builtin/merge-tree.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3 #include "xdiff-interface.h"
   4 #include "blob.h"
   5 #include "exec_cmd.h"
   6
   7 static const char merge_tree_usage[] = "git merge-tree <base-tree> <branch1> <branch2>";
   8 static int resolve_directories = 1;
   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                      flags : 30;
  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 extern void *merge_file(const char *, struct blob *, struct blob *, struct blob *, unsigned long *);
  58
  59 static void *result(struct merge_list *entry, unsigned long *size)
  60 {
  61         enum object_type type;
  62         struct blob *base, *our, *their;
  63         const char *path = entry->path;
  64
  65         if (!entry->stage)
  66                 return read_sha1_file(entry->blob->object.sha1, &type, size);
  67         base = NULL;
  68         if (entry->stage == 1) {
  69                 base = entry->blob;
  70                 entry = entry->link;
  71         }
  72         our = NULL;
  73         if (entry && entry->stage == 2) {
  74                 our = entry->blob;
  75                 entry = entry->link;
  76         }
  77         their = NULL;
  78         if (entry)
  79                 their = entry->blob;
  80         return merge_file(path, base, our, their, size);
  81 }
  82
  83 static void *origin(struct merge_list *entry, unsigned long *size)
  84 {
  85         enum object_type type;
  86         while (entry) {
  87                 if (entry->stage == 2)
  88                         return read_sha1_file(entry->blob->object.sha1, &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         xdi_diff(&src, &dst, &xpp, &xecfg, &ecb);
 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, sha1_to_hex(entry->blob->object.sha1), 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->sha1 &&
 156                 b->sha1 &&
 157                 !hashcmp(a->sha1, b->sha1) &&
 158                 a->mode == b->mode;
 159 }
 160
 161 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 162 {
 163         struct merge_list *res = xcalloc(1, sizeof(*res));
 164
 165         res->stage = stage;
 166         res->path = path;
 167         res->mode = mode;
 168         res->blob = lookup_blob(sha1);
 169         return res;
 170 }
 171
 172 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 173 {
 174         char *path = xmalloc(traverse_path_len(info, n) + 1);
 175         return make_traverse_path(path, info, n);
 176 }
 177
 178 static void resolve(const struct traverse_info *info, struct name_entry *branch1, struct name_entry *result)
 179 {
 180         struct merge_list *orig, *final;
 181         const char *path;
 182
 183         /* If it's already branch1, don't bother showing it */
 184         if (!branch1)
 185                 return;
 186
 187         path = traverse_path(info, result);
 188         orig = create_entry(2, branch1->mode, branch1->sha1, path);
 189         final = create_entry(0, result->mode, result->sha1, path);
 190
 191         final->link = orig;
 192
 193         add_merge_entry(final);
 194 }
 195
 196 static int unresolved_directory(const struct traverse_info *info, struct name_entry n[3])
 197 {
 198         char *newbase;
 199         struct name_entry *p;
 200         struct tree_desc t[3];
 201         void *buf0, *buf1, *buf2;
 202
 203         if (!resolve_directories)
 204                 return 0;
 205         p = n;
 206         if (!p->mode) {
 207                 p++;
 208                 if (!p->mode)
 209                         p++;
 210         }
 211         if (!S_ISDIR(p->mode))
 212                 return 0;
 213         newbase = traverse_path(info, p);
 214         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 215         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 216         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 217         merge_trees(t, newbase);
 218
 219         free(buf0);
 220         free(buf1);
 221         free(buf2);
 222         free(newbase);
 223         return 1;
 224 }
 225
 226
 227 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 228 {
 229         const char *path;
 230         struct merge_list *link;
 231
 232         if (!n->mode)
 233                 return entry;
 234         if (entry)
 235                 path = entry->path;
 236         else
 237                 path = traverse_path(info, n);
 238         link = create_entry(stage, n->mode, n->sha1, path);
 239         link->link = entry;
 240         return link;
 241 }
 242
 243 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 244 {
 245         struct merge_list *entry = NULL;
 246
 247         if (unresolved_directory(info, n))
 248                 return;
 249
 250         /*
 251          * Do them in reverse order so that the resulting link
 252          * list has the stages in order - link_entry adds new
 253          * links at the front.
 254          */
 255         entry = link_entry(3, info, n + 2, entry);
 256         entry = link_entry(2, info, n + 1, entry);
 257         entry = link_entry(1, info, n + 0, entry);
 258
 259         add_merge_entry(entry);
 260 }
 261
 262 /*
 263  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 264  * as the origin.
 265  *
 266  * This walks the (sorted) trees in lock-step, checking every possible
 267  * name. Note that directories automatically sort differently from other
 268  * files (see "base_name_compare"), so you'll never see file/directory
 269  * conflicts, because they won't ever compare the same.
 270  *
 271  * IOW, if a directory changes to a filename, it will automatically be
 272  * seen as the directory going away, and the filename being created.
 273  *
 274  * Think of this as a three-way diff.
 275  *
 276  * The output will be either:
 277  *  - successful merge
 278  *       "0 mode sha1 filename"
 279  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 280  *    in parallel with this too!
 281  *
 282  *  - conflict:
 283  *      "1 mode sha1 filename"
 284  *      "2 mode sha1 filename"
 285  *      "3 mode sha1 filename"
 286  *    where not all of the 1/2/3 lines may exist, of course.
 287  *
 288  * The successful merge rules are the same as for the three-way merge
 289  * in git-read-tree.
 290  */
 291 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 292 {
 293         /* Same in both? */
 294         if (same_entry(entry+1, entry+2)) {
 295                 if (entry[0].sha1) {
 296                         resolve(info, NULL, entry+1);
 297                         return mask;
 298                 }
 299         }
 300
 301         if (same_entry(entry+0, entry+1)) {
 302                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 303                         resolve(info, entry+1, entry+2);
 304                         return mask;
 305                 }
 306         }
 307
 308         if (same_entry(entry+0, entry+2)) {
 309                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 310                         resolve(info, NULL, entry+1);
 311                         return mask;
 312                 }
 313         }
 314
 315         unresolved(info, entry);
 316         return mask;
 317 }
 318
 319 static void merge_trees(struct tree_desc t[3], const char *base)
 320 {
 321         struct traverse_info info;
 322
 323         setup_traverse_info(&info, base);
 324         info.fn = threeway_callback;
 325         traverse_trees(3, t, &info);
 326 }
 327
 328 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 329 {
 330         unsigned char sha1[20];
 331         void *buf;
 332
 333         if (get_sha1(rev, sha1))
 334                 die("unknown rev %s", rev);
 335         buf = fill_tree_descriptor(desc, sha1);
 336         if (!buf)
 337                 die("%s is not a tree", rev);
 338         return buf;
 339 }
 340
 341 int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 342 {
 343         struct tree_desc t[3];
 344         void *buf1, *buf2, *buf3;
 345
 346         if (argc != 4)
 347                 usage(merge_tree_usage);
 348
 349         buf1 = get_tree_descriptor(t+0, argv[1]);
 350         buf2 = get_tree_descriptor(t+1, argv[2]);
 351         buf3 = get_tree_descriptor(t+2, argv[3]);
 352         merge_trees(t, "");
 353         free(buf1);
 354         free(buf2);
 355         free(buf3);
 356
 357         show_result();
 358         return 0;
 359 }