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_sha1_file(entry->blob->object.sha1, &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_sha1_file(entry->blob->object.sha1, &type, size);
  86                 entry = entry->link;
  87         }
  88         return NULL;
  89 }
  90
  91 static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  92 {
  93         int i;
  94         for (i = 0; i < nbuf; i++)
  95                 printf("%.*s", (int) mb[i].size, mb[i].ptr);
  96         return 0;
  97 }
  98
  99 static void show_diff(struct merge_list *entry)
 100 {
 101         unsigned long size;
 102         mmfile_t src, dst;
 103         xpparam_t xpp;
 104         xdemitconf_t xecfg;
 105         xdemitcb_t ecb;
 106
 107         xpp.flags = 0;
 108         memset(&xecfg, 0, sizeof(xecfg));
 109         xecfg.ctxlen = 3;
 110         ecb.outf = show_outf;
 111         ecb.priv = NULL;
 112
 113         src.ptr = origin(entry, &size);
 114         if (!src.ptr)
 115                 size = 0;
 116         src.size = size;
 117         dst.ptr = result(entry, &size);
 118         if (!dst.ptr)
 119                 size = 0;
 120         dst.size = size;
 121         xdi_diff(&src, &dst, &xpp, &xecfg, &ecb);
 122         free(src.ptr);
 123         free(dst.ptr);
 124 }
 125
 126 static void show_result_list(struct merge_list *entry)
 127 {
 128         printf("%s\n", explanation(entry));
 129         do {
 130                 struct merge_list *link = entry->link;
 131                 static const char *desc[4] = { "result", "base", "our", "their" };
 132                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
 133                 entry = link;
 134         } while (entry);
 135 }
 136
 137 static void show_result(void)
 138 {
 139         struct merge_list *walk;
 140
 141         walk = merge_result;
 142         while (walk) {
 143                 show_result_list(walk);
 144                 show_diff(walk);
 145                 walk = walk->next;
 146         }
 147 }
 148
 149 /* An empty entry never compares same, not even to another empty entry */
 150 static int same_entry(struct name_entry *a, struct name_entry *b)
 151 {
 152         return  a->sha1 &&
 153                 b->sha1 &&
 154                 !hashcmp(a->sha1, b->sha1) &&
 155                 a->mode == b->mode;
 156 }
 157
 158 static int both_empty(struct name_entry *a, struct name_entry *b)
 159 {
 160         return !(a->sha1 || b->sha1);
 161 }
 162
 163 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 164 {
 165         struct merge_list *res = xcalloc(1, sizeof(*res));
 166
 167         res->stage = stage;
 168         res->path = path;
 169         res->mode = mode;
 170         res->blob = lookup_blob(sha1);
 171         return res;
 172 }
 173
 174 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 175 {
 176         char *path = xmalloc(traverse_path_len(info, n) + 1);
 177         return make_traverse_path(path, info, n);
 178 }
 179
 180 static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 181 {
 182         struct merge_list *orig, *final;
 183         const char *path;
 184
 185         /* If it's already ours, don't bother showing it */
 186         if (!ours)
 187                 return;
 188
 189         path = traverse_path(info, result);
 190         orig = create_entry(2, ours->mode, ours->sha1, path);
 191         final = create_entry(0, result->mode, result->sha1, path);
 192
 193         final->link = orig;
 194
 195         add_merge_entry(final);
 196 }
 197
 198 static void unresolved_directory(const struct traverse_info *info,
 199                                  struct name_entry n[3])
 200 {
 201         char *newbase;
 202         struct name_entry *p;
 203         struct tree_desc t[3];
 204         void *buf0, *buf1, *buf2;
 205
 206         for (p = n; p < n + 3; p++) {
 207                 if (p->mode && S_ISDIR(p->mode))
 208                         break;
 209         }
 210         if (n + 3 <= p)
 211                 return; /* there is no tree here */
 212
 213         newbase = traverse_path(info, p);
 214
 215 #define ENTRY_SHA1(e) (((e)->mode && S_ISDIR((e)->mode)) ? (e)->sha1 : NULL)
 216         buf0 = fill_tree_descriptor(t+0, ENTRY_SHA1(n + 0));
 217         buf1 = fill_tree_descriptor(t+1, ENTRY_SHA1(n + 1));
 218         buf2 = fill_tree_descriptor(t+2, ENTRY_SHA1(n + 2));
 219 #undef ENTRY_SHA1
 220
 221         merge_trees(t, newbase);
 222
 223         free(buf0);
 224         free(buf1);
 225         free(buf2);
 226         free(newbase);
 227 }
 228
 229
 230 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 231 {
 232         const char *path;
 233         struct merge_list *link;
 234
 235         if (!n->mode)
 236                 return entry;
 237         if (entry)
 238                 path = entry->path;
 239         else
 240                 path = traverse_path(info, n);
 241         link = create_entry(stage, n->mode, n->sha1, path);
 242         link->link = entry;
 243         return link;
 244 }
 245
 246 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 247 {
 248         struct merge_list *entry = NULL;
 249         int i;
 250         unsigned dirmask = 0, mask = 0;
 251
 252         for (i = 0; i < 3; i++) {
 253                 mask |= (1 << i);
 254                 /*
 255                  * Treat missing entries as directories so that we return
 256                  * after unresolved_directory has handled this.
 257                  */
 258                 if (!n[i].mode || S_ISDIR(n[i].mode))
 259                         dirmask |= (1 << i);
 260         }
 261
 262         unresolved_directory(info, n);
 263
 264         if (dirmask == mask)
 265                 return;
 266
 267         if (n[2].mode && !S_ISDIR(n[2].mode))
 268                 entry = link_entry(3, info, n + 2, entry);
 269         if (n[1].mode && !S_ISDIR(n[1].mode))
 270                 entry = link_entry(2, info, n + 1, entry);
 271         if (n[0].mode && !S_ISDIR(n[0].mode))
 272                 entry = link_entry(1, info, n + 0, entry);
 273
 274         add_merge_entry(entry);
 275 }
 276
 277 /*
 278  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 279  * as the origin.
 280  *
 281  * This walks the (sorted) trees in lock-step, checking every possible
 282  * name. Note that directories automatically sort differently from other
 283  * files (see "base_name_compare"), so you'll never see file/directory
 284  * conflicts, because they won't ever compare the same.
 285  *
 286  * IOW, if a directory changes to a filename, it will automatically be
 287  * seen as the directory going away, and the filename being created.
 288  *
 289  * Think of this as a three-way diff.
 290  *
 291  * The output will be either:
 292  *  - successful merge
 293  *       "0 mode sha1 filename"
 294  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 295  *    in parallel with this too!
 296  *
 297  *  - conflict:
 298  *      "1 mode sha1 filename"
 299  *      "2 mode sha1 filename"
 300  *      "3 mode sha1 filename"
 301  *    where not all of the 1/2/3 lines may exist, of course.
 302  *
 303  * The successful merge rules are the same as for the three-way merge
 304  * in git-read-tree.
 305  */
 306 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 307 {
 308         /* Same in both? */
 309         if (same_entry(entry+1, entry+2) || both_empty(entry+1, entry+2)) {
 310                 /* Modified, added or removed identically */
 311                 resolve(info, NULL, entry+1);
 312                 return mask;
 313         }
 314
 315         if (same_entry(entry+0, entry+1)) {
 316                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 317                         /* We did not touch, they modified -- take theirs */
 318                         resolve(info, entry+1, entry+2);
 319                         return mask;
 320                 }
 321                 /*
 322                  * If we did not touch a directory but they made it
 323                  * into a file, we fall through and unresolved()
 324                  * recurses down.  Likewise for the opposite case.
 325                  */
 326         }
 327
 328         if (same_entry(entry+0, entry+2) || both_empty(entry+0, entry+2)) {
 329                 /* We added, modified or removed, they did not touch -- take ours */
 330                 resolve(info, NULL, entry+1);
 331                 return mask;
 332         }
 333
 334         unresolved(info, entry);
 335         return mask;
 336 }
 337
 338 static void merge_trees(struct tree_desc t[3], const char *base)
 339 {
 340         struct traverse_info info;
 341
 342         setup_traverse_info(&info, base);
 343         info.fn = threeway_callback;
 344         traverse_trees(3, t, &info);
 345 }
 346
 347 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 348 {
 349         unsigned char sha1[20];
 350         void *buf;
 351
 352         if (get_sha1(rev, sha1))
 353                 die("unknown rev %s", rev);
 354         buf = fill_tree_descriptor(desc, sha1);
 355         if (!buf)
 356                 die("%s is not a tree", rev);
 357         return buf;
 358 }
 359
 360 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 361 {
 362         struct tree_desc t[3];
 363         void *buf1, *buf2, *buf3;
 364
 365         if (argc != 4)
 366                 usage(merge_tree_usage);
 367
 368         buf1 = get_tree_descriptor(t+0, argv[1]);
 369         buf2 = get_tree_descriptor(t+1, argv[2]);
 370         buf3 = get_tree_descriptor(t+2, argv[3]);
 371         merge_trees(t, "");
 372         free(buf1);
 373         free(buf2);
 374         free(buf3);
 375
 376         show_result();
 377         return 0;
 378 }