry+0, entry+2)) {
 333                 /* We added, modified or removed, they did not touch -- take ours */
 334                 resolve(info, NULL, entry+1);
 335                 return mask;
 336         }
 337
 338         unresolved(info, entry);
 339         return mask;
 340 }
 341
 342 static void merge_trees(struct tree_desc t[3], const char *base)
 343 {
 344         struct traverse_info info;
 345
 346         setup_traverse_info(&info, base);
 347         info.fn = threeway_callback;
 348         traverse_trees(3, t, &info);
 349 }
 350
 351 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 352 {
 353         struct object_id oid;
 354         void *buf;
 355
 356         if (get_oid(rev, &oid))
 357                 die("unknown rev %s", rev);
 358         buf = fill_tree_descriptor(desc, &oid);
 359         if (!buf)
 360                 die("%s is not a tree", rev);
 361         return buf;
 362 }
 363
 364 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 365 {
 366         struct tree_desc t[3];
 367         void *buf1, *buf2, *buf3;
 368
 369         if (argc != 4)
 370                 usage(merge_tree_usage);
 371
 372         buf1 = get_tree_descriptor(t+0, argv[1]);
 373         buf2 = get_tree_descriptor(t+1, argv[2]);
 374         buf3 = get_tree_descriptor(t+2, argv[3]);
 375         merge_trees(t, "");
 376         free(buf1);
 377         free(buf2);
 378         free(buf3);
 379
 380         show_result();
 381         return 0;
 382 }