merge-tree.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3 #include "xdiff-interface.h"
   4 #include "blob.h"
   5
   6 static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   7 static int resolve_directories = 1;
   8
   9 struct merge_list {
  10         struct merge_list *next;
  11         struct merge_list *link;        /* other stages for this object */
  12
  13         unsigned int stage : 2,
  14                      flags : 30;
  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 extern void *merge_file(struct blob *, struct blob *, struct blob *, unsigned long *);
  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
  63         if (!entry->stage)
  64                 return read_sha1_file(entry->blob->object.sha1, &type, size);
  65         base = NULL;
  66         if (entry->stage == 1) {
  67                 base = entry->blob;
  68                 entry = entry->link;
  69         }
  70         our = NULL;
  71         if (entry && entry->stage == 2) {
  72                 our = entry->blob;
  73                 entry = entry->link;
  74         }
  75         their = NULL;
  76         if (entry)
  77                 their = entry->blob;
  78         return merge_file(base, our, their, size);
  79 }
  80
  81 static void *origin(struct merge_list *entry, unsigned long *size)
  82 {
  83         enum object_type type;
  84         while (entry) {
  85                 if (entry->stage == 2)
  86                         return read_sha1_file(entry->blob->object.sha1, &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 = XDF_NEED_MINIMAL;
 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         xdi_diff(&src, &dst, &xpp, &xecfg, &ecb);
 123         free(src.ptr);
 124         free(dst.ptr);
 125 }
 126
 127 static void show_result_list(struct merge_list *entry)
 128 {
 129         printf("%s\n", explanation(entry));
 130         do {
 131                 struct merge_list *link = entry->link;
 132                 static const char *desc[4] = { "result", "base", "our", "their" };
 133                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
 134                 entry = link;
 135         } while (entry);
 136 }
 137
 138 static void show_result(void)
 139 {
 140         struct merge_list *walk;
 141
 142         walk = merge_result;
 143         while (walk) {
 144                 show_result_list(walk);
 145                 show_diff(walk);
 146                 walk = walk->next;
 147         }
 148 }
 149
 150 /* An empty entry never compares same, not even to another empty entry */
 151 static int same_entry(struct name_entry *a, struct name_entry *b)
 152 {
 153         return  a->sha1 &&
 154                 b->sha1 &&
 155                 !hashcmp(a->sha1, b->sha1) &&
 156                 a->mode == b->mode;
 157 }
 158
 159 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 160 {
 161         struct merge_list *res = xcalloc(1, sizeof(*res));
 162
 163         res->stage = stage;
 164         res->path = path;
 165         res->mode = mode;
 166         res->blob = lookup_blob(sha1);
 167         return res;
 168 }
 169
 170 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 171 {
 172         char *path = xmalloc(traverse_path_len(info, n) + 1);
 173         return make_traverse_path(path, info, n);
 174 }
 175
 176 static void resolve(const struct traverse_info *info, struct name_entry *branch1, struct name_entry *result)
 177 {
 178         struct merge_list *orig, *final;
 179         const char *path;
 180
 181         /* If it's already branch1, don't bother showing it */
 182         if (!branch1)
 183                 return;
 184
 185         path = traverse_path(info, result);
 186         orig = create_entry(2, branch1->mode, branch1->sha1, path);
 187         final = create_entry(0, result->mode, result->sha1, path);
 188
 189         final->link = orig;
 190
 191         add_merge_entry(final);
 192 }
 193
 194 static int unresolved_directory(const struct traverse_info *info, struct name_entry n[3])
 195 {
 196         char *newbase;
 197         struct name_entry *p;
 198         struct tree_desc t[3];
 199         void *buf0, *buf1, *buf2;
 200
 201         if (!resolve_directories)
 202                 return 0;
 203         p = n;
 204         if (!p->mode) {
 205                 p++;
 206                 if (!p->mode)
 207                         p++;
 208         }
 209         if (!S_ISDIR(p->mode))
 210                 return 0;
 211         newbase = traverse_path(info, p);
 212         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 213         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 214         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 215         merge_trees(t, newbase);
 216
 217         free(buf0);
 218         free(buf1);
 219         free(buf2);
 220         free(newbase);
 221         return 1;
 222 }
 223
 224
 225 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 226 {
 227         const char *path;
 228         struct merge_list *link;
 229
 230         if (!n->mode)
 231                 return entry;
 232         if (entry)
 233                 path = entry->path;
 234         else
 235                 path = traverse_path(info, n);
 236         link = create_entry(stage, n->mode, n->sha1, path);
 237         link->link = entry;
 238         return link;
 239 }
 240
 241 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 242 {
 243         struct merge_list *entry = NULL;
 244
 245         if (unresolved_directory(info, n))
 246                 return;
 247
 248         /*
 249          * Do them in reverse order so that the resulting link
 250          * list has the stages in order - link_entry adds new
 251          * links at the front.
 252          */
 253         entry = link_entry(3, info, n + 2, entry);
 254         entry = link_entry(2, info, n + 1, entry);
 255         entry = link_entry(1, info, n + 0, entry);
 256
 257         add_merge_entry(entry);
 258 }
 259
 260 /*
 261  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 262  * as the origin.
 263  *
 264  * This walks the (sorted) trees in lock-step, checking every possible
 265  * name. Note that directories automatically sort differently from other
 266  * files (see "base_name_compare"), so you'll never see file/directory
 267  * conflicts, because they won't ever compare the same.
 268  *
 269  * IOW, if a directory changes to a filename, it will automatically be
 270  * seen as the directory going away, and the filename being created.
 271  *
 272  * Think of this as a three-way diff.
 273  *
 274  * The output will be either:
 275  *  - successful merge
 276  *       "0 mode sha1 filename"
 277  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 278  *    in parallel with this too!
 279  *
 280  *  - conflict:
 281  *      "1 mode sha1 filename"
 282  *      "2 mode sha1 filename"
 283  *      "3 mode sha1 filename"
 284  *    where not all of the 1/2/3 lines may exist, of course.
 285  *
 286  * The successful merge rules are the same as for the three-way merge
 287  * in git-read-tree.
 288  */
 289 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 290 {
 291         /* Same in both? */
 292         if (same_entry(entry+1, entry+2)) {
 293                 if (entry[0].sha1) {
 294                         resolve(info, NULL, entry+1);
 295                         return mask;
 296                 }
 297         }
 298
 299         if (same_entry(entry+0, entry+1)) {
 300                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 301                         resolve(info, entry+1, entry+2);
 302                         return mask;
 303                 }
 304         }
 305
 306         if (same_entry(entry+0, entry+2)) {
 307                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 308                         resolve(info, NULL, entry+1);
 309                         return mask;
 310                 }
 311         }
 312
 313         unresolved(info, entry);
 314         return mask;
 315 }
 316
 317 static void merge_trees(struct tree_desc t[3], const char *base)
 318 {
 319         struct traverse_info info;
 320
 321         setup_traverse_info(&info, base);
 322         info.fn = threeway_callback;
 323         traverse_trees(3, t, &info);
 324 }
 325
 326 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 327 {
 328         unsigned char sha1[20];
 329         void *buf;
 330
 331         if (get_sha1(rev, sha1))
 332                 die("unknown rev %s", rev);
 333         buf = fill_tree_descriptor(desc, sha1);
 334         if (!buf)
 335                 die("%s is not a tree", rev);
 336         return buf;
 337 }
 338
 339 int main(int argc, char **argv)
 340 {
 341         struct tree_desc t[3];
 342         void *buf1, *buf2, *buf3;
 343
 344         if (argc != 4)
 345                 usage(merge_tree_usage);
 346
 347         setup_git_directory();
 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 }