5704d51050d3de27a5ffadde9931179ad3fa713d
   1#include "builtin.h"
   2#include "tree-walk.h"
   3#include "xdiff-interface.h"
   4#include "blob.h"
   5#include "exec_cmd.h"
   6#include "merge-blobs.h"
   7
   8static const char merge_tree_usage[] = "git merge-tree <base-tree> <branch1> <branch2>";
   9
  10struct merge_list {
  11        struct merge_list *next;
  12        struct merge_list *link;        /* other stages for this object */
  13
  14        unsigned int stage : 2;
  15        unsigned int mode;
  16        const char *path;
  17        struct blob *blob;
  18};
  19
  20static struct merge_list *merge_result, **merge_result_end = &merge_result;
  21
  22static void add_merge_entry(struct merge_list *entry)
  23{
  24        *merge_result_end = entry;
  25        merge_result_end = &entry->next;
  26}
  27
  28static void merge_trees(struct tree_desc t[3], const char *base);
  29
  30static 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
  56static void *result(struct merge_list *entry, unsigned long *size)
  57{
  58        enum object_type type;
  59        struct blob *base, *our, *their;
  60        const char *path = entry->path;
  61
  62        if (!entry->stage)
  63                return read_sha1_file(entry->blob->object.sha1, &type, size);
  64        base = NULL;
  65        if (entry->stage == 1) {
  66                base = entry->blob;
  67                entry = entry->link;
  68        }
  69        our = NULL;
  70        if (entry && entry->stage == 2) {
  71                our = entry->blob;
  72                entry = entry->link;
  73        }
  74        their = NULL;
  75        if (entry)
  76                their = entry->blob;
  77        return merge_blobs(path, base, our, their, size);
  78}
  79
  80static void *origin(struct merge_list *entry, unsigned long *size)
  81{
  82        enum object_type type;
  83        while (entry) {
  84                if (entry->stage == 2)
  85                        return read_sha1_file(entry->blob->object.sha1, &type, size);
  86                entry = entry->link;
  87        }
  88        return NULL;
  89}
  90
  91static int show_outf(void *priv_, mmbuffer_t *mb, int nbuf)
  92{
  93        int i;
  94        for (i = 0; i < nbuf; i++)
  95                printf("%.*s", (int) mb[i].size, mb[i].ptr);
  96        return 0;
  97}
  98
  99static void show_diff(struct merge_list *entry)
 100{
 101        unsigned long size;
 102        mmfile_t src, dst;
 103        xpparam_t xpp;
 104        xdemitconf_t xecfg;
 105        xdemitcb_t ecb;
 106
 107        xpp.flags = 0;
 108        memset(&xecfg, 0, sizeof(xecfg));
 109        xecfg.ctxlen = 3;
 110        ecb.outf = show_outf;
 111        ecb.priv = NULL;
 112
 113        src.ptr = origin(entry, &size);
 114        if (!src.ptr)
 115                size = 0;
 116        src.size = size;
 117        dst.ptr = result(entry, &size);
 118        if (!dst.ptr)
 119                size = 0;
 120        dst.size = size;
 121        xdi_diff(&src, &dst, &xpp, &xecfg, &ecb);
 122        free(src.ptr);
 123        free(dst.ptr);
 124}
 125
 126static void show_result_list(struct merge_list *entry)
 127{
 128        printf("%s\n", explanation(entry));
 129        do {
 130                struct merge_list *link = entry->link;
 131                static const char *desc[4] = { "result", "base", "our", "their" };
 132                printf("  %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
 133                entry = link;
 134        } while (entry);
 135}
 136
 137static void show_result(void)
 138{
 139        struct merge_list *walk;
 140
 141        walk = merge_result;
 142        while (walk) {
 143                show_result_list(walk);
 144                show_diff(walk);
 145                walk = walk->next;
 146        }
 147}
 148
 149/* An empty entry never compares same, not even to another empty entry */
 150static int same_entry(struct name_entry *a, struct name_entry *b)
 151{
 152        return  a->sha1 &&
 153                b->sha1 &&
 154                !hashcmp(a->sha1, b->sha1) &&
 155                a->mode == b->mode;
 156}
 157
 158static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
 159{
 160        struct merge_list *res = xcalloc(1, sizeof(*res));
 161
 162        res->stage = stage;
 163        res->path = path;
 164        res->mode = mode;
 165        res->blob = lookup_blob(sha1);
 166        return res;
 167}
 168
 169static char *traverse_path(const struct traverse_info *info, const struct name_entry *n)
 170{
 171        char *path = xmalloc(traverse_path_len(info, n) + 1);
 172        return make_traverse_path(path, info, n);
 173}
 174
 175static void resolve(const struct traverse_info *info, struct name_entry *ours, struct name_entry *result)
 176{
 177        struct merge_list *orig, *final;
 178        const char *path;
 179
 180        /* If it's already ours, don't bother showing it */
 181        if (!ours)
 182                return;
 183
 184        path = traverse_path(info, result);
 185        orig = create_entry(2, ours->mode, ours->sha1, path);
 186        final = create_entry(0, result->mode, result->sha1, path);
 187
 188        final->link = orig;
 189
 190        add_merge_entry(final);
 191}
 192
 193static int unresolved_directory(const struct traverse_info *info, struct name_entry n[3])
 194{
 195        char *newbase;
 196        struct name_entry *p;
 197        struct tree_desc t[3];
 198        void *buf0, *buf1, *buf2;
 199
 200        p = n;
 201        if (!p->mode) {
 202                p++;
 203                if (!p->mode)
 204                        p++;
 205        }
 206        if (!S_ISDIR(p->mode))
 207                return 0;
 208        /*
 209         * NEEDSWORK: this is broken. The path can originally be a file
 210         * and then one side may have turned it into a directory, in which
 211         * case we return and let the three-way merge as if the tree were
 212         * a regular file.  If the path that was originally a tree is
 213         * now a file in either branch, fill_tree_descriptor() below will
 214         * die when fed a blob sha1.
 215         */
 216
 217        newbase = traverse_path(info, p);
 218        buf0 = fill_tree_descriptor(t+0, n[0].sha1);
 219        buf1 = fill_tree_descriptor(t+1, n[1].sha1);
 220        buf2 = fill_tree_descriptor(t+2, n[2].sha1);
 221        merge_trees(t, newbase);
 222
 223        free(buf0);
 224        free(buf1);
 225        free(buf2);
 226        free(newbase);
 227        return 1;
 228}
 229
 230
 231static struct merge_list *link_entry(unsigned stage, const struct traverse_info *info, struct name_entry *n, struct merge_list *entry)
 232{
 233        const char *path;
 234        struct merge_list *link;
 235
 236        if (!n->mode)
 237                return entry;
 238        if (entry)
 239                path = entry->path;
 240        else
 241                path = traverse_path(info, n);
 242        link = create_entry(stage, n->mode, n->sha1, path);
 243        link->link = entry;
 244        return link;
 245}
 246
 247static void unresolved(const struct traverse_info *info, struct name_entry n[3])
 248{
 249        struct merge_list *entry = NULL;
 250
 251        if (unresolved_directory(info, n))
 252                return;
 253
 254        /*
 255         * Do them in reverse order so that the resulting link
 256         * list has the stages in order - link_entry adds new
 257         * links at the front.
 258         */
 259        entry = link_entry(3, info, n + 2, entry);
 260        entry = link_entry(2, info, n + 1, entry);
 261        entry = link_entry(1, info, n + 0, entry);
 262
 263        add_merge_entry(entry);
 264}
 265
 266/*
 267 * Merge two trees together (t[1] and t[2]), using a common base (t[0])
 268 * as the origin.
 269 *
 270 * This walks the (sorted) trees in lock-step, checking every possible
 271 * name. Note that directories automatically sort differently from other
 272 * files (see "base_name_compare"), so you'll never see file/directory
 273 * conflicts, because they won't ever compare the same.
 274 *
 275 * IOW, if a directory changes to a filename, it will automatically be
 276 * seen as the directory going away, and the filename being created.
 277 *
 278 * Think of this as a three-way diff.
 279 *
 280 * The output will be either:
 281 *  - successful merge
 282 *       "0 mode sha1 filename"
 283 *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 284 *    in parallel with this too!
 285 *
 286 *  - conflict:
 287 *      "1 mode sha1 filename"
 288 *      "2 mode sha1 filename"
 289 *      "3 mode sha1 filename"
 290 *    where not all of the 1/2/3 lines may exist, of course.
 291 *
 292 * The successful merge rules are the same as for the three-way merge
 293 * in git-read-tree.
 294 */
 295static int threeway_callback(int n, unsigned long mask, unsigned long dirmask, struct name_entry *entry, struct traverse_info *info)
 296{
 297        /* Same in both? */
 298        if (same_entry(entry+1, entry+2)) {
 299                if (entry[0].sha1) {
 300                        /* Modified identically */
 301                        resolve(info, NULL, entry+1);
 302                        return mask;
 303                }
 304                /* "Both added the same" is left unresolved */
 305        }
 306
 307        if (same_entry(entry+0, entry+1)) {
 308                if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 309                        /* We did not touch, they modified -- take theirs */
 310                        resolve(info, entry+1, entry+2);
 311                        return mask;
 312                }
 313                /*
 314                 * If we did not touch a directory but they made it
 315                 * into a file, we fall through and unresolved()
 316                 * recurses down.  Likewise for the opposite case.
 317                 */
 318        }
 319
 320        if (same_entry(entry+0, entry+2)) {
 321                if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 322                        /* We modified, they did not touch -- take ours */
 323                        resolve(info, NULL, entry+1);
 324                        return mask;
 325                }
 326        }
 327
 328        unresolved(info, entry);
 329        return mask;
 330}
 331
 332static void merge_trees(struct tree_desc t[3], const char *base)
 333{
 334        struct traverse_info info;
 335
 336        setup_traverse_info(&info, base);
 337        info.fn = threeway_callback;
 338        traverse_trees(3, t, &info);
 339}
 340
 341static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 342{
 343        unsigned char sha1[20];
 344        void *buf;
 345
 346        if (get_sha1(rev, sha1))
 347                die("unknown rev %s", rev);
 348        buf = fill_tree_descriptor(desc, sha1);
 349        if (!buf)
 350                die("%s is not a tree", rev);
 351        return buf;
 352}
 353
 354int cmd_merge_tree(int argc, const char **argv, const char *prefix)
 355{
 356        struct tree_desc t[3];
 357        void *buf1, *buf2, *buf3;
 358
 359        if (argc != 4)
 360                usage(merge_tree_usage);
 361
 362        buf1 = get_tree_descriptor(t+0, argv[1]);
 363        buf2 = get_tree_descriptor(t+1, argv[2]);
 364        buf3 = get_tree_descriptor(t+2, argv[3]);
 365        merge_trees(t, "");
 366        free(buf1);
 367        free(buf2);
 368        free(buf3);
 369
 370        show_result();
 371        return 0;
 372}