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(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
  64         if (!entry->stage)
  65                 return read_sha1_file(entry->blob->object.sha1, &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_file(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_sha1_file(entry->blob->object.sha1, &type, size);
  88                 entry = entry->link;
  89         }
  90         return NULL;
  91 }
  92
  93 static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  94 {
  95         int i;
  96         for (i = 0; i < nbuf; i++)
  97                 printf("%.*s", (int) mb[i].size, mb[i].ptr);
  98         return 0;
  99 }
 100
 101 static void show_diff(struct merge_list *entry)
 102 {
 103         unsigned long size;
 104         mmfile_t src, dst;
 105         xpparam_t xpp;
 106         xdemitconf_t xecfg;
 107         xdemitcb_t ecb;
 108
 109         xpp.flags = XDF_NEED_MINIMAL;
 110         memset(&xecfg, 0, sizeof(xecfg));
 111         xecfg.ctxlen = 3;
 112         ecb.outf = show_outf;
 113         ecb.priv = NULL;
 114
 115         src.ptr = origin(entry, &size);
 116         if (!src.ptr)
 117                 size = 0;
 118         src.size = size;
 119         dst.ptr = result(entry, &size);
 120         if (!dst.ptr)
 121                 size = 0;
 122         dst.size = size;
 123         xdi_diff(&src, &dst, &xpp, &xecfg, &ecb);
 124         free(src.ptr);
 125         free(dst.ptr);
 126 }
 127
 128 static void show_result_list(struct merge_list *entry)
 129 {
 130         printf("%s\n", explanation(entry));
 131         do {
 132                 struct merge_list *link = entry->link;
 133                 static const char *desc[4] = { "result", "base", "our", "their" };
 134                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
 135                 entry = link;
 136         } while (entry);
 137 }
 138
 139 static void show_result(void)
 140 {
 141         struct merge_list *walk;
 142
 143         walk = merge_result;
 144         while (walk) {
 145                 show_result_list(walk);
 146                 show_diff(walk);
 147                 walk = walk->next;
 148         }
 149 }
 150
 151 /* An empty entry never compares same, not even to another empty entry */
 152 static int same_entry(struct name_entry *a, struct name_entry *b)
 153 {
 154         return  a->sha1 &&
 155                 b->sha1 &&
 156                 !hashcmp(a->sha1, b->sha1) &&
 157                 a->mode == b->mode;
 158 }
 159
 160 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 161 {
 162         struct merge_list *res = xcalloc(1, sizeof(*res));
 163
 164         res->stage = stage;
 165         res->path = path;
 166         res->mode = mode;
 167         res->blob = lookup_blob(sha1);
 168         return res;
 169 }
 170
 171 static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 172 {
 173         char *path = xmalloc(traverse_path_len(info, n) + 1);
 174         return make_traverse_path(path, info, n);
 175 }
 176
 177 static void resolve(const struct traverse_info *info, struct name_entry *branch1, struct name_entry *result)
 178 {
 179         struct merge_list *orig, *final;
 180         const char *path;
 181
 182         /* If it's already branch1, don't bother showing it */
 183         if (!branch1)
 184                 return;
 185
 186         path = traverse_path(info, result);
 187         orig = create_entry(2, branch1->mode, branch1->sha1, path);
 188         final = create_entry(0, result->mode, result->sha1, path);
 189
 190         final->link = orig;
 191
 192         add_merge_entry(final);
 193 }
 194
 195 static int unresolved_directory(const struct traverse_info *info, struct name_entry n[3])
 196 {
 197         char *newbase;
 198         struct name_entry *p;
 199         struct tree_desc t[3];
 200         void *buf0, *buf1, *buf2;
 201
 202         if (!resolve_directories)
 203                 return 0;
 204         p = n;
 205         if (!p->mode) {
 206                 p++;
 207                 if (!p->mode)
 208                         p++;
 209         }
 210         if (!S_ISDIR(p->mode))
 211                 return 0;
 212         newbase = traverse_path(info, p);
 213         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 214         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 215         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 216         merge_trees(t, newbase);
 217
 218         free(buf0);
 219         free(buf1);
 220         free(buf2);
 221         free(newbase);
 222         return 1;
 223 }
 224
 225
 226 static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 227 {
 228         const char *path;
 229         struct merge_list *link;
 230
 231         if (!n->mode)
 232                 return entry;
 233         if (entry)
 234                 path = entry->path;
 235         else
 236                 path = traverse_path(info, n);
 237         link = create_entry(stage, n->mode, n->sha1, path);
 238         link->link = entry;
 239         return link;
 240 }
 241
 242 static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 243 {
 244         struct merge_list *entry = NULL;
 245
 246         if (unresolved_directory(info, n))
 247                 return;
 248
 249         /*
 250          * Do them in reverse order so that the resulting link
 251          * list has the stages in order - link_entry adds new
 252          * links at the front.
 253          */
 254         entry = link_entry(3, info, n + 2, entry);
 255         entry = link_entry(2, info, n + 1, entry);
 256         entry = link_entry(1, info, n + 0, entry);
 257
 258         add_merge_entry(entry);
 259 }
 260
 261 /*
 262  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 263  * as the origin.
 264  *
 265  * This walks the (sorted) trees in lock-step, checking every possible
 266  * name. Note that directories automatically sort differently from other
 267  * files (see "base_name_compare"), so you'll never see file/directory
 268  * conflicts, because they won't ever compare the same.
 269  *
 270  * IOW, if a directory changes to a filename, it will automatically be
 271  * seen as the directory going away, and the filename being created.
 272  *
 273  * Think of this as a three-way diff.
 274  *
 275  * The output will be either:
 276  *  - successful merge
 277  *       "0 mode sha1 filename"
 278  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 279  *    in parallel with this too!
 280  *
 281  *  - conflict:
 282  *      "1 mode sha1 filename"
 283  *      "2 mode sha1 filename"
 284  *      "3 mode sha1 filename"
 285  *    where not all of the 1/2/3 lines may exist, of course.
 286  *
 287  * The successful merge rules are the same as for the three-way merge
 288  * in git-read-tree.
 289  */
 290 static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 291 {
 292         /* Same in both? */
 293         if (same_entry(entry+1, entry+2)) {
 294                 if (entry[0].sha1) {
 295                         resolve(info, NULL, entry+1);
 296                         return mask;
 297                 }
 298         }
 299
 300         if (same_entry(entry+0, entry+1)) {
 301                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 302                         resolve(info, entry+1, entry+2);
 303                         return mask;
 304                 }
 305         }
 306
 307         if (same_entry(entry+0, entry+2)) {
 308                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 309                         resolve(info, NULL, entry+1);
 310                         return mask;
 311                 }
 312         }
 313
 314         unresolved(info, entry);
 315         return mask;
 316 }
 317
 318 static void merge_trees(struct tree_desc t[3], const char *base)
 319 {
 320         struct traverse_info info;
 321
 322         setup_traverse_info(&info, base);
 323         info.fn = threeway_callback;
 324         traverse_trees(3, t, &info);
 325 }
 326
 327 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 328 {
 329         unsigned char sha1[20];
 330         void *buf;
 331
 332         if (get_sha1(rev, sha1))
 333                 die("unknown rev %s", rev);
 334         buf = fill_tree_descriptor(desc, sha1);
 335         if (!buf)
 336                 die("%s is not a tree", rev);
 337         return buf;
 338 }
 339
 340 int main(int argc, char **argv)
 341 {
 342         struct tree_desc t[3];
 343         void *buf1, *buf2, *buf3;
 344
 345         if (argc != 4)
 346                 usage(merge_tree_usage);
 347
 348         git_extract_argv0_path(argv[0]);
 349
 350         setup_git_directory();
 351
 352         buf1 = get_tree_descriptor(t+0, argv[1]);
 353         buf2 = get_tree_descriptor(t+1, argv[2]);
 354         buf3 = get_tree_descriptor(t+2, argv[3]);
 355         merge_trees(t, "");
 356         free(buf1);
 357         free(buf2);
 358         free(buf3);
 359
 360         show_result();
 361         return 0;
 362 }