match-trees.con commit Merge branch 'sg/clean-nested-repo-with-ignored' (026428c)
   1#include "cache.h"
   2#include "tree.h"
   3#include "tree-walk.h"
   4#include "object-store.h"
   5
   6static int score_missing(unsigned mode)
   7{
   8        int score;
   9
  10        if (S_ISDIR(mode))
  11                score = -1000;
  12        else if (S_ISLNK(mode))
  13                score = -500;
  14        else
  15                score = -50;
  16        return score;
  17}
  18
  19static int score_differs(unsigned mode1, unsigned mode2)
  20{
  21        int score;
  22
  23        if (S_ISDIR(mode1) != S_ISDIR(mode2))
  24                score = -100;
  25        else if (S_ISLNK(mode1) != S_ISLNK(mode2))
  26                score = -50;
  27        else
  28                score = -5;
  29        return score;
  30}
  31
  32static int score_matches(unsigned mode1, unsigned mode2)
  33{
  34        int score;
  35
  36        /* Heh, we found SHA-1 collisions between different kind of objects */
  37        if (S_ISDIR(mode1) != S_ISDIR(mode2))
  38                score = -100;
  39        else if (S_ISLNK(mode1) != S_ISLNK(mode2))
  40                score = -50;
  41
  42        else if (S_ISDIR(mode1))
  43                score = 1000;
  44        else if (S_ISLNK(mode1))
  45                score = 500;
  46        else
  47                score = 250;
  48        return score;
  49}
  50
  51static void *fill_tree_desc_strict(struct tree_desc *desc,
  52                                   const struct object_id *hash)
  53{
  54        void *buffer;
  55        enum object_type type;
  56        unsigned long size;
  57
  58        buffer = read_object_file(hash, &type, &size);
  59        if (!buffer)
  60                die("unable to read tree (%s)", oid_to_hex(hash));
  61        if (type != OBJ_TREE)
  62                die("%s is not a tree", oid_to_hex(hash));
  63        init_tree_desc(desc, buffer, size);
  64        return buffer;
  65}
  66
  67static int base_name_entries_compare(const struct name_entry *a,
  68                                     const struct name_entry *b)
  69{
  70        return base_name_compare(a->path, tree_entry_len(a), a->mode,
  71                                 b->path, tree_entry_len(b), b->mode);
  72}
  73
  74/*
  75 * Inspect two trees, and give a score that tells how similar they are.
  76 */
  77static int score_trees(const struct object_id *hash1, const struct object_id *hash2)
  78{
  79        struct tree_desc one;
  80        struct tree_desc two;
  81        void *one_buf = fill_tree_desc_strict(&one, hash1);
  82        void *two_buf = fill_tree_desc_strict(&two, hash2);
  83        int score = 0;
  84
  85        for (;;) {
  86                int cmp;
  87
  88                if (one.size && two.size)
  89                        cmp = base_name_entries_compare(&one.entry, &two.entry);
  90                else if (one.size)
  91                        /* two lacks this entry */
  92                        cmp = -1;
  93                else if (two.size)
  94                        /* two has more entries */
  95                        cmp = 1;
  96                else
  97                        break;
  98
  99                if (cmp < 0) {
 100                        /* path1 does not appear in two */
 101                        score += score_missing(one.entry.mode);
 102                        update_tree_entry(&one);
 103                } else if (cmp > 0) {
 104                        /* path2 does not appear in one */
 105                        score += score_missing(two.entry.mode);
 106                        update_tree_entry(&two);
 107                } else {
 108                        /* path appears in both */
 109                        if (!oideq(&one.entry.oid, &two.entry.oid)) {
 110                                /* they are different */
 111                                score += score_differs(one.entry.mode,
 112                                                       two.entry.mode);
 113                        } else {
 114                                /* same subtree or blob */
 115                                score += score_matches(one.entry.mode,
 116                                                       two.entry.mode);
 117                        }
 118                        update_tree_entry(&one);
 119                        update_tree_entry(&two);
 120                }
 121        }
 122        free(one_buf);
 123        free(two_buf);
 124        return score;
 125}
 126
 127/*
 128 * Match one itself and its subtrees with two and pick the best match.
 129 */
 130static void match_trees(const struct object_id *hash1,
 131                        const struct object_id *hash2,
 132                        int *best_score,
 133                        char **best_match,
 134                        const char *base,
 135                        int recurse_limit)
 136{
 137        struct tree_desc one;
 138        void *one_buf = fill_tree_desc_strict(&one, hash1);
 139
 140        while (one.size) {
 141                const char *path;
 142                const struct object_id *elem;
 143                unsigned short mode;
 144                int score;
 145
 146                elem = tree_entry_extract(&one, &path, &mode);
 147                if (!S_ISDIR(mode))
 148                        goto next;
 149                score = score_trees(elem, hash2);
 150                if (*best_score < score) {
 151                        free(*best_match);
 152                        *best_match = xstrfmt("%s%s", base, path);
 153                        *best_score = score;
 154                }
 155                if (recurse_limit) {
 156                        char *newbase = xstrfmt("%s%s/", base, path);
 157                        match_trees(elem, hash2, best_score, best_match,
 158                                    newbase, recurse_limit - 1);
 159                        free(newbase);
 160                }
 161
 162        next:
 163                update_tree_entry(&one);
 164        }
 165        free(one_buf);
 166}
 167
 168/*
 169 * A tree "oid1" has a subdirectory at "prefix".  Come up with a tree object by
 170 * replacing it with another tree "oid2".
 171 */
 172static int splice_tree(const struct object_id *oid1, const char *prefix,
 173                       const struct object_id *oid2, struct object_id *result)
 174{
 175        char *subpath;
 176        int toplen;
 177        char *buf;
 178        unsigned long sz;
 179        struct tree_desc desc;
 180        unsigned char *rewrite_here;
 181        const struct object_id *rewrite_with;
 182        struct object_id subtree;
 183        enum object_type type;
 184        int status;
 185
 186        subpath = strchrnul(prefix, '/');
 187        toplen = subpath - prefix;
 188        if (*subpath)
 189                subpath++;
 190
 191        buf = read_object_file(oid1, &type, &sz);
 192        if (!buf)
 193                die("cannot read tree %s", oid_to_hex(oid1));
 194        init_tree_desc(&desc, buf, sz);
 195
 196        rewrite_here = NULL;
 197        while (desc.size) {
 198                const char *name;
 199                unsigned short mode;
 200
 201                tree_entry_extract(&desc, &name, &mode);
 202                if (strlen(name) == toplen &&
 203                    !memcmp(name, prefix, toplen)) {
 204                        if (!S_ISDIR(mode))
 205                                die("entry %s in tree %s is not a tree", name,
 206                                    oid_to_hex(oid1));
 207
 208                        /*
 209                         * We cast here for two reasons:
 210                         *
 211                         *   - to flip the "char *" (for the path) to "unsigned
 212                         *     char *" (for the hash stored after it)
 213                         *
 214                         *   - to discard the "const"; this is OK because we
 215                         *     know it points into our non-const "buf"
 216                         */
 217                        rewrite_here = (unsigned char *)(desc.entry.path +
 218                                                         strlen(desc.entry.path) +
 219                                                         1);
 220                        break;
 221                }
 222                update_tree_entry(&desc);
 223        }
 224        if (!rewrite_here)
 225                die("entry %.*s not found in tree %s", toplen, prefix,
 226                    oid_to_hex(oid1));
 227        if (*subpath) {
 228                struct object_id tree_oid;
 229                hashcpy(tree_oid.hash, rewrite_here);
 230                status = splice_tree(&tree_oid, subpath, oid2, &subtree);
 231                if (status)
 232                        return status;
 233                rewrite_with = &subtree;
 234        } else {
 235                rewrite_with = oid2;
 236        }
 237        hashcpy(rewrite_here, rewrite_with->hash);
 238        status = write_object_file(buf, sz, tree_type, result);
 239        free(buf);
 240        return status;
 241}
 242
 243/*
 244 * We are trying to come up with a merge between one and two that
 245 * results in a tree shape similar to one.  The tree two might
 246 * correspond to a subtree of one, in which case it needs to be
 247 * shifted down by prefixing otherwise empty directories.  On the
 248 * other hand, it could cover tree one and we might need to pick a
 249 * subtree of it.
 250 */
 251void shift_tree(struct repository *r,
 252                const struct object_id *hash1,
 253                const struct object_id *hash2,
 254                struct object_id *shifted,
 255                int depth_limit)
 256{
 257        char *add_prefix;
 258        char *del_prefix;
 259        int add_score, del_score;
 260
 261        /*
 262         * NEEDSWORK: this limits the recursion depth to hardcoded
 263         * value '2' to avoid excessive overhead.
 264         */
 265        if (!depth_limit)
 266                depth_limit = 2;
 267
 268        add_score = del_score = score_trees(hash1, hash2);
 269        add_prefix = xcalloc(1, 1);
 270        del_prefix = xcalloc(1, 1);
 271
 272        /*
 273         * See if one's subtree resembles two; if so we need to prefix
 274         * two with a few fake trees to match the prefix.
 275         */
 276        match_trees(hash1, hash2, &add_score, &add_prefix, "", depth_limit);
 277
 278        /*
 279         * See if two's subtree resembles one; if so we need to
 280         * pick only subtree of two.
 281         */
 282        match_trees(hash2, hash1, &del_score, &del_prefix, "", depth_limit);
 283
 284        /* Assume we do not have to do any shifting */
 285        oidcpy(shifted, hash2);
 286
 287        if (add_score < del_score) {
 288                /* We need to pick a subtree of two */
 289                unsigned short mode;
 290
 291                if (!*del_prefix)
 292                        return;
 293
 294                if (get_tree_entry(r, hash2, del_prefix, shifted, &mode))
 295                        die("cannot find path %s in tree %s",
 296                            del_prefix, oid_to_hex(hash2));
 297                return;
 298        }
 299
 300        if (!*add_prefix)
 301                return;
 302
 303        splice_tree(hash1, add_prefix, hash2, shifted);
 304}
 305
 306/*
 307 * The user says the trees will be shifted by this much.
 308 * Unfortunately we cannot fundamentally tell which one to
 309 * be prefixed, as recursive merge can work in either direction.
 310 */
 311void shift_tree_by(struct repository *r,
 312                   const struct object_id *hash1,
 313                   const struct object_id *hash2,
 314                   struct object_id *shifted,
 315                   const char *shift_prefix)
 316{
 317        struct object_id sub1, sub2;
 318        unsigned short mode1, mode2;
 319        unsigned candidate = 0;
 320
 321        /* Can hash2 be a tree at shift_prefix in tree hash1? */
 322        if (!get_tree_entry(r, hash1, shift_prefix, &sub1, &mode1) &&
 323            S_ISDIR(mode1))
 324                candidate |= 1;
 325
 326        /* Can hash1 be a tree at shift_prefix in tree hash2? */
 327        if (!get_tree_entry(r, hash2, shift_prefix, &sub2, &mode2) &&
 328            S_ISDIR(mode2))
 329                candidate |= 2;
 330
 331        if (candidate == 3) {
 332                /* Both are plausible -- we need to evaluate the score */
 333                int best_score = score_trees(hash1, hash2);
 334                int score;
 335
 336                candidate = 0;
 337                score = score_trees(&sub1, hash2);
 338                if (score > best_score) {
 339                        candidate = 1;
 340                        best_score = score;
 341                }
 342                score = score_trees(&sub2, hash1);
 343                if (score > best_score)
 344                        candidate = 2;
 345        }
 346
 347        if (!candidate) {
 348                /* Neither is plausible -- do not shift */
 349                oidcpy(shifted, hash2);
 350                return;
 351        }
 352
 353        if (candidate == 1)
 354                /*
 355                 * shift tree2 down by adding shift_prefix above it
 356                 * to match tree1.
 357                 */
 358                splice_tree(hash1, shift_prefix, hash2, shifted);
 359        else
 360                /*
 361                 * shift tree2 up by removing shift_prefix from it
 362                 * to match tree1.
 363                 */
 364                oidcpy(shifted, &sub2);
 365}