notes.con commit Merge branch 'jc/mention-tracking-for-pull-default' into maint (cd9c038)
   1#include "cache.h"
   2#include "notes.h"
   3#include "blob.h"
   4#include "tree.h"
   5#include "utf8.h"
   6#include "strbuf.h"
   7#include "tree-walk.h"
   8#include "string-list.h"
   9#include "refs.h"
  10
  11/*
  12 * Use a non-balancing simple 16-tree structure with struct int_node as
  13 * internal nodes, and struct leaf_node as leaf nodes. Each int_node has a
  14 * 16-array of pointers to its children.
  15 * The bottom 2 bits of each pointer is used to identify the pointer type
  16 * - ptr & 3 == 0 - NULL pointer, assert(ptr == NULL)
  17 * - ptr & 3 == 1 - pointer to next internal node - cast to struct int_node *
  18 * - ptr & 3 == 2 - pointer to note entry - cast to struct leaf_node *
  19 * - ptr & 3 == 3 - pointer to subtree entry - cast to struct leaf_node *
  20 *
  21 * The root node is a statically allocated struct int_node.
  22 */
  23struct int_node {
  24        void *a[16];
  25};
  26
  27/*
  28 * Leaf nodes come in two variants, note entries and subtree entries,
  29 * distinguished by the LSb of the leaf node pointer (see above).
  30 * As a note entry, the key is the SHA1 of the referenced object, and the
  31 * value is the SHA1 of the note object.
  32 * As a subtree entry, the key is the prefix SHA1 (w/trailing NULs) of the
  33 * referenced object, using the last byte of the key to store the length of
  34 * the prefix. The value is the SHA1 of the tree object containing the notes
  35 * subtree.
  36 */
  37struct leaf_node {
  38        unsigned char key_sha1[20];
  39        unsigned char val_sha1[20];
  40};
  41
  42/*
  43 * A notes tree may contain entries that are not notes, and that do not follow
  44 * the naming conventions of notes. There are typically none/few of these, but
  45 * we still need to keep track of them. Keep a simple linked list sorted alpha-
  46 * betically on the non-note path. The list is populated when parsing tree
  47 * objects in load_subtree(), and the non-notes are correctly written back into
  48 * the tree objects produced by write_notes_tree().
  49 */
  50struct non_note {
  51        struct non_note *next; /* grounded (last->next == NULL) */
  52        char *path;
  53        unsigned int mode;
  54        unsigned char sha1[20];
  55};
  56
  57#define PTR_TYPE_NULL     0
  58#define PTR_TYPE_INTERNAL 1
  59#define PTR_TYPE_NOTE     2
  60#define PTR_TYPE_SUBTREE  3
  61
  62#define GET_PTR_TYPE(ptr)       ((uintptr_t) (ptr) & 3)
  63#define CLR_PTR_TYPE(ptr)       ((void *) ((uintptr_t) (ptr) & ~3))
  64#define SET_PTR_TYPE(ptr, type) ((void *) ((uintptr_t) (ptr) | (type)))
  65
  66#define GET_NIBBLE(n, sha1) (((sha1[(n) >> 1]) >> ((~(n) & 0x01) << 2)) & 0x0f)
  67
  68#define SUBTREE_SHA1_PREFIXCMP(key_sha1, subtree_sha1) \
  69        (memcmp(key_sha1, subtree_sha1, subtree_sha1[19]))
  70
  71struct notes_tree default_notes_tree;
  72
  73static struct string_list display_notes_refs;
  74static struct notes_tree **display_notes_trees;
  75
  76static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
  77                struct int_node *node, unsigned int n);
  78
  79/*
  80 * Search the tree until the appropriate location for the given key is found:
  81 * 1. Start at the root node, with n = 0
  82 * 2. If a[0] at the current level is a matching subtree entry, unpack that
  83 *    subtree entry and remove it; restart search at the current level.
  84 * 3. Use the nth nibble of the key as an index into a:
  85 *    - If a[n] is an int_node, recurse from #2 into that node and increment n
  86 *    - If a matching subtree entry, unpack that subtree entry (and remove it);
  87 *      restart search at the current level.
  88 *    - Otherwise, we have found one of the following:
  89 *      - a subtree entry which does not match the key
  90 *      - a note entry which may or may not match the key
  91 *      - an unused leaf node (NULL)
  92 *      In any case, set *tree and *n, and return pointer to the tree location.
  93 */
  94static void **note_tree_search(struct notes_tree *t, struct int_node **tree,
  95                unsigned char *n, const unsigned char *key_sha1)
  96{
  97        struct leaf_node *l;
  98        unsigned char i;
  99        void *p = (*tree)->a[0];
 100
 101        if (GET_PTR_TYPE(p) == PTR_TYPE_SUBTREE) {
 102                l = (struct leaf_node *) CLR_PTR_TYPE(p);
 103                if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
 104                        /* unpack tree and resume search */
 105                        (*tree)->a[0] = NULL;
 106                        load_subtree(t, l, *tree, *n);
 107                        free(l);
 108                        return note_tree_search(t, tree, n, key_sha1);
 109                }
 110        }
 111
 112        i = GET_NIBBLE(*n, key_sha1);
 113        p = (*tree)->a[i];
 114        switch (GET_PTR_TYPE(p)) {
 115        case PTR_TYPE_INTERNAL:
 116                *tree = CLR_PTR_TYPE(p);
 117                (*n)++;
 118                return note_tree_search(t, tree, n, key_sha1);
 119        case PTR_TYPE_SUBTREE:
 120                l = (struct leaf_node *) CLR_PTR_TYPE(p);
 121                if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
 122                        /* unpack tree and resume search */
 123                        (*tree)->a[i] = NULL;
 124                        load_subtree(t, l, *tree, *n);
 125                        free(l);
 126                        return note_tree_search(t, tree, n, key_sha1);
 127                }
 128                /* fall through */
 129        default:
 130                return &((*tree)->a[i]);
 131        }
 132}
 133
 134/*
 135 * To find a leaf_node:
 136 * Search to the tree location appropriate for the given key:
 137 * If a note entry with matching key, return the note entry, else return NULL.
 138 */
 139static struct leaf_node *note_tree_find(struct notes_tree *t,
 140                struct int_node *tree, unsigned char n,
 141                const unsigned char *key_sha1)
 142{
 143        void **p = note_tree_search(t, &tree, &n, key_sha1);
 144        if (GET_PTR_TYPE(*p) == PTR_TYPE_NOTE) {
 145                struct leaf_node *l = (struct leaf_node *) CLR_PTR_TYPE(*p);
 146                if (!hashcmp(key_sha1, l->key_sha1))
 147                        return l;
 148        }
 149        return NULL;
 150}
 151
 152/*
 153 * How to consolidate an int_node:
 154 * If there are > 1 non-NULL entries, give up and return non-zero.
 155 * Otherwise replace the int_node at the given index in the given parent node
 156 * with the only entry (or a NULL entry if no entries) from the given tree,
 157 * and return 0.
 158 */
 159static int note_tree_consolidate(struct int_node *tree,
 160        struct int_node *parent, unsigned char index)
 161{
 162        unsigned int i;
 163        void *p = NULL;
 164
 165        assert(tree && parent);
 166        assert(CLR_PTR_TYPE(parent->a[index]) == tree);
 167
 168        for (i = 0; i < 16; i++) {
 169                if (GET_PTR_TYPE(tree->a[i]) != PTR_TYPE_NULL) {
 170                        if (p) /* more than one entry */
 171                                return -2;
 172                        p = tree->a[i];
 173                }
 174        }
 175
 176        /* replace tree with p in parent[index] */
 177        parent->a[index] = p;
 178        free(tree);
 179        return 0;
 180}
 181
 182/*
 183 * To remove a leaf_node:
 184 * Search to the tree location appropriate for the given leaf_node's key:
 185 * - If location does not hold a matching entry, abort and do nothing.
 186 * - Copy the matching entry's value into the given entry.
 187 * - Replace the matching leaf_node with a NULL entry (and free the leaf_node).
 188 * - Consolidate int_nodes repeatedly, while walking up the tree towards root.
 189 */
 190static void note_tree_remove(struct notes_tree *t,
 191                struct int_node *tree, unsigned char n,
 192                struct leaf_node *entry)
 193{
 194        struct leaf_node *l;
 195        struct int_node *parent_stack[20];
 196        unsigned char i, j;
 197        void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
 198
 199        assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
 200        if (GET_PTR_TYPE(*p) != PTR_TYPE_NOTE)
 201                return; /* type mismatch, nothing to remove */
 202        l = (struct leaf_node *) CLR_PTR_TYPE(*p);
 203        if (hashcmp(l->key_sha1, entry->key_sha1))
 204                return; /* key mismatch, nothing to remove */
 205
 206        /* we have found a matching entry */
 207        hashcpy(entry->val_sha1, l->val_sha1);
 208        free(l);
 209        *p = SET_PTR_TYPE(NULL, PTR_TYPE_NULL);
 210
 211        /* consolidate this tree level, and parent levels, if possible */
 212        if (!n)
 213                return; /* cannot consolidate top level */
 214        /* first, build stack of ancestors between root and current node */
 215        parent_stack[0] = t->root;
 216        for (i = 0; i < n; i++) {
 217                j = GET_NIBBLE(i, entry->key_sha1);
 218                parent_stack[i + 1] = CLR_PTR_TYPE(parent_stack[i]->a[j]);
 219        }
 220        assert(i == n && parent_stack[i] == tree);
 221        /* next, unwind stack until note_tree_consolidate() is done */
 222        while (i > 0 &&
 223               !note_tree_consolidate(parent_stack[i], parent_stack[i - 1],
 224                                      GET_NIBBLE(i - 1, entry->key_sha1)))
 225                i--;
 226}
 227
 228/*
 229 * To insert a leaf_node:
 230 * Search to the tree location appropriate for the given leaf_node's key:
 231 * - If location is unused (NULL), store the tweaked pointer directly there
 232 * - If location holds a note entry that matches the note-to-be-inserted, then
 233 *   combine the two notes (by calling the given combine_notes function).
 234 * - If location holds a note entry that matches the subtree-to-be-inserted,
 235 *   then unpack the subtree-to-be-inserted into the location.
 236 * - If location holds a matching subtree entry, unpack the subtree at that
 237 *   location, and restart the insert operation from that level.
 238 * - Else, create a new int_node, holding both the node-at-location and the
 239 *   node-to-be-inserted, and store the new int_node into the location.
 240 */
 241static int note_tree_insert(struct notes_tree *t, struct int_node *tree,
 242                unsigned char n, struct leaf_node *entry, unsigned char type,
 243                combine_notes_fn combine_notes)
 244{
 245        struct int_node *new_node;
 246        struct leaf_node *l;
 247        void **p = note_tree_search(t, &tree, &n, entry->key_sha1);
 248        int ret = 0;
 249
 250        assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
 251        l = (struct leaf_node *) CLR_PTR_TYPE(*p);
 252        switch (GET_PTR_TYPE(*p)) {
 253        case PTR_TYPE_NULL:
 254                assert(!*p);
 255                if (is_null_sha1(entry->val_sha1))
 256                        free(entry);
 257                else
 258                        *p = SET_PTR_TYPE(entry, type);
 259                return 0;
 260        case PTR_TYPE_NOTE:
 261                switch (type) {
 262                case PTR_TYPE_NOTE:
 263                        if (!hashcmp(l->key_sha1, entry->key_sha1)) {
 264                                /* skip concatenation if l == entry */
 265                                if (!hashcmp(l->val_sha1, entry->val_sha1))
 266                                        return 0;
 267
 268                                ret = combine_notes(l->val_sha1,
 269                                                    entry->val_sha1);
 270                                if (!ret && is_null_sha1(l->val_sha1))
 271                                        note_tree_remove(t, tree, n, entry);
 272                                free(entry);
 273                                return ret;
 274                        }
 275                        break;
 276                case PTR_TYPE_SUBTREE:
 277                        if (!SUBTREE_SHA1_PREFIXCMP(l->key_sha1,
 278                                                    entry->key_sha1)) {
 279                                /* unpack 'entry' */
 280                                load_subtree(t, entry, tree, n);
 281                                free(entry);
 282                                return 0;
 283                        }
 284                        break;
 285                }
 286                break;
 287        case PTR_TYPE_SUBTREE:
 288                if (!SUBTREE_SHA1_PREFIXCMP(entry->key_sha1, l->key_sha1)) {
 289                        /* unpack 'l' and restart insert */
 290                        *p = NULL;
 291                        load_subtree(t, l, tree, n);
 292                        free(l);
 293                        return note_tree_insert(t, tree, n, entry, type,
 294                                                combine_notes);
 295                }
 296                break;
 297        }
 298
 299        /* non-matching leaf_node */
 300        assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
 301               GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
 302        if (is_null_sha1(entry->val_sha1)) { /* skip insertion of empty note */
 303                free(entry);
 304                return 0;
 305        }
 306        new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
 307        ret = note_tree_insert(t, new_node, n + 1, l, GET_PTR_TYPE(*p),
 308                               combine_notes);
 309        if (ret)
 310                return ret;
 311        *p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
 312        return note_tree_insert(t, new_node, n + 1, entry, type, combine_notes);
 313}
 314
 315/* Free the entire notes data contained in the given tree */
 316static void note_tree_free(struct int_node *tree)
 317{
 318        unsigned int i;
 319        for (i = 0; i < 16; i++) {
 320                void *p = tree->a[i];
 321                switch (GET_PTR_TYPE(p)) {
 322                case PTR_TYPE_INTERNAL:
 323                        note_tree_free(CLR_PTR_TYPE(p));
 324                        /* fall through */
 325                case PTR_TYPE_NOTE:
 326                case PTR_TYPE_SUBTREE:
 327                        free(CLR_PTR_TYPE(p));
 328                }
 329        }
 330}
 331
 332/*
 333 * Convert a partial SHA1 hex string to the corresponding partial SHA1 value.
 334 * - hex      - Partial SHA1 segment in ASCII hex format
 335 * - hex_len  - Length of above segment. Must be multiple of 2 between 0 and 40
 336 * - sha1     - Partial SHA1 value is written here
 337 * - sha1_len - Max #bytes to store in sha1, Must be >= hex_len / 2, and < 20
 338 * Returns -1 on error (invalid arguments or invalid SHA1 (not in hex format)).
 339 * Otherwise, returns number of bytes written to sha1 (i.e. hex_len / 2).
 340 * Pads sha1 with NULs up to sha1_len (not included in returned length).
 341 */
 342static int get_sha1_hex_segment(const char *hex, unsigned int hex_len,
 343                unsigned char *sha1, unsigned int sha1_len)
 344{
 345        unsigned int i, len = hex_len >> 1;
 346        if (hex_len % 2 != 0 || len > sha1_len)
 347                return -1;
 348        for (i = 0; i < len; i++) {
 349                unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
 350                if (val & ~0xff)
 351                        return -1;
 352                *sha1++ = val;
 353                hex += 2;
 354        }
 355        for (; i < sha1_len; i++)
 356                *sha1++ = 0;
 357        return len;
 358}
 359
 360static int non_note_cmp(const struct non_note *a, const struct non_note *b)
 361{
 362        return strcmp(a->path, b->path);
 363}
 364
 365static void add_non_note(struct notes_tree *t, const char *path,
 366                unsigned int mode, const unsigned char *sha1)
 367{
 368        struct non_note *p = t->prev_non_note, *n;
 369        n = (struct non_note *) xmalloc(sizeof(struct non_note));
 370        n->next = NULL;
 371        n->path = xstrdup(path);
 372        n->mode = mode;
 373        hashcpy(n->sha1, sha1);
 374        t->prev_non_note = n;
 375
 376        if (!t->first_non_note) {
 377                t->first_non_note = n;
 378                return;
 379        }
 380
 381        if (non_note_cmp(p, n) < 0)
 382                ; /* do nothing  */
 383        else if (non_note_cmp(t->first_non_note, n) <= 0)
 384                p = t->first_non_note;
 385        else {
 386                /* n sorts before t->first_non_note */
 387                n->next = t->first_non_note;
 388                t->first_non_note = n;
 389                return;
 390        }
 391
 392        /* n sorts equal or after p */
 393        while (p->next && non_note_cmp(p->next, n) <= 0)
 394                p = p->next;
 395
 396        if (non_note_cmp(p, n) == 0) { /* n ~= p; overwrite p with n */
 397                assert(strcmp(p->path, n->path) == 0);
 398                p->mode = n->mode;
 399                hashcpy(p->sha1, n->sha1);
 400                free(n);
 401                t->prev_non_note = p;
 402                return;
 403        }
 404
 405        /* n sorts between p and p->next */
 406        n->next = p->next;
 407        p->next = n;
 408}
 409
 410static void load_subtree(struct notes_tree *t, struct leaf_node *subtree,
 411                struct int_node *node, unsigned int n)
 412{
 413        unsigned char object_sha1[20];
 414        unsigned int prefix_len;
 415        void *buf;
 416        struct tree_desc desc;
 417        struct name_entry entry;
 418        int len, path_len;
 419        unsigned char type;
 420        struct leaf_node *l;
 421
 422        buf = fill_tree_descriptor(&desc, subtree->val_sha1);
 423        if (!buf)
 424                die("Could not read %s for notes-index",
 425                     sha1_to_hex(subtree->val_sha1));
 426
 427        prefix_len = subtree->key_sha1[19];
 428        assert(prefix_len * 2 >= n);
 429        memcpy(object_sha1, subtree->key_sha1, prefix_len);
 430        while (tree_entry(&desc, &entry)) {
 431                path_len = strlen(entry.path);
 432                len = get_sha1_hex_segment(entry.path, path_len,
 433                                object_sha1 + prefix_len, 20 - prefix_len);
 434                if (len < 0)
 435                        goto handle_non_note; /* entry.path is not a SHA1 */
 436                len += prefix_len;
 437
 438                /*
 439                 * If object SHA1 is complete (len == 20), assume note object
 440                 * If object SHA1 is incomplete (len < 20), and current
 441                 * component consists of 2 hex chars, assume note subtree
 442                 */
 443                if (len <= 20) {
 444                        type = PTR_TYPE_NOTE;
 445                        l = (struct leaf_node *)
 446                                xcalloc(sizeof(struct leaf_node), 1);
 447                        hashcpy(l->key_sha1, object_sha1);
 448                        hashcpy(l->val_sha1, entry.sha1);
 449                        if (len < 20) {
 450                                if (!S_ISDIR(entry.mode) || path_len != 2)
 451                                        goto handle_non_note; /* not subtree */
 452                                l->key_sha1[19] = (unsigned char) len;
 453                                type = PTR_TYPE_SUBTREE;
 454                        }
 455                        if (note_tree_insert(t, node, n, l, type,
 456                                             combine_notes_concatenate))
 457                                die("Failed to load %s %s into notes tree "
 458                                    "from %s",
 459                                    type == PTR_TYPE_NOTE ? "note" : "subtree",
 460                                    sha1_to_hex(l->key_sha1), t->ref);
 461                }
 462                continue;
 463
 464handle_non_note:
 465                /*
 466                 * Determine full path for this non-note entry:
 467                 * The filename is already found in entry.path, but the
 468                 * directory part of the path must be deduced from the subtree
 469                 * containing this entry. We assume here that the overall notes
 470                 * tree follows a strict byte-based progressive fanout
 471                 * structure (i.e. using 2/38, 2/2/36, etc. fanouts, and not
 472                 * e.g. 4/36 fanout). This means that if a non-note is found at
 473                 * path "dead/beef", the following code will register it as
 474                 * being found on "de/ad/beef".
 475                 * On the other hand, if you use such non-obvious non-note
 476                 * paths in the middle of a notes tree, you deserve what's
 477                 * coming to you ;). Note that for non-notes that are not
 478                 * SHA1-like at the top level, there will be no problems.
 479                 *
 480                 * To conclude, it is strongly advised to make sure non-notes
 481                 * have at least one non-hex character in the top-level path
 482                 * component.
 483                 */
 484                {
 485                        char non_note_path[PATH_MAX];
 486                        char *p = non_note_path;
 487                        const char *q = sha1_to_hex(subtree->key_sha1);
 488                        int i;
 489                        for (i = 0; i < prefix_len; i++) {
 490                                *p++ = *q++;
 491                                *p++ = *q++;
 492                                *p++ = '/';
 493                        }
 494                        strcpy(p, entry.path);
 495                        add_non_note(t, non_note_path, entry.mode, entry.sha1);
 496                }
 497        }
 498        free(buf);
 499}
 500
 501/*
 502 * Determine optimal on-disk fanout for this part of the notes tree
 503 *
 504 * Given a (sub)tree and the level in the internal tree structure, determine
 505 * whether or not the given existing fanout should be expanded for this
 506 * (sub)tree.
 507 *
 508 * Values of the 'fanout' variable:
 509 * - 0: No fanout (all notes are stored directly in the root notes tree)
 510 * - 1: 2/38 fanout
 511 * - 2: 2/2/36 fanout
 512 * - 3: 2/2/2/34 fanout
 513 * etc.
 514 */
 515static unsigned char determine_fanout(struct int_node *tree, unsigned char n,
 516                unsigned char fanout)
 517{
 518        /*
 519         * The following is a simple heuristic that works well in practice:
 520         * For each even-numbered 16-tree level (remember that each on-disk
 521         * fanout level corresponds to _two_ 16-tree levels), peek at all 16
 522         * entries at that tree level. If all of them are either int_nodes or
 523         * subtree entries, then there are likely plenty of notes below this
 524         * level, so we return an incremented fanout.
 525         */
 526        unsigned int i;
 527        if ((n % 2) || (n > 2 * fanout))
 528                return fanout;
 529        for (i = 0; i < 16; i++) {
 530                switch (GET_PTR_TYPE(tree->a[i])) {
 531                case PTR_TYPE_SUBTREE:
 532                case PTR_TYPE_INTERNAL:
 533                        continue;
 534                default:
 535                        return fanout;
 536                }
 537        }
 538        return fanout + 1;
 539}
 540
 541static void construct_path_with_fanout(const unsigned char *sha1,
 542                unsigned char fanout, char *path)
 543{
 544        unsigned int i = 0, j = 0;
 545        const char *hex_sha1 = sha1_to_hex(sha1);
 546        assert(fanout < 20);
 547        while (fanout) {
 548                path[i++] = hex_sha1[j++];
 549                path[i++] = hex_sha1[j++];
 550                path[i++] = '/';
 551                fanout--;
 552        }
 553        strcpy(path + i, hex_sha1 + j);
 554}
 555
 556static int for_each_note_helper(struct notes_tree *t, struct int_node *tree,
 557                unsigned char n, unsigned char fanout, int flags,
 558                each_note_fn fn, void *cb_data)
 559{
 560        unsigned int i;
 561        void *p;
 562        int ret = 0;
 563        struct leaf_node *l;
 564        static char path[40 + 19 + 1];  /* hex SHA1 + 19 * '/' + NUL */
 565
 566        fanout = determine_fanout(tree, n, fanout);
 567        for (i = 0; i < 16; i++) {
 568redo:
 569                p = tree->a[i];
 570                switch (GET_PTR_TYPE(p)) {
 571                case PTR_TYPE_INTERNAL:
 572                        /* recurse into int_node */
 573                        ret = for_each_note_helper(t, CLR_PTR_TYPE(p), n + 1,
 574                                fanout, flags, fn, cb_data);
 575                        break;
 576                case PTR_TYPE_SUBTREE:
 577                        l = (struct leaf_node *) CLR_PTR_TYPE(p);
 578                        /*
 579                         * Subtree entries in the note tree represent parts of
 580                         * the note tree that have not yet been explored. There
 581                         * is a direct relationship between subtree entries at
 582                         * level 'n' in the tree, and the 'fanout' variable:
 583                         * Subtree entries at level 'n <= 2 * fanout' should be
 584                         * preserved, since they correspond exactly to a fanout
 585                         * directory in the on-disk structure. However, subtree
 586                         * entries at level 'n > 2 * fanout' should NOT be
 587                         * preserved, but rather consolidated into the above
 588                         * notes tree level. We achieve this by unconditionally
 589                         * unpacking subtree entries that exist below the
 590                         * threshold level at 'n = 2 * fanout'.
 591                         */
 592                        if (n <= 2 * fanout &&
 593                            flags & FOR_EACH_NOTE_YIELD_SUBTREES) {
 594                                /* invoke callback with subtree */
 595                                unsigned int path_len =
 596                                        l->key_sha1[19] * 2 + fanout;
 597                                assert(path_len < 40 + 19);
 598                                construct_path_with_fanout(l->key_sha1, fanout,
 599                                                           path);
 600                                /* Create trailing slash, if needed */
 601                                if (path[path_len - 1] != '/')
 602                                        path[path_len++] = '/';
 603                                path[path_len] = '\0';
 604                                ret = fn(l->key_sha1, l->val_sha1, path,
 605                                         cb_data);
 606                        }
 607                        if (n > fanout * 2 ||
 608                            !(flags & FOR_EACH_NOTE_DONT_UNPACK_SUBTREES)) {
 609                                /* unpack subtree and resume traversal */
 610                                tree->a[i] = NULL;
 611                                load_subtree(t, l, tree, n);
 612                                free(l);
 613                                goto redo;
 614                        }
 615                        break;
 616                case PTR_TYPE_NOTE:
 617                        l = (struct leaf_node *) CLR_PTR_TYPE(p);
 618                        construct_path_with_fanout(l->key_sha1, fanout, path);
 619                        ret = fn(l->key_sha1, l->val_sha1, path, cb_data);
 620                        break;
 621                }
 622                if (ret)
 623                        return ret;
 624        }
 625        return 0;
 626}
 627
 628struct tree_write_stack {
 629        struct tree_write_stack *next;
 630        struct strbuf buf;
 631        char path[2]; /* path to subtree in next, if any */
 632};
 633
 634static inline int matches_tree_write_stack(struct tree_write_stack *tws,
 635                const char *full_path)
 636{
 637        return  full_path[0] == tws->path[0] &&
 638                full_path[1] == tws->path[1] &&
 639                full_path[2] == '/';
 640}
 641
 642static void write_tree_entry(struct strbuf *buf, unsigned int mode,
 643                const char *path, unsigned int path_len, const
 644                unsigned char *sha1)
 645{
 646        strbuf_addf(buf, "%o %.*s%c", mode, path_len, path, '\0');
 647        strbuf_add(buf, sha1, 20);
 648}
 649
 650static void tree_write_stack_init_subtree(struct tree_write_stack *tws,
 651                const char *path)
 652{
 653        struct tree_write_stack *n;
 654        assert(!tws->next);
 655        assert(tws->path[0] == '\0' && tws->path[1] == '\0');
 656        n = (struct tree_write_stack *)
 657                xmalloc(sizeof(struct tree_write_stack));
 658        n->next = NULL;
 659        strbuf_init(&n->buf, 256 * (32 + 40)); /* assume 256 entries per tree */
 660        n->path[0] = n->path[1] = '\0';
 661        tws->next = n;
 662        tws->path[0] = path[0];
 663        tws->path[1] = path[1];
 664}
 665
 666static int tree_write_stack_finish_subtree(struct tree_write_stack *tws)
 667{
 668        int ret;
 669        struct tree_write_stack *n = tws->next;
 670        unsigned char s[20];
 671        if (n) {
 672                ret = tree_write_stack_finish_subtree(n);
 673                if (ret)
 674                        return ret;
 675                ret = write_sha1_file(n->buf.buf, n->buf.len, tree_type, s);
 676                if (ret)
 677                        return ret;
 678                strbuf_release(&n->buf);
 679                free(n);
 680                tws->next = NULL;
 681                write_tree_entry(&tws->buf, 040000, tws->path, 2, s);
 682                tws->path[0] = tws->path[1] = '\0';
 683        }
 684        return 0;
 685}
 686
 687static int write_each_note_helper(struct tree_write_stack *tws,
 688                const char *path, unsigned int mode,
 689                const unsigned char *sha1)
 690{
 691        size_t path_len = strlen(path);
 692        unsigned int n = 0;
 693        int ret;
 694
 695        /* Determine common part of tree write stack */
 696        while (tws && 3 * n < path_len &&
 697               matches_tree_write_stack(tws, path + 3 * n)) {
 698                n++;
 699                tws = tws->next;
 700        }
 701
 702        /* tws point to last matching tree_write_stack entry */
 703        ret = tree_write_stack_finish_subtree(tws);
 704        if (ret)
 705                return ret;
 706
 707        /* Start subtrees needed to satisfy path */
 708        while (3 * n + 2 < path_len && path[3 * n + 2] == '/') {
 709                tree_write_stack_init_subtree(tws, path + 3 * n);
 710                n++;
 711                tws = tws->next;
 712        }
 713
 714        /* There should be no more directory components in the given path */
 715        assert(memchr(path + 3 * n, '/', path_len - (3 * n)) == NULL);
 716
 717        /* Finally add given entry to the current tree object */
 718        write_tree_entry(&tws->buf, mode, path + 3 * n, path_len - (3 * n),
 719                         sha1);
 720
 721        return 0;
 722}
 723
 724struct write_each_note_data {
 725        struct tree_write_stack *root;
 726        struct non_note *next_non_note;
 727};
 728
 729static int write_each_non_note_until(const char *note_path,
 730                struct write_each_note_data *d)
 731{
 732        struct non_note *n = d->next_non_note;
 733        int cmp = 0, ret;
 734        while (n && (!note_path || (cmp = strcmp(n->path, note_path)) <= 0)) {
 735                if (note_path && cmp == 0)
 736                        ; /* do nothing, prefer note to non-note */
 737                else {
 738                        ret = write_each_note_helper(d->root, n->path, n->mode,
 739                                                     n->sha1);
 740                        if (ret)
 741                                return ret;
 742                }
 743                n = n->next;
 744        }
 745        d->next_non_note = n;
 746        return 0;
 747}
 748
 749static int write_each_note(const unsigned char *object_sha1,
 750                const unsigned char *note_sha1, char *note_path,
 751                void *cb_data)
 752{
 753        struct write_each_note_data *d =
 754                (struct write_each_note_data *) cb_data;
 755        size_t note_path_len = strlen(note_path);
 756        unsigned int mode = 0100644;
 757
 758        if (note_path[note_path_len - 1] == '/') {
 759                /* subtree entry */
 760                note_path_len--;
 761                note_path[note_path_len] = '\0';
 762                mode = 040000;
 763        }
 764        assert(note_path_len <= 40 + 19);
 765
 766        /* Weave non-note entries into note entries */
 767        return  write_each_non_note_until(note_path, d) ||
 768                write_each_note_helper(d->root, note_path, mode, note_sha1);
 769}
 770
 771struct note_delete_list {
 772        struct note_delete_list *next;
 773        const unsigned char *sha1;
 774};
 775
 776static int prune_notes_helper(const unsigned char *object_sha1,
 777                const unsigned char *note_sha1, char *note_path,
 778                void *cb_data)
 779{
 780        struct note_delete_list **l = (struct note_delete_list **) cb_data;
 781        struct note_delete_list *n;
 782
 783        if (has_sha1_file(object_sha1))
 784                return 0; /* nothing to do for this note */
 785
 786        /* failed to find object => prune this note */
 787        n = (struct note_delete_list *) xmalloc(sizeof(*n));
 788        n->next = *l;
 789        n->sha1 = object_sha1;
 790        *l = n;
 791        return 0;
 792}
 793
 794int combine_notes_concatenate(unsigned char *cur_sha1,
 795                const unsigned char *new_sha1)
 796{
 797        char *cur_msg = NULL, *new_msg = NULL, *buf;
 798        unsigned long cur_len, new_len, buf_len;
 799        enum object_type cur_type, new_type;
 800        int ret;
 801
 802        /* read in both note blob objects */
 803        if (!is_null_sha1(new_sha1))
 804                new_msg = read_sha1_file(new_sha1, &new_type, &new_len);
 805        if (!new_msg || !new_len || new_type != OBJ_BLOB) {
 806                free(new_msg);
 807                return 0;
 808        }
 809        if (!is_null_sha1(cur_sha1))
 810                cur_msg = read_sha1_file(cur_sha1, &cur_type, &cur_len);
 811        if (!cur_msg || !cur_len || cur_type != OBJ_BLOB) {
 812                free(cur_msg);
 813                free(new_msg);
 814                hashcpy(cur_sha1, new_sha1);
 815                return 0;
 816        }
 817
 818        /* we will separate the notes by two newlines anyway */
 819        if (cur_msg[cur_len - 1] == '\n')
 820                cur_len--;
 821
 822        /* concatenate cur_msg and new_msg into buf */
 823        buf_len = cur_len + 2 + new_len;
 824        buf = (char *) xmalloc(buf_len);
 825        memcpy(buf, cur_msg, cur_len);
 826        buf[cur_len] = '\n';
 827        buf[cur_len + 1] = '\n';
 828        memcpy(buf + cur_len + 2, new_msg, new_len);
 829        free(cur_msg);
 830        free(new_msg);
 831
 832        /* create a new blob object from buf */
 833        ret = write_sha1_file(buf, buf_len, blob_type, cur_sha1);
 834        free(buf);
 835        return ret;
 836}
 837
 838int combine_notes_overwrite(unsigned char *cur_sha1,
 839                const unsigned char *new_sha1)
 840{
 841        hashcpy(cur_sha1, new_sha1);
 842        return 0;
 843}
 844
 845int combine_notes_ignore(unsigned char *cur_sha1,
 846                const unsigned char *new_sha1)
 847{
 848        return 0;
 849}
 850
 851/*
 852 * Add the lines from the named object to list, with trailing
 853 * newlines removed.
 854 */
 855static int string_list_add_note_lines(struct string_list *list,
 856                                      const unsigned char *sha1)
 857{
 858        char *data;
 859        unsigned long len;
 860        enum object_type t;
 861
 862        if (is_null_sha1(sha1))
 863                return 0;
 864
 865        /* read_sha1_file NUL-terminates */
 866        data = read_sha1_file(sha1, &t, &len);
 867        if (t != OBJ_BLOB || !data || !len) {
 868                free(data);
 869                return t != OBJ_BLOB || !data;
 870        }
 871
 872        /*
 873         * If the last line of the file is EOL-terminated, this will
 874         * add an empty string to the list.  But it will be removed
 875         * later, along with any empty strings that came from empty
 876         * lines within the file.
 877         */
 878        string_list_split(list, data, '\n', -1);
 879        free(data);
 880        return 0;
 881}
 882
 883static int string_list_join_lines_helper(struct string_list_item *item,
 884                                         void *cb_data)
 885{
 886        struct strbuf *buf = cb_data;
 887        strbuf_addstr(buf, item->string);
 888        strbuf_addch(buf, '\n');
 889        return 0;
 890}
 891
 892int combine_notes_cat_sort_uniq(unsigned char *cur_sha1,
 893                const unsigned char *new_sha1)
 894{
 895        struct string_list sort_uniq_list = STRING_LIST_INIT_DUP;
 896        struct strbuf buf = STRBUF_INIT;
 897        int ret = 1;
 898
 899        /* read both note blob objects into unique_lines */
 900        if (string_list_add_note_lines(&sort_uniq_list, cur_sha1))
 901                goto out;
 902        if (string_list_add_note_lines(&sort_uniq_list, new_sha1))
 903                goto out;
 904        string_list_remove_empty_items(&sort_uniq_list, 0);
 905        sort_string_list(&sort_uniq_list);
 906        string_list_remove_duplicates(&sort_uniq_list, 0);
 907
 908        /* create a new blob object from sort_uniq_list */
 909        if (for_each_string_list(&sort_uniq_list,
 910                                 string_list_join_lines_helper, &buf))
 911                goto out;
 912
 913        ret = write_sha1_file(buf.buf, buf.len, blob_type, cur_sha1);
 914
 915out:
 916        strbuf_release(&buf);
 917        string_list_clear(&sort_uniq_list, 0);
 918        return ret;
 919}
 920
 921static int string_list_add_one_ref(const char *path, const unsigned char *sha1,
 922                                   int flag, void *cb)
 923{
 924        struct string_list *refs = cb;
 925        if (!unsorted_string_list_has_string(refs, path))
 926                string_list_append(refs, path);
 927        return 0;
 928}
 929
 930void string_list_add_refs_by_glob(struct string_list *list, const char *glob)
 931{
 932        if (has_glob_specials(glob)) {
 933                for_each_glob_ref(string_list_add_one_ref, glob, list);
 934        } else {
 935                unsigned char sha1[20];
 936                if (get_sha1(glob, sha1))
 937                        warning("notes ref %s is invalid", glob);
 938                if (!unsorted_string_list_has_string(list, glob))
 939                        string_list_append(list, glob);
 940        }
 941}
 942
 943void string_list_add_refs_from_colon_sep(struct string_list *list,
 944                                         const char *globs)
 945{
 946        struct string_list split = STRING_LIST_INIT_NODUP;
 947        char *globs_copy = xstrdup(globs);
 948        int i;
 949
 950        string_list_split_in_place(&split, globs_copy, ':', -1);
 951        string_list_remove_empty_items(&split, 0);
 952
 953        for (i = 0; i < split.nr; i++)
 954                string_list_add_refs_by_glob(list, split.items[i].string);
 955
 956        string_list_clear(&split, 0);
 957        free(globs_copy);
 958}
 959
 960static int notes_display_config(const char *k, const char *v, void *cb)
 961{
 962        int *load_refs = cb;
 963
 964        if (*load_refs && !strcmp(k, "notes.displayref")) {
 965                if (!v)
 966                        config_error_nonbool(k);
 967                string_list_add_refs_by_glob(&display_notes_refs, v);
 968        }
 969
 970        return 0;
 971}
 972
 973const char *default_notes_ref(void)
 974{
 975        const char *notes_ref = NULL;
 976        if (!notes_ref)
 977                notes_ref = getenv(GIT_NOTES_REF_ENVIRONMENT);
 978        if (!notes_ref)
 979                notes_ref = notes_ref_name; /* value of core.notesRef config */
 980        if (!notes_ref)
 981                notes_ref = GIT_NOTES_DEFAULT_REF;
 982        return notes_ref;
 983}
 984
 985void init_notes(struct notes_tree *t, const char *notes_ref,
 986                combine_notes_fn combine_notes, int flags)
 987{
 988        unsigned char sha1[20], object_sha1[20];
 989        unsigned mode;
 990        struct leaf_node root_tree;
 991
 992        if (!t)
 993                t = &default_notes_tree;
 994        assert(!t->initialized);
 995
 996        if (!notes_ref)
 997                notes_ref = default_notes_ref();
 998
 999        if (!combine_notes)
1000                combine_notes = combine_notes_concatenate;
1001
1002        t->root = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
1003        t->first_non_note = NULL;
1004        t->prev_non_note = NULL;
1005        t->ref = notes_ref ? xstrdup(notes_ref) : NULL;
1006        t->combine_notes = combine_notes;
1007        t->initialized = 1;
1008        t->dirty = 0;
1009
1010        if (flags & NOTES_INIT_EMPTY || !notes_ref ||
1011            read_ref(notes_ref, object_sha1))
1012                return;
1013        if (get_tree_entry(object_sha1, "", sha1, &mode))
1014                die("Failed to read notes tree referenced by %s (%s)",
1015                    notes_ref, sha1_to_hex(object_sha1));
1016
1017        hashclr(root_tree.key_sha1);
1018        hashcpy(root_tree.val_sha1, sha1);
1019        load_subtree(t, &root_tree, t->root, 0);
1020}
1021
1022struct notes_tree **load_notes_trees(struct string_list *refs)
1023{
1024        struct string_list_item *item;
1025        int counter = 0;
1026        struct notes_tree **trees;
1027        trees = xmalloc((refs->nr+1) * sizeof(struct notes_tree *));
1028        for_each_string_list_item(item, refs) {
1029                struct notes_tree *t = xcalloc(1, sizeof(struct notes_tree));
1030                init_notes(t, item->string, combine_notes_ignore, 0);
1031                trees[counter++] = t;
1032        }
1033        trees[counter] = NULL;
1034        return trees;
1035}
1036
1037void init_display_notes(struct display_notes_opt *opt)
1038{
1039        char *display_ref_env;
1040        int load_config_refs = 0;
1041        display_notes_refs.strdup_strings = 1;
1042
1043        assert(!display_notes_trees);
1044
1045        if (!opt || opt->use_default_notes > 0 ||
1046            (opt->use_default_notes == -1 && !opt->extra_notes_refs.nr)) {
1047                string_list_append(&display_notes_refs, default_notes_ref());
1048                display_ref_env = getenv(GIT_NOTES_DISPLAY_REF_ENVIRONMENT);
1049                if (display_ref_env) {
1050                        string_list_add_refs_from_colon_sep(&display_notes_refs,
1051                                                            display_ref_env);
1052                        load_config_refs = 0;
1053                } else
1054                        load_config_refs = 1;
1055        }
1056
1057        git_config(notes_display_config, &load_config_refs);
1058
1059        if (opt) {
1060                struct string_list_item *item;
1061                for_each_string_list_item(item, &opt->extra_notes_refs)
1062                        string_list_add_refs_by_glob(&display_notes_refs,
1063                                                     item->string);
1064        }
1065
1066        display_notes_trees = load_notes_trees(&display_notes_refs);
1067        string_list_clear(&display_notes_refs, 0);
1068}
1069
1070int add_note(struct notes_tree *t, const unsigned char *object_sha1,
1071                const unsigned char *note_sha1, combine_notes_fn combine_notes)
1072{
1073        struct leaf_node *l;
1074
1075        if (!t)
1076                t = &default_notes_tree;
1077        assert(t->initialized);
1078        t->dirty = 1;
1079        if (!combine_notes)
1080                combine_notes = t->combine_notes;
1081        l = (struct leaf_node *) xmalloc(sizeof(struct leaf_node));
1082        hashcpy(l->key_sha1, object_sha1);
1083        hashcpy(l->val_sha1, note_sha1);
1084        return note_tree_insert(t, t->root, 0, l, PTR_TYPE_NOTE, combine_notes);
1085}
1086
1087int remove_note(struct notes_tree *t, const unsigned char *object_sha1)
1088{
1089        struct leaf_node l;
1090
1091        if (!t)
1092                t = &default_notes_tree;
1093        assert(t->initialized);
1094        hashcpy(l.key_sha1, object_sha1);
1095        hashclr(l.val_sha1);
1096        note_tree_remove(t, t->root, 0, &l);
1097        if (is_null_sha1(l.val_sha1)) /* no note was removed */
1098                return 1;
1099        t->dirty = 1;
1100        return 0;
1101}
1102
1103const unsigned char *get_note(struct notes_tree *t,
1104                const unsigned char *object_sha1)
1105{
1106        struct leaf_node *found;
1107
1108        if (!t)
1109                t = &default_notes_tree;
1110        assert(t->initialized);
1111        found = note_tree_find(t, t->root, 0, object_sha1);
1112        return found ? found->val_sha1 : NULL;
1113}
1114
1115int for_each_note(struct notes_tree *t, int flags, each_note_fn fn,
1116                void *cb_data)
1117{
1118        if (!t)
1119                t = &default_notes_tree;
1120        assert(t->initialized);
1121        return for_each_note_helper(t, t->root, 0, 0, flags, fn, cb_data);
1122}
1123
1124int write_notes_tree(struct notes_tree *t, unsigned char *result)
1125{
1126        struct tree_write_stack root;
1127        struct write_each_note_data cb_data;
1128        int ret;
1129
1130        if (!t)
1131                t = &default_notes_tree;
1132        assert(t->initialized);
1133
1134        /* Prepare for traversal of current notes tree */
1135        root.next = NULL; /* last forward entry in list is grounded */
1136        strbuf_init(&root.buf, 256 * (32 + 40)); /* assume 256 entries */
1137        root.path[0] = root.path[1] = '\0';
1138        cb_data.root = &root;
1139        cb_data.next_non_note = t->first_non_note;
1140
1141        /* Write tree objects representing current notes tree */
1142        ret = for_each_note(t, FOR_EACH_NOTE_DONT_UNPACK_SUBTREES |
1143                                FOR_EACH_NOTE_YIELD_SUBTREES,
1144                        write_each_note, &cb_data) ||
1145                write_each_non_note_until(NULL, &cb_data) ||
1146                tree_write_stack_finish_subtree(&root) ||
1147                write_sha1_file(root.buf.buf, root.buf.len, tree_type, result);
1148        strbuf_release(&root.buf);
1149        return ret;
1150}
1151
1152void prune_notes(struct notes_tree *t, int flags)
1153{
1154        struct note_delete_list *l = NULL;
1155
1156        if (!t)
1157                t = &default_notes_tree;
1158        assert(t->initialized);
1159
1160        for_each_note(t, 0, prune_notes_helper, &l);
1161
1162        while (l) {
1163                if (flags & NOTES_PRUNE_VERBOSE)
1164                        printf("%s\n", sha1_to_hex(l->sha1));
1165                if (!(flags & NOTES_PRUNE_DRYRUN))
1166                        remove_note(t, l->sha1);
1167                l = l->next;
1168        }
1169}
1170
1171void free_notes(struct notes_tree *t)
1172{
1173        if (!t)
1174                t = &default_notes_tree;
1175        if (t->root)
1176                note_tree_free(t->root);
1177        free(t->root);
1178        while (t->first_non_note) {
1179                t->prev_non_note = t->first_non_note->next;
1180                free(t->first_non_note->path);
1181                free(t->first_non_note);
1182                t->first_non_note = t->prev_non_note;
1183        }
1184        free(t->ref);
1185        memset(t, 0, sizeof(struct notes_tree));
1186}
1187
1188/*
1189 * Fill the given strbuf with the notes associated with the given object.
1190 *
1191 * If the given notes_tree structure is not initialized, it will be auto-
1192 * initialized to the default value (see documentation for init_notes() above).
1193 * If the given notes_tree is NULL, the internal/default notes_tree will be
1194 * used instead.
1195 *
1196 * (raw != 0) gives the %N userformat; otherwise, the note message is given
1197 * for human consumption.
1198 */
1199static void format_note(struct notes_tree *t, const unsigned char *object_sha1,
1200                        struct strbuf *sb, const char *output_encoding, int raw)
1201{
1202        static const char utf8[] = "utf-8";
1203        const unsigned char *sha1;
1204        char *msg, *msg_p;
1205        unsigned long linelen, msglen;
1206        enum object_type type;
1207
1208        if (!t)
1209                t = &default_notes_tree;
1210        if (!t->initialized)
1211                init_notes(t, NULL, NULL, 0);
1212
1213        sha1 = get_note(t, object_sha1);
1214        if (!sha1)
1215                return;
1216
1217        if (!(msg = read_sha1_file(sha1, &type, &msglen)) || !msglen ||
1218                        type != OBJ_BLOB) {
1219                free(msg);
1220                return;
1221        }
1222
1223        if (output_encoding && *output_encoding &&
1224            !is_encoding_utf8(output_encoding)) {
1225                char *reencoded = reencode_string(msg, output_encoding, utf8);
1226                if (reencoded) {
1227                        free(msg);
1228                        msg = reencoded;
1229                        msglen = strlen(msg);
1230                }
1231        }
1232
1233        /* we will end the annotation by a newline anyway */
1234        if (msglen && msg[msglen - 1] == '\n')
1235                msglen--;
1236
1237        if (!raw) {
1238                const char *ref = t->ref;
1239                if (!ref || !strcmp(ref, GIT_NOTES_DEFAULT_REF)) {
1240                        strbuf_addstr(sb, "\nNotes:\n");
1241                } else {
1242                        if (!prefixcmp(ref, "refs/"))
1243                                ref += 5;
1244                        if (!prefixcmp(ref, "notes/"))
1245                                ref += 6;
1246                        strbuf_addf(sb, "\nNotes (%s):\n", ref);
1247                }
1248        }
1249
1250        for (msg_p = msg; msg_p < msg + msglen; msg_p += linelen + 1) {
1251                linelen = strchrnul(msg_p, '\n') - msg_p;
1252
1253                if (!raw)
1254                        strbuf_addstr(sb, "    ");
1255                strbuf_add(sb, msg_p, linelen);
1256                strbuf_addch(sb, '\n');
1257        }
1258
1259        free(msg);
1260}
1261
1262void format_display_notes(const unsigned char *object_sha1,
1263                          struct strbuf *sb, const char *output_encoding, int raw)
1264{
1265        int i;
1266        assert(display_notes_trees);
1267        for (i = 0; display_notes_trees[i]; i++)
1268                format_note(display_notes_trees[i], object_sha1, sb,
1269                            output_encoding, raw);
1270}
1271
1272int copy_note(struct notes_tree *t,
1273              const unsigned char *from_obj, const unsigned char *to_obj,
1274              int force, combine_notes_fn combine_notes)
1275{
1276        const unsigned char *note = get_note(t, from_obj);
1277        const unsigned char *existing_note = get_note(t, to_obj);
1278
1279        if (!force && existing_note)
1280                return 1;
1281
1282        if (note)
1283                return add_note(t, to_obj, note, combine_notes);
1284        else if (existing_note)
1285                return add_note(t, to_obj, null_sha1, combine_notes);
1286
1287        return 0;
1288}
1289
1290void expand_notes_ref(struct strbuf *sb)
1291{
1292        if (!prefixcmp(sb->buf, "refs/notes/"))
1293                return; /* we're happy */
1294        else if (!prefixcmp(sb->buf, "notes/"))
1295                strbuf_insert(sb, 0, "refs/", 5);
1296        else
1297                strbuf_insert(sb, 0, "refs/notes/", 11);
1298}