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 struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 159 {
 160         struct merge_list *res = xcalloc(1, sizeof(*res));
 161
 162         res->stage = stage;
 163         res->path = path;
 164         res->mode = mode;
 165         res->blob = lookup_blob(sha1);
 166         return res;
 167 }
 168
 169 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 170 {
 171         char *path = xmalloc(traverse_path_len(info, n) + 1);
 172         return make_traverse_path(path, info, n);
 173 }
 174
 175 static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 176 {
 177         struct merge_list *orig, *final;
 178         const char *path;
 179
 180         /* If it's already ours, don't bother showing it */
 181         if (!ours)
 182                 return;
 183
 184         path = traverse_path(info, result);
 185         orig = create_entry(2, ours->mode, ours->sha1, path);
 186         final = create_entry(0, result->mode, result->sha1, path);
 187
 188         final->link = orig;
 189
 190         add_merge_entry(final);
 191 }
 192
 193 static int unresolved_directory(const struct traverse_info *info, struct name_entry n[3])
 194 {
 195         char *newbase;
 196         struct name_entry *p;
 197         struct tree_desc t[3];
 198         void *buf0, *buf1, *buf2;
 199
 200         p = n;
 201         if (!p->mode) {
 202                 p++;
 203                 if (!p->mode)
 204                         p++;
 205         }
 206         if (!S_ISDIR(p->mode))
 207                 return 0;
 208         /*
 209          * NEEDSWORK: this is broken. The path can originally be a file
 210          * and then one side may have turned it into a directory, in which
 211          * case we return and let the three-way merge as if the tree were
 212          * a regular file.  If the path that was originally a tree is
 213          * now a file in either branch, fill_tree_descriptor() below will
 214          * die when fed a blob sha1.
 215          */
 216
 217         newbase = traverse_path(info, p);
 218         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 219         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 220         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 221         merge_trees(t, newbase);
 222
 223         free(buf0);
 224         free(buf1);
 225         free(buf2);
 226         free(newbase);
 227         return 1;
 228 }
 229
 230
 231 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 232 {
 233         const char *path;
 234         struct merge_list *link;
 235
 236         if (!n->mode)
 237                 return entry;
 238         if (entry)
 239                 path = entry->path;
 240         else
 241                 path = traverse_path(info, n);
 242         link = create_entry(stage, n->mode, n->sha1, path);
 243         link->link = entry;
 244         return link;
 245 }
 246
 247 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 248 {
 249         struct merge_list *entry = NULL;
 250
 251         if (unresolved_directory(info, n))
 252                 return;
 253
 254         /*
 255          * Do them in reverse order so that the resulting link
 256          * list has the stages in order - link_entry adds new
 257          * links at the front.
 258          */
 259         entry = link_entry(3, info, n + 2, entry);
 260         entry = link_entry(2, info, n + 1, entry);
 261         entry = link_entry(1, info, n + 0, entry);
 262
 263         add_merge_entry(entry);
 264 }
 265
 266 /*
 267  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 268  * as the origin.
 269  *
 270  * This walks the (sorted) trees in lock-step, checking every possible
 271  * name. Note that directories automatically sort differently from other
 272  * files (see "base_name_compare"), so you'll never see file/directory
 273  * conflicts, because they won't ever compare the same.
 274  *
 275  * IOW, if a directory changes to a filename, it will automatically be
 276  * seen as the directory going away, and the filename being created.
 277  *
 278  * Think of this as a three-way diff.
 279  *
 280  * The output will be either:
 281  *  - successful merge
 282  *       "0 mode sha1 filename"
 283  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 284  *    in parallel with this too!
 285  *
 286  *  - conflict:
 287  *      "1 mode sha1 filename"
 288  *      "2 mode sha1 filename"
 289  *      "3 mode sha1 filename"
 290  *    where not all of the 1/2/3 lines may exist, of course.
 291  *
 292  * The successful merge rules are the same as for the three-way merge
 293  * in git-read-tree.
 294  */
 295 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 296 {
 297         /* Same in both? */
 298         if (same_entry(entry+1, entry+2)) {
 299                 if (entry[0].sha1) {
 300                         /* Modified identically */
 301                         resolve(info, NULL, entry+1);
 302                         return mask;
 303                 }
 304                 /* "Both added the same" is left unresolved */
 305         }
 306
 307         if (same_entry(entry+0, entry+1)) {
 308                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 309                         /* We did not touch, they modified -- take theirs */
 310                         resolve(info, entry+1, entry+2);
 311                         return mask;
 312                 }
 313                 /*
 314                  * If we did not touch a directory but they made it
 315                  * into a file, we fall through and unresolved()
 316                  * recurses down.  Likewise for the opposite case.
 317                  */
 318         }
 319
 320         if (same_entry(entry+0, entry+2)) {
 321                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 322                         /* We modified, they did not touch -- take ours */
 323                         resolve(info, NULL, entry+1);
 324                         return mask;
 325                 }
 326         }
 327
 328         unresolved(info, entry);
 329         return mask;
 330 }
 331
 332 static void merge_trees(struct tree_desc t[3], const char *base)
 333 {
 334         struct traverse_info info;
 335
 336         setup_traverse_info(&info, base);
 337         info.fn = threeway_callback;
 338         traverse_trees(3, t, &info);
 339 }
 340
 341 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 342 {
 343         unsigned char sha1[20];
 344         void *buf;
 345
 346         if (get_sha1(rev, sha1))
 347                 die("unknown rev %s", rev);
 348         buf = fill_tree_descriptor(desc, sha1);
 349         if (!buf)
 350                 die("%s is not a tree", rev);
 351         return buf;
 352 }
 353
 354 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 355 {
 356         struct tree_desc t[3];
 357         void *buf1, *buf2, *buf3;
 358
 359         if (argc != 4)
 360                 usage(merge_tree_usage);
 361
 362         buf1 = get_tree_descriptor(t+0, argv[1]);
 363         buf2 = get_tree_descriptor(t+1, argv[2]);
 364         buf3 = get_tree_descriptor(t+2, argv[3]);
 365         merge_trees(t, "");
 366         free(buf1);
 367         free(buf2);
 368         free(buf3);
 369
 370         show_result();
 371         return 0;
 372 }