merge-tree.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3 #include "blob.h"
   4
   5 static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   6 static int resolve_directories = 1;
   7
   8 struct merge_list {
   9         struct merge_list *next;
  10         struct merge_list *link;        /* other stages for this object */
  11
  12         unsigned int stage : 2,
  13                      flags : 30;
  14         unsigned int mode;
  15         const char *path;
  16         struct blob *blob;
  17 };
  18
  19 static struct merge_list *merge_result, **merge_result_end = &merge_result;
  20
  21 static void add_merge_entry(struct merge_list *entry)
  22 {
  23         *merge_result_end = entry;
  24         merge_result_end = &entry->next;
  25 }
  26
  27 static void merge_trees(struct tree_desc t[3], const char *base);
  28
  29 static const char *explanation(struct merge_list *entry)
  30 {
  31         switch (entry->stage) {
  32         case 0:
  33                 return "merged";
  34         case 3:
  35                 return "added in remote";
  36         case 2:
  37                 if (entry->link)
  38                         return "added in both";
  39                 return "added in local";
  40         }
  41
  42         /* Existed in base */
  43         entry = entry->link;
  44         if (!entry)
  45                 return "removed in both";
  46
  47         if (entry->link)
  48                 return "changed in both";
  49
  50         if (entry->stage == 3)
  51                 return "removed in local";
  52         return "removed in remote";
  53 }
  54
  55 static void show_result_list(struct merge_list *entry)
  56 {
  57         printf("%s\n", explanation(entry));
  58         do {
  59                 struct merge_list *link = entry->link;
  60                 static const char *desc[4] = { "result", "base", "our", "their" };
  61                 printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
  62                 entry = link;
  63         } while (entry);
  64 }
  65
  66 static void show_result(void)
  67 {
  68         struct merge_list *walk;
  69
  70         walk = merge_result;
  71         while (walk) {
  72                 show_result_list(walk);
  73                 walk = walk->next;
  74         }
  75 }
  76
  77 /* An empty entry never compares same, not even to another empty entry */
  78 static int same_entry(struct name_entry *a, struct name_entry *b)
  79 {
  80         return  a->sha1 &&
  81                 b->sha1 &&
  82                 !memcmp(a->sha1, b->sha1, 20) &&
  83                 a->mode == b->mode;
  84 }
  85
  86 static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
  87 {
  88         struct merge_list *res = xmalloc(sizeof(*res));
  89
  90         memset(res, 0, sizeof(*res));
  91         res->stage = stage;
  92         res->path = path;
  93         res->mode = mode;
  94         res->blob = lookup_blob(sha1);
  95         return res;
  96 }
  97
  98 static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
  99 {
 100         struct merge_list *orig, *final;
 101         const char *path;
 102
 103         /* If it's already branch1, don't bother showing it */
 104         if (!branch1)
 105                 return;
 106
 107         path = strdup(mkpath("%s%s", base, result->path));
 108         orig = create_entry(2, branch1->mode, branch1->sha1, path);
 109         final = create_entry(0, result->mode, result->sha1, path);
 110
 111         final->link = orig;
 112
 113         add_merge_entry(final);
 114 }
 115
 116 static int unresolved_directory(const char *base, struct name_entry n[3])
 117 {
 118         int baselen;
 119         char *newbase;
 120         struct name_entry *p;
 121         struct tree_desc t[3];
 122         void *buf0, *buf1, *buf2;
 123
 124         if (!resolve_directories)
 125                 return 0;
 126         p = n;
 127         if (!p->mode) {
 128                 p++;
 129                 if (!p->mode)
 130                         p++;
 131         }
 132         if (!S_ISDIR(p->mode))
 133                 return 0;
 134         baselen = strlen(base);
 135         newbase = xmalloc(baselen + p->pathlen + 2);
 136         memcpy(newbase, base, baselen);
 137         memcpy(newbase + baselen, p->path, p->pathlen);
 138         memcpy(newbase + baselen + p->pathlen, "/", 2);
 139
 140         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 141         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 142         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 143         merge_trees(t, newbase);
 144
 145         free(buf0);
 146         free(buf1);
 147         free(buf2);
 148         free(newbase);
 149         return 1;
 150 }
 151
 152
 153 static struct merge_list *link_entry(unsigned stage, const char *base, struct name_entry *n, struct merge_list *entry)
 154 {
 155         const char *path;
 156         struct merge_list *link;
 157
 158         if (!n->mode)
 159                 return entry;
 160         if (entry)
 161                 path = entry->path;
 162         else
 163                 path = strdup(mkpath("%s%s", base, n->path));
 164         link = create_entry(stage, n->mode, n->sha1, path);
 165         link->link = entry;
 166         return link;
 167 }
 168
 169 static void unresolved(const char *base, struct name_entry n[3])
 170 {
 171         struct merge_list *entry = NULL;
 172
 173         if (unresolved_directory(base, n))
 174                 return;
 175
 176         /*
 177          * Do them in reverse order so that the resulting link
 178          * list has the stages in order - link_entry adds new
 179          * links at the front.
 180          */
 181         entry = link_entry(3, base, n + 2, entry);
 182         entry = link_entry(2, base, n + 1, entry);
 183         entry = link_entry(1, base, n + 0, entry);
 184
 185         add_merge_entry(entry);
 186 }
 187
 188 /*
 189  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 190  * as the origin.
 191  *
 192  * This walks the (sorted) trees in lock-step, checking every possible
 193  * name. Note that directories automatically sort differently from other
 194  * files (see "base_name_compare"), so you'll never see file/directory
 195  * conflicts, because they won't ever compare the same.
 196  *
 197  * IOW, if a directory changes to a filename, it will automatically be
 198  * seen as the directory going away, and the filename being created.
 199  *
 200  * Think of this as a three-way diff.
 201  *
 202  * The output will be either:
 203  *  - successful merge
 204  *       "0 mode sha1 filename"
 205  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 206  *    in parallel with this too!
 207  *
 208  *  - conflict:
 209  *      "1 mode sha1 filename"
 210  *      "2 mode sha1 filename"
 211  *      "3 mode sha1 filename"
 212  *    where not all of the 1/2/3 lines may exist, of course.
 213  *
 214  * The successful merge rules are the same as for the three-way merge
 215  * in git-read-tree.
 216  */
 217 static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
 218 {
 219         /* Same in both? */
 220         if (same_entry(entry+1, entry+2)) {
 221                 if (entry[0].sha1) {
 222                         resolve(base, NULL, entry+1);
 223                         return;
 224                 }
 225         }
 226
 227         if (same_entry(entry+0, entry+1)) {
 228                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 229                         resolve(base, entry+1, entry+2);
 230                         return;
 231                 }
 232         }
 233
 234         if (same_entry(entry+0, entry+2)) {
 235                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 236                         resolve(base, NULL, entry+1);
 237                         return;
 238                 }
 239         }
 240
 241         unresolved(base, entry);
 242 }
 243
 244 static void merge_trees(struct tree_desc t[3], const char *base)
 245 {
 246         traverse_trees(3, t, base, threeway_callback);
 247 }
 248
 249 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 250 {
 251         unsigned char sha1[20];
 252         void *buf;
 253
 254         if (get_sha1(rev, sha1))
 255                 die("unknown rev %s", rev);
 256         buf = fill_tree_descriptor(desc, sha1);
 257         if (!buf)
 258                 die("%s is not a tree", rev);
 259         return buf;
 260 }
 261
 262 int main(int argc, char **argv)
 263 {
 264         struct tree_desc t[3];
 265         void *buf1, *buf2, *buf3;
 266
 267         if (argc < 4)
 268                 usage(merge_tree_usage);
 269
 270         buf1 = get_tree_descriptor(t+0, argv[1]);
 271         buf2 = get_tree_descriptor(t+1, argv[2]);
 272         buf3 = get_tree_descriptor(t+2, argv[3]);
 273         merge_trees(t, "");
 274         free(buf1);
 275         free(buf2);
 276         free(buf3);
 277
 278         show_result();
 279         return 0;
 280 }