merge-tree.con commit Merge branches 'jc/rev-list' and 'jc/pack-thin' (f0b0af1)
   1#include "cache.h"
   2#include "diff.h"
   3
   4static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   5static int resolve_directories = 1;
   6
   7static void merge_trees(struct tree_desc t[3], const char *base);
   8
   9static void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
  10{
  11        unsigned long size = 0;
  12        void *buf = NULL;
  13
  14        if (sha1) {
  15                buf = read_object_with_reference(sha1, "tree", &size, NULL);
  16                if (!buf)
  17                        die("unable to read tree %s", sha1_to_hex(sha1));
  18        }
  19        desc->size = size;
  20        desc->buf = buf;
  21        return buf;
  22}
  23
  24struct name_entry {
  25        const unsigned char *sha1;
  26        const char *path;
  27        unsigned int mode;
  28        int pathlen;
  29};
  30
  31static void entry_clear(struct name_entry *a)
  32{
  33        memset(a, 0, sizeof(*a));
  34}
  35
  36static int entry_compare(struct name_entry *a, struct name_entry *b)
  37{
  38        return base_name_compare(
  39                        a->path, a->pathlen, a->mode,
  40                        b->path, b->pathlen, b->mode);
  41}
  42
  43static void entry_extract(struct tree_desc *t, struct name_entry *a)
  44{
  45        a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
  46        a->pathlen = strlen(a->path);
  47}
  48
  49/* An empty entry never compares same, not even to another empty entry */
  50static int same_entry(struct name_entry *a, struct name_entry *b)
  51{
  52        return  a->sha1 &&
  53                b->sha1 &&
  54                !memcmp(a->sha1, b->sha1, 20) &&
  55                a->mode == b->mode;
  56}
  57
  58static const char *sha1_to_hex_zero(const unsigned char *sha1)
  59{
  60        if (sha1)
  61                return sha1_to_hex(sha1);
  62        return "0000000000000000000000000000000000000000";
  63}
  64
  65static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
  66{
  67        char branch1_sha1[50];
  68
  69        /* If it's already branch1, don't bother showing it */
  70        if (!branch1)
  71                return;
  72        memcpy(branch1_sha1, sha1_to_hex_zero(branch1->sha1), 41);
  73
  74        printf("0 %06o->%06o %s->%s %s%s\n",
  75                branch1->mode, result->mode,
  76                branch1_sha1, sha1_to_hex_zero(result->sha1),
  77                base, result->path);
  78}
  79
  80static int unresolved_directory(const char *base, struct name_entry n[3])
  81{
  82        int baselen;
  83        char *newbase;
  84        struct name_entry *p;
  85        struct tree_desc t[3];
  86        void *buf0, *buf1, *buf2;
  87
  88        if (!resolve_directories)
  89                return 0;
  90        p = n;
  91        if (!p->mode) {
  92                p++;
  93                if (!p->mode)
  94                        p++;
  95        }
  96        if (!S_ISDIR(p->mode))
  97                return 0;
  98        baselen = strlen(base);
  99        newbase = xmalloc(baselen + p->pathlen + 2);
 100        memcpy(newbase, base, baselen);
 101        memcpy(newbase + baselen, p->path, p->pathlen);
 102        memcpy(newbase + baselen + p->pathlen, "/", 2);
 103
 104        buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 105        buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 106        buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 107        merge_trees(t, newbase);
 108
 109        free(buf0);
 110        free(buf1);
 111        free(buf2);
 112        free(newbase);
 113        return 1;
 114}
 115
 116static void unresolved(const char *base, struct name_entry n[3])
 117{
 118        if (unresolved_directory(base, n))
 119                return;
 120        if (n[0].sha1)
 121                printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path);
 122        if (n[1].sha1)
 123                printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path);
 124        if (n[2].sha1)
 125                printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
 126}
 127
 128typedef void (*traverse_callback_t)(int n, unsigned long mask, struct name_entry *entry, const char *base);
 129
 130static void traverse_trees(int n, struct tree_desc *t, const char *base, traverse_callback_t callback)
 131{
 132        struct name_entry *entry = xmalloc(n*sizeof(*entry));
 133
 134        for (;;) {
 135                struct name_entry entry[3];
 136                unsigned long mask = 0;
 137                int i, last;
 138
 139                last = -1;
 140                for (i = 0; i < n; i++) {
 141                        if (!t[i].size)
 142                                continue;
 143                        entry_extract(t+i, entry+i);
 144                        if (last >= 0) {
 145                                int cmp = entry_compare(entry+i, entry+last);
 146
 147                                /*
 148                                 * Is the new name bigger than the old one?
 149                                 * Ignore it
 150                                 */
 151                                if (cmp > 0)
 152                                        continue;
 153                                /*
 154                                 * Is the new name smaller than the old one?
 155                                 * Ignore all old ones
 156                                 */
 157                                if (cmp < 0)
 158                                        mask = 0;
 159                        }
 160                        mask |= 1ul << i;
 161                        last = i;
 162                }
 163                if (!mask)
 164                        break;
 165
 166                /*
 167                 * Update the tree entries we've walked, and clear
 168                 * all the unused name-entries.
 169                 */
 170                for (i = 0; i < n; i++) {
 171                        if (mask & (1ul << i)) {
 172                                update_tree_entry(t+i);
 173                                continue;
 174                        }
 175                        entry_clear(entry + i);
 176                }
 177                callback(n, mask, entry, base);
 178        }
 179        free(entry);
 180}
 181
 182/*
 183 * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 184 * as the origin.
 185 *
 186 * This walks the (sorted) trees in lock-step, checking every possible
 187 * name. Note that directories automatically sort differently from other
 188 * files (see "base_name_compare"), so you'll never see file/directory
 189 * conflicts, because they won't ever compare the same.
 190 *
 191 * IOW, if a directory changes to a filename, it will automatically be
 192 * seen as the directory going away, and the filename being created.
 193 *
 194 * Think of this as a three-way diff.
 195 *
 196 * The output will be either:
 197 *  - successful merge
 198 *       "0 mode sha1 filename"
 199 *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 200 *    in parallel with this too!
 201 *
 202 *  - conflict:
 203 *      "1 mode sha1 filename"
 204 *      "2 mode sha1 filename"
 205 *      "3 mode sha1 filename"
 206 *    where not all of the 1/2/3 lines may exist, of course.
 207 *
 208 * The successful merge rules are the same as for the three-way merge
 209 * in git-read-tree.
 210 */
 211static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
 212{
 213        /* Same in both? */
 214        if (same_entry(entry+1, entry+2)) {
 215                if (entry[0].sha1) {
 216                        resolve(base, NULL, entry+1);
 217                        return;
 218                }
 219        }
 220
 221        if (same_entry(entry+0, entry+1)) {
 222                if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 223                        resolve(base, entry+1, entry+2);
 224                        return;
 225                }
 226        }
 227
 228        if (same_entry(entry+0, entry+2)) {
 229                if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 230                        resolve(base, NULL, entry+1);
 231                        return;
 232                }
 233        }
 234
 235        unresolved(base, entry);
 236}
 237
 238static void merge_trees(struct tree_desc t[3], const char *base)
 239{
 240        traverse_trees(3, t, base, threeway_callback);
 241}
 242
 243static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 244{
 245        unsigned char sha1[20];
 246        void *buf;
 247
 248        if (get_sha1(rev, sha1) < 0)
 249                die("unknown rev %s", rev);
 250        buf = fill_tree_descriptor(desc, sha1);
 251        if (!buf)
 252                die("%s is not a tree", rev);
 253        return buf;
 254}
 255
 256int main(int argc, char **argv)
 257{
 258        struct tree_desc t[3];
 259        void *buf1, *buf2, *buf3;
 260
 261        if (argc < 4)
 262                usage(merge_tree_usage);
 263
 264        buf1 = get_tree_descriptor(t+0, argv[1]);
 265        buf2 = get_tree_descriptor(t+1, argv[2]);
 266        buf3 = get_tree_descriptor(t+2, argv[3]);
 267        merge_trees(t, "");
 268        free(buf1);
 269        free(buf2);
 270        free(buf3);
 271        return 0;
 272}