#include "cache.h"
#include "tag.h"
#include "commit.h"
#include "pkt-line.h"
#include "utf8.h"
#include "diff.h"
#include "revision.h"
#include "notes.h"
#include "gpg-interface.h"
#include "mergesort.h"

static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);

int save_commit_buffer = 1;

const char *commit_type = "commit";
static int commit_count;

static struct commit *check_commit(struct object *obj,
                                   const unsigned char *sha1,
                                   int quiet)
{
        if (obj->type != OBJ_COMMIT) {
                if (!quiet)
                        error("Object %s is a %s, not a commit",
                              sha1_to_hex(sha1), typename(obj->type));
                return NULL;
        }
        return (struct commit *) obj;
}

struct commit *lookup_commit_reference_gently(const unsigned char *sha1,
                                              int quiet)
{
        struct object *obj = deref_tag(parse_object(sha1), NULL, 0);

        if (!obj)
                return NULL;
        return check_commit(obj, sha1, quiet);
}

struct commit *lookup_commit_reference(const unsigned char *sha1)
{
        return lookup_commit_reference_gently(sha1, 0);
}

struct commit *lookup_commit_or_die(const unsigned char *sha1, const char *ref_name)
{
        struct commit *c = lookup_commit_reference(sha1);
        if (!c)
                die(_("could not parse %s"), ref_name);
        if (hashcmp(sha1, c->object.sha1)) {
                warning(_("%s %s is not a commit!"),
                        ref_name, sha1_to_hex(sha1));
        }
        return c;
}

struct commit *lookup_commit(const unsigned char *sha1)
{
        struct object *obj = lookup_object(sha1);
        if (!obj) {
                struct commit *c = alloc_commit_node();
                c->index = commit_count++;
                return create_object(sha1, OBJ_COMMIT, c);
        }
        if (!obj->type)
                obj->type = OBJ_COMMIT;
        return check_commit(obj, sha1, 0);
}

struct commit *lookup_commit_reference_by_name(const char *name)
{
        unsigned char sha1[20];
        struct commit *commit;

        if (get_sha1_committish(name, sha1))
                return NULL;
        commit = lookup_commit_reference(sha1);
        if (!commit || parse_commit(commit))
                return NULL;
        return commit;
}

static unsigned long parse_commit_date(const char *buf, const char *tail)
{
        const char *dateptr;

        if (buf + 6 >= tail)
                return 0;
        if (memcmp(buf, "author", 6))
                return 0;
        while (buf < tail && *buf++ != '\n')
                /* nada */;
        if (buf + 9 >= tail)
                return 0;
        if (memcmp(buf, "committer", 9))
                return 0;
        while (buf < tail && *buf++ != '>')
                /* nada */;
        if (buf >= tail)
                return 0;
        dateptr = buf;
        while (buf < tail && *buf++ != '\n')
                /* nada */;
        if (buf >= tail)
                return 0;
        /* dateptr < buf && buf[-1] == '\n', so strtoul will stop at buf-1 */
        return strtoul(dateptr, NULL, 10);
}

static struct commit_graft **commit_graft;
static int commit_graft_alloc, commit_graft_nr;

static int commit_graft_pos(const unsigned char *sha1)
{
        int lo, hi;
        lo = 0;
        hi = commit_graft_nr;
        while (lo < hi) {
                int mi = (lo + hi) / 2;
                struct commit_graft *graft = commit_graft[mi];
                int cmp = hashcmp(sha1, graft->sha1);
                if (!cmp)
                        return mi;
                if (cmp < 0)
                        hi = mi;
                else
                        lo = mi + 1;
        }
        return -lo - 1;
}

int register_commit_graft(struct commit_graft *graft, int ignore_dups)
{
        int pos = commit_graft_pos(graft->sha1);

        if (0 <= pos) {
                if (ignore_dups)
                        free(graft);
                else {
                        free(commit_graft[pos]);
                        commit_graft[pos] = graft;
                }
                return 1;
        }
        pos = -pos - 1;
        if (commit_graft_alloc <= ++commit_graft_nr) {
                commit_graft_alloc = alloc_nr(commit_graft_alloc);
                commit_graft = xrealloc(commit_graft,
                                        sizeof(*commit_graft) *
                                        commit_graft_alloc);
        }
        if (pos < commit_graft_nr)
                memmove(commit_graft + pos + 1,
                        commit_graft + pos,
                        (commit_graft_nr - pos - 1) *
                        sizeof(*commit_graft));
        commit_graft[pos] = graft;
        return 0;
}

struct commit_graft *read_graft_line(char *buf, int len)
{
        /* The format is just "Commit Parent1 Parent2 ...\n" */
        int i;
        struct commit_graft *graft = NULL;

        while (len && isspace(buf[len-1]))
                buf[--len] = '\0';
        if (buf[0] == '#' || buf[0] == '\0')
                return NULL;
        if ((len + 1) % 41)
                goto bad_graft_data;
        i = (len + 1) / 41 - 1;
        graft = xmalloc(sizeof(*graft) + 20 * i);
        graft->nr_parent = i;
        if (get_sha1_hex(buf, graft->sha1))
                goto bad_graft_data;
        for (i = 40; i < len; i += 41) {
                if (buf[i] != ' ')
                        goto bad_graft_data;
                if (get_sha1_hex(buf + i + 1, graft->parent[i/41]))
                        goto bad_graft_data;
        }
        return graft;

bad_graft_data:
        error("bad graft data: %s", buf);
        free(graft);
        return NULL;
}

static int read_graft_file(const char *graft_file)
{
        FILE *fp = fopen(graft_file, "r");
        char buf[1024];
        if (!fp)
                return -1;
        while (fgets(buf, sizeof(buf), fp)) {
                /* The format is just "Commit Parent1 Parent2 ...\n" */
                int len = strlen(buf);
                struct commit_graft *graft = read_graft_line(buf, len);
                if (!graft)
                        continue;
                if (register_commit_graft(graft, 1))
                        error("duplicate graft data: %s", buf);
        }
        fclose(fp);
        return 0;
}

static void prepare_commit_graft(void)
{
        static int commit_graft_prepared;
        char *graft_file;

        if (commit_graft_prepared)
                return;
        graft_file = get_graft_file();
        read_graft_file(graft_file);
        /* make sure shallows are read */
        is_repository_shallow();
        commit_graft_prepared = 1;
}

struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
{
        int pos;
        prepare_commit_graft();
        pos = commit_graft_pos(sha1);
        if (pos < 0)
                return NULL;
        return commit_graft[pos];
}

int for_each_commit_graft(each_commit_graft_fn fn, void *cb_data)
{
        int i, ret;
        for (i = ret = 0; i < commit_graft_nr && !ret; i++)
                ret = fn(commit_graft[i], cb_data);
        return ret;
}

int unregister_shallow(const unsigned char *sha1)
{
        int pos = commit_graft_pos(sha1);
        if (pos < 0)
                return -1;
        if (pos + 1 < commit_graft_nr)
                memmove(commit_graft + pos, commit_graft + pos + 1,
                                sizeof(struct commit_graft *)
                                * (commit_graft_nr - pos - 1));
        commit_graft_nr--;
        return 0;
}

int parse_commit_buffer(struct commit *item, const void *buffer, unsigned long size)
{
        const char *tail = buffer;
        const char *bufptr = buffer;
        unsigned char parent[20];
        struct commit_list **pptr;
        struct commit_graft *graft;

        if (item->object.parsed)
                return 0;
        item->object.parsed = 1;
        tail += size;
        if (tail <= bufptr + 46 || memcmp(bufptr, "tree ", 5) || bufptr[45] != '\n')
                return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
        if (get_sha1_hex(bufptr + 5, parent) < 0)
                return error("bad tree pointer in commit %s",
                             sha1_to_hex(item->object.sha1));
        item->tree = lookup_tree(parent);
        bufptr += 46; /* "tree " + "hex sha1" + "\n" */
        pptr = &item->parents;

        graft = lookup_commit_graft(item->object.sha1);
        while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
                struct commit *new_parent;

                if (tail <= bufptr + 48 ||
                    get_sha1_hex(bufptr + 7, parent) ||
                    bufptr[47] != '\n')
                        return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
                bufptr += 48;
                /*
                 * The clone is shallow if nr_parent < 0, and we must
                 * not traverse its real parents even when we unhide them.
                 */
                if (graft && (graft->nr_parent < 0 || grafts_replace_parents))
                        continue;
                new_parent = lookup_commit(parent);
                if (new_parent)
                        pptr = &commit_list_insert(new_parent, pptr)->next;
        }
        if (graft) {
                int i;
                struct commit *new_parent;
                for (i = 0; i < graft->nr_parent; i++) {
                        new_parent = lookup_commit(graft->parent[i]);
                        if (!new_parent)
                                continue;
                        pptr = &commit_list_insert(new_parent, pptr)->next;
                }
        }
        item->date = parse_commit_date(bufptr, tail);

        return 0;
}

int parse_commit(struct commit *item)
{
        enum object_type type;
        void *buffer;
        unsigned long size;
        int ret;

        if (!item)
                return -1;
        if (item->object.parsed)
                return 0;
        buffer = read_sha1_file(item->object.sha1, &type, &size);
        if (!buffer)
                return error("Could not read %s",
                             sha1_to_hex(item->object.sha1));
        if (type != OBJ_COMMIT) {
                free(buffer);
                return error("Object %s not a commit",
                             sha1_to_hex(item->object.sha1));
        }
        ret = parse_commit_buffer(item, buffer, size);
        if (save_commit_buffer && !ret) {
                item->buffer = buffer;
                return 0;
        }
        free(buffer);
        return ret;
}

int find_commit_subject(const char *commit_buffer, const char **subject)
{
        const char *eol;
        const char *p = commit_buffer;

        while (*p && (*p != '\n' || p[1] != '\n'))
                p++;
        if (*p) {
                p += 2;
                for (eol = p; *eol && *eol != '\n'; eol++)
                        ; /* do nothing */
        } else
                eol = p;

        *subject = p;

        return eol - p;
}

struct commit_list *commit_list_insert(struct commit *item, struct commit_list **list_p)
{
        struct commit_list *new_list = xmalloc(sizeof(struct commit_list));
        new_list->item = item;
        new_list->next = *list_p;
        *list_p = new_list;
        return new_list;
}

unsigned commit_list_count(const struct commit_list *l)
{
        unsigned c = 0;
        for (; l; l = l->next )
                c++;
        return c;
}

void free_commit_list(struct commit_list *list)
{
        while (list) {
                struct commit_list *temp = list;
                list = temp->next;
                free(temp);
        }
}

struct commit_list * commit_list_insert_by_date(struct commit *item, struct commit_list **list)
{
        struct commit_list **pp = list;
        struct commit_list *p;
        while ((p = *pp) != NULL) {
                if (p->item->date < item->date) {
                        break;
                }
                pp = &p->next;
        }
        return commit_list_insert(item, pp);
}

static int commit_list_compare_by_date(const void *a, const void *b)
{
        unsigned long a_date = ((const struct commit_list *)a)->item->date;
        unsigned long b_date = ((const struct commit_list *)b)->item->date;
        if (a_date < b_date)
                return 1;
        if (a_date > b_date)
                return -1;
        return 0;
}

static void *commit_list_get_next(const void *a)
{
        return ((const struct commit_list *)a)->next;
}

static void commit_list_set_next(void *a, void *next)
{
        ((struct commit_list *)a)->next = next;
}

void commit_list_sort_by_date(struct commit_list **list)
{
        *list = llist_mergesort(*list, commit_list_get_next, commit_list_set_next,
                                commit_list_compare_by_date);
}

struct commit *pop_most_recent_commit(struct commit_list **list,
                                      unsigned int mark)
{
        struct commit *ret = (*list)->item;
        struct commit_list *parents = ret->parents;
        struct commit_list *old = *list;

        *list = (*list)->next;
        free(old);

        while (parents) {
                struct commit *commit = parents->item;
                if (!parse_commit(commit) && !(commit->object.flags & mark)) {
                        commit->object.flags |= mark;
                        commit_list_insert_by_date(commit, list);
                }
                parents = parents->next;
        }
        return ret;
}

static void clear_commit_marks_1(struct commit_list **plist,
                                 struct commit *commit, unsigned int mark)
{
        while (commit) {
                struct commit_list *parents;

                if (!(mark & commit->object.flags))
                        return;

                commit->object.flags &= ~mark;

                parents = commit->parents;
                if (!parents)
                        return;

                while ((parents = parents->next))
                        commit_list_insert(parents->item, plist);

                commit = commit->parents->item;
        }
}

void clear_commit_marks(struct commit *commit, unsigned int mark)
{
        struct commit_list *list = NULL;
        commit_list_insert(commit, &list);
        while (list)
                clear_commit_marks_1(&list, pop_commit(&list), mark);
}

void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark)
{
        struct object *object;
        struct commit *commit;
        unsigned int i;

        for (i = 0; i < a->nr; i++) {
                object = a->objects[i].item;
                commit = lookup_commit_reference_gently(object->sha1, 1);
                if (commit)
                        clear_commit_marks(commit, mark);
        }
}

struct commit *pop_commit(struct commit_list **stack)
{
        struct commit_list *top = *stack;
        struct commit *item = top ? top->item : NULL;

        if (top) {
                *stack = top->next;
                free(top);
        }
        return item;
}

struct commit_slab_piece {
        int buf;
};

struct commit_slab {
        int piece_size;
        int piece_count;
        struct commit_slab_piece **piece;
};

static void slab_init(struct commit_slab *s)
{
        /* allocate ~512kB at once, allowing for malloc overhead */
        int size = (512*1024-32) / sizeof(struct commit_slab_piece);

        s->piece_size = size;
        s->piece_count = 0;
        s->piece = NULL;
}

static void slab_clear(struct commit_slab *s)
{
        int i;

        for (i = 0; i < s->piece_count; i++)
                free(s->piece[i]);
        s->piece_count = 0;
        free(s->piece);
        s->piece = NULL;
}

static inline struct commit_slab_piece *slab_at(struct commit_slab *s,
                                                const struct commit *c)
{
        int nth_piece, nth_slot;

        nth_piece = c->index / s->piece_size;
        nth_slot = c->index % s->piece_size;

        if (s->piece_count <= nth_piece) {
                int i;

                s->piece = xrealloc(s->piece, (nth_piece + 1) * sizeof(s->piece));
                for (i = s->piece_count; i <= nth_piece; i++)
                        s->piece[i] = NULL;
                s->piece_count = nth_piece + 1;
        }
        if (!s->piece[nth_piece])
                s->piece[nth_piece] = xcalloc(s->piece_size, sizeof(**s->piece));
        return &s->piece[nth_piece][nth_slot];
}

/*
 * Performs an in-place topological sort on the list supplied.
 */
void sort_in_topological_order(struct commit_list ** list, int lifo)
{
        struct commit_list *next, *orig = *list;
        struct commit_list *work, **insert;
        struct commit_list **pptr;
        struct commit_slab indegree;

        if (!orig)
                return;
        *list = NULL;

        slab_init(&indegree);

        /* Mark them and clear the indegree */
        for (next = orig; next; next = next->next) {
                struct commit *commit = next->item;
                slab_at(&indegree, commit)->buf = 1;
        }

        /* update the indegree */
        for (next = orig; next; next = next->next) {
                struct commit_list * parents = next->item->parents;
                while (parents) {
                        struct commit *parent = parents->item;
                        int *pi = &slab_at(&indegree, parent)->buf;

                        if (*pi)
                                (*pi)++;
                        parents = parents->next;
                }
        }

        /*
         * find the tips
         *
         * tips are nodes not reachable from any other node in the list
         *
         * the tips serve as a starting set for the work queue.
         */
        work = NULL;
        insert = &work;
        for (next = orig; next; next = next->next) {
                struct commit *commit = next->item;

                if (slab_at(&indegree, commit)->buf == 1)
                        insert = &commit_list_insert(commit, insert)->next;
        }

        /* process the list in topological order */
        if (!lifo)
                commit_list_sort_by_date(&work);

        pptr = list;
        *list = NULL;
        while (work) {
                struct commit *commit;
                struct commit_list *parents, *work_item;

                work_item = work;
                work = work_item->next;
                work_item->next = NULL;

                commit = work_item->item;
                for (parents = commit->parents; parents ; parents = parents->next) {
                        struct commit *parent = parents->item;
                        int *pi = &slab_at(&indegree, parent)->buf;

                        if (!*pi)
                                continue;

                        /*
                         * parents are only enqueued for emission
                         * when all their children have been emitted thereby
                         * guaranteeing topological order.
                         */
                        if (--(*pi) == 1) {
                                if (!lifo)
                                        commit_list_insert_by_date(parent, &work);
                                else
                                        commit_list_insert(parent, &work);
                        }
                }
                /*
                 * work_item is a commit all of whose children
                 * have already been emitted. we can emit it now.
                 */
                slab_at(&indegree, commit)->buf = 0;
                *pptr = work_item;
                pptr = &work_item->next;
        }

        slab_clear(&indegree);
}

/* merge-base stuff */

/* bits #0..15 in revision.h */
#define PARENT1         (1u<<16)
#define PARENT2         (1u<<17)
#define STALE           (1u<<18)
#define RESULT          (1u<<19)

static const unsigned all_flags = (PARENT1 | PARENT2 | STALE | RESULT);

static struct commit *interesting(struct commit_list *list)
{
        while (list) {
                struct commit *commit = list->item;
                list = list->next;
                if (commit->object.flags & STALE)
                        continue;
                return commit;
        }
        return NULL;
}

/* all input commits in one and twos[] must have been parsed! */
static struct commit_list *paint_down_to_common(struct commit *one, int n, struct commit **twos)
{
        struct commit_list *list = NULL;
        struct commit_list *result = NULL;
        int i;

        one->object.flags |= PARENT1;
        commit_list_insert_by_date(one, &list);
        if (!n)
                return list;
        for (i = 0; i < n; i++) {
                twos[i]->object.flags |= PARENT2;
                commit_list_insert_by_date(twos[i], &list);
        }

        while (interesting(list)) {
                struct commit *commit;
                struct commit_list *parents;
                struct commit_list *next;
                int flags;

                commit = list->item;
                next = list->next;
                free(list);
                list = next;

                flags = commit->object.flags & (PARENT1 | PARENT2 | STALE);
                if (flags == (PARENT1 | PARENT2)) {
                        if (!(commit->object.flags & RESULT)) {
                                commit->object.flags |= RESULT;
                                commit_list_insert_by_date(commit, &result);
                        }
                        /* Mark parents of a found merge stale */
                        flags |= STALE;
                }
                parents = commit->parents;
                while (parents) {
                        struct commit *p = parents->item;
                        parents = parents->next;
                        if ((p->object.flags & flags) == flags)
                                continue;
                        if (parse_commit(p))
                                return NULL;
                        p->object.flags |= flags;
                        commit_list_insert_by_date(p, &list);
                }
        }

        free_commit_list(list);
        return result;
}

static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
{
        struct commit_list *list = NULL;
        struct commit_list *result = NULL;
        int i;

        for (i = 0; i < n; i++) {
                if (one == twos[i])
                        /*
                         * We do not mark this even with RESULT so we do not
                         * have to clean it up.
                         */
                        return commit_list_insert(one, &result);
        }

        if (parse_commit(one))
                return NULL;
        for (i = 0; i < n; i++) {
                if (parse_commit(twos[i]))
                        return NULL;
        }

        list = paint_down_to_common(one, n, twos);

        while (list) {
                struct commit_list *next = list->next;
                if (!(list->item->object.flags & STALE))
                        commit_list_insert_by_date(list->item, &result);
                free(list);
                list = next;
        }
        return result;
}

struct commit_list *get_octopus_merge_bases(struct commit_list *in)
{
        struct commit_list *i, *j, *k, *ret = NULL;
        struct commit_list **pptr = &ret;

        for (i = in; i; i = i->next) {
                if (!ret)
                        pptr = &commit_list_insert(i->item, pptr)->next;
                else {
                        struct commit_list *new = NULL, *end = NULL;

                        for (j = ret; j; j = j->next) {
                                struct commit_list *bases;
                                bases = get_merge_bases(i->item, j->item, 1);
                                if (!new)
                                        new = bases;
                                else
                                        end->next = bases;
                                for (k = bases; k; k = k->next)
                                        end = k;
                        }
                        ret = new;
                }
        }
        return ret;
}

static int remove_redundant(struct commit **array, int cnt)
{
        /*
         * Some commit in the array may be an ancestor of
         * another commit.  Move such commit to the end of
         * the array, and return the number of commits that
         * are independent from each other.
         */
        struct commit **work;
        unsigned char *redundant;
        int *filled_index;
        int i, j, filled;

        work = xcalloc(cnt, sizeof(*work));
        redundant = xcalloc(cnt, 1);
        filled_index = xmalloc(sizeof(*filled_index) * (cnt - 1));

        for (i = 0; i < cnt; i++)
                parse_commit(array[i]);
        for (i = 0; i < cnt; i++) {
                struct commit_list *common;

                if (redundant[i])
                        continue;
                for (j = filled = 0; j < cnt; j++) {
                        if (i == j || redundant[j])
                                continue;
                        filled_index[filled] = j;
                        work[filled++] = array[j];
                }
                common = paint_down_to_common(array[i], filled, work);
                if (array[i]->object.flags & PARENT2)
                        redundant[i] = 1;
                for (j = 0; j < filled; j++)
                        if (work[j]->object.flags & PARENT1)
                                redundant[filled_index[j]] = 1;
                clear_commit_marks(array[i], all_flags);
                for (j = 0; j < filled; j++)
                        clear_commit_marks(work[j], all_flags);
                free_commit_list(common);
        }

        /* Now collect the result */
        memcpy(work, array, sizeof(*array) * cnt);
        for (i = filled = 0; i < cnt; i++)
                if (!redundant[i])
                        array[filled++] = work[i];
        for (j = filled, i = 0; i < cnt; i++)
                if (redundant[i])
                        array[j++] = work[i];
        free(work);
        free(redundant);
        free(filled_index);
        return filled;
}

struct commit_list *get_merge_bases_many(struct commit *one,
                                         int n,
                                         struct commit **twos,
                                         int cleanup)
{
        struct commit_list *list;
        struct commit **rslt;
        struct commit_list *result;
        int cnt, i;

        result = merge_bases_many(one, n, twos);
        for (i = 0; i < n; i++) {
                if (one == twos[i])
                        return result;
        }
        if (!result || !result->next) {
                if (cleanup) {
                        clear_commit_marks(one, all_flags);
                        for (i = 0; i < n; i++)
                                clear_commit_marks(twos[i], all_flags);
                }
                return result;
        }

        /* There are more than one */
        cnt = 0;
        list = result;
        while (list) {
                list = list->next;
                cnt++;
        }
        rslt = xcalloc(cnt, sizeof(*rslt));
        for (list = result, i = 0; list; list = list->next)
                rslt[i++] = list->item;
        free_commit_list(result);

        clear_commit_marks(one, all_flags);
        for (i = 0; i < n; i++)
                clear_commit_marks(twos[i], all_flags);

        cnt = remove_redundant(rslt, cnt);
        result = NULL;
        for (i = 0; i < cnt; i++)
                commit_list_insert_by_date(rslt[i], &result);
        free(rslt);
        return result;
}

struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
                                    int cleanup)
{
        return get_merge_bases_many(one, 1, &two, cleanup);
}

/*
 * Is "commit" a descendant of one of the elements on the "with_commit" list?
 */
int is_descendant_of(struct commit *commit, struct commit_list *with_commit)
{
        if (!with_commit)
                return 1;
        while (with_commit) {
                struct commit *other;

                other = with_commit->item;
                with_commit = with_commit->next;
                if (in_merge_bases(other, commit))
                        return 1;
        }
        return 0;
}

/*
 * Is "commit" an ancestor of (i.e. reachable from) the "reference"?
 */
int in_merge_bases(struct commit *commit, struct commit *reference)
{
        struct commit_list *bases;
        int ret = 0;

        if (parse_commit(commit) || parse_commit(reference))
                return ret;

        bases = paint_down_to_common(commit, 1, &reference);
        if (commit->object.flags & PARENT2)
                ret = 1;
        clear_commit_marks(commit, all_flags);
        clear_commit_marks(reference, all_flags);
        free_commit_list(bases);
        return ret;
}

struct commit_list *reduce_heads(struct commit_list *heads)
{
        struct commit_list *p;
        struct commit_list *result = NULL, **tail = &result;
        struct commit **array;
        int num_head, i;

        if (!heads)
                return NULL;

        /* Uniquify */
        for (p = heads; p; p = p->next)
                p->item->object.flags &= ~STALE;
        for (p = heads, num_head = 0; p; p = p->next) {
                if (p->item->object.flags & STALE)
                        continue;
                p->item->object.flags |= STALE;
                num_head++;
        }
        array = xcalloc(sizeof(*array), num_head);
        for (p = heads, i = 0; p; p = p->next) {
                if (p->item->object.flags & STALE) {
                        array[i++] = p->item;
                        p->item->object.flags &= ~STALE;
                }
        }
        num_head = remove_redundant(array, num_head);
        for (i = 0; i < num_head; i++)
                tail = &commit_list_insert(array[i], tail)->next;
        return result;
}

static const char gpg_sig_header[] = "gpgsig";
static const int gpg_sig_header_len = sizeof(gpg_sig_header) - 1;

static int do_sign_commit(struct strbuf *buf, const char *keyid)
{
        struct strbuf sig = STRBUF_INIT;
        int inspos, copypos;

        /* find the end of the header */
        inspos = strstr(buf->buf, "\n\n") - buf->buf + 1;

        if (!keyid || !*keyid)
                keyid = get_signing_key();
        if (sign_buffer(buf, &sig, keyid)) {
                strbuf_release(&sig);
                return -1;
        }

        for (copypos = 0; sig.buf[copypos]; ) {
                const char *bol = sig.buf + copypos;
                const char *eol = strchrnul(bol, '\n');
                int len = (eol - bol) + !!*eol;

                if (!copypos) {
                        strbuf_insert(buf, inspos, gpg_sig_header, gpg_sig_header_len);
                        inspos += gpg_sig_header_len;
                }
                strbuf_insert(buf, inspos++, " ", 1);
                strbuf_insert(buf, inspos, bol, len);
                inspos += len;
                copypos += len;
        }
        strbuf_release(&sig);
        return 0;
}

int parse_signed_commit(const unsigned char *sha1,
                        struct strbuf *payload, struct strbuf *signature)
{
        unsigned long size;
        enum object_type type;
        char *buffer = read_sha1_file(sha1, &type, &size);
        int in_signature, saw_signature = -1;
        char *line, *tail;

        if (!buffer || type != OBJ_COMMIT)
                goto cleanup;

        line = buffer;
        tail = buffer + size;
        in_signature = 0;
        saw_signature = 0;
        while (line < tail) {
                const char *sig = NULL;
                char *next = memchr(line, '\n', tail - line);

                next = next ? next + 1 : tail;
                if (in_signature && line[0] == ' ')
                        sig = line + 1;
                else if (!prefixcmp(line, gpg_sig_header) &&
                         line[gpg_sig_header_len] == ' ')
                        sig = line + gpg_sig_header_len + 1;
                if (sig) {
                        strbuf_add(signature, sig, next - sig);
                        saw_signature = 1;
                        in_signature = 1;
                } else {
                        if (*line == '\n')
                                /* dump the whole remainder of the buffer */
                                next = tail;
                        strbuf_add(payload, line, next - line);
                        in_signature = 0;
                }
                line = next;
        }
 cleanup:
        free(buffer);
        return saw_signature;
}

static void handle_signed_tag(struct commit *parent, struct commit_extra_header ***tail)
{
        struct merge_remote_desc *desc;
        struct commit_extra_header *mergetag;
        char *buf;
        unsigned long size, len;
        enum object_type type;

        desc = merge_remote_util(parent);
        if (!desc || !desc->obj)
                return;
        buf = read_sha1_file(desc->obj->sha1, &type, &size);
        if (!buf || type != OBJ_TAG)
                goto free_return;
        len = parse_signature(buf, size);
        if (size == len)
                goto free_return;
        /*
         * We could verify this signature and either omit the tag when
         * it does not validate, but the integrator may not have the
         * public key of the signer of the tag he is merging, while a
         * later auditor may have it while auditing, so let's not run
         * verify-signed-buffer here for now...
         *
         * if (verify_signed_buffer(buf, len, buf + len, size - len, ...))
         *      warn("warning: signed tag unverified.");
         */
        mergetag = xcalloc(1, sizeof(*mergetag));
        mergetag->key = xstrdup("mergetag");
        mergetag->value = buf;
        mergetag->len = size;

        **tail = mergetag;
        *tail = &mergetag->next;
        return;

free_return:
        free(buf);
}

void append_merge_tag_headers(struct commit_list *parents,
                              struct commit_extra_header ***tail)
{
        while (parents) {
                struct commit *parent = parents->item;
                handle_signed_tag(parent, tail);
                parents = parents->next;
        }
}

static void add_extra_header(struct strbuf *buffer,
                             struct commit_extra_header *extra)
{
        strbuf_addstr(buffer, extra->key);
        if (extra->len)
                strbuf_add_lines(buffer, " ", extra->value, extra->len);
        else
                strbuf_addch(buffer, '\n');
}

struct commit_extra_header *read_commit_extra_headers(struct commit *commit,
                                                      const char **exclude)
{
        struct commit_extra_header *extra = NULL;
        unsigned long size;
        enum object_type type;
        char *buffer = read_sha1_file(commit->object.sha1, &type, &size);
        if (buffer && type == OBJ_COMMIT)
                extra = read_commit_extra_header_lines(buffer, size, exclude);
        free(buffer);
        return extra;
}

static inline int standard_header_field(const char *field, size_t len)
{
        return ((len == 4 && !memcmp(field, "tree ", 5)) ||
                (len == 6 && !memcmp(field, "parent ", 7)) ||
                (len == 6 && !memcmp(field, "author ", 7)) ||
                (len == 9 && !memcmp(field, "committer ", 10)) ||
                (len == 8 && !memcmp(field, "encoding ", 9)));
}

static int excluded_header_field(const char *field, size_t len, const char **exclude)
{
        if (!exclude)
                return 0;

        while (*exclude) {
                size_t xlen = strlen(*exclude);
                if (len == xlen &&
                    !memcmp(field, *exclude, xlen) && field[xlen] == ' ')
                        return 1;
                exclude++;
        }
        return 0;
}

static struct commit_extra_header *read_commit_extra_header_lines(
        const char *buffer, size_t size,
        const char **exclude)
{
        struct commit_extra_header *extra = NULL, **tail = &extra, *it = NULL;
        const char *line, *next, *eof, *eob;
        struct strbuf buf = STRBUF_INIT;

        for (line = buffer, eob = line + size;
             line < eob && *line != '\n';
             line = next) {
                next = memchr(line, '\n', eob - line);
                next = next ? next + 1 : eob;
                if (*line == ' ') {
                        /* continuation */
                        if (it)
                                strbuf_add(&buf, line + 1, next - (line + 1));
                        continue;
                }
                if (it)
                        it->value = strbuf_detach(&buf, &it->len);
                strbuf_reset(&buf);
                it = NULL;

                eof = strchr(line, ' ');
                if (next <= eof)
                        eof = next;

                if (standard_header_field(line, eof - line) ||
                    excluded_header_field(line, eof - line, exclude))
                        continue;

                it = xcalloc(1, sizeof(*it));
                it->key = xmemdupz(line, eof-line);
                *tail = it;
                tail = &it->next;
                if (eof + 1 < next)
                        strbuf_add(&buf, eof + 1, next - (eof + 1));
        }
        if (it)
                it->value = strbuf_detach(&buf, &it->len);
        return extra;
}

void free_commit_extra_headers(struct commit_extra_header *extra)
{
        while (extra) {
                struct commit_extra_header *next = extra->next;
                free(extra->key);
                free(extra->value);
                free(extra);
                extra = next;
        }
}

int commit_tree(const struct strbuf *msg, unsigned char *tree,
                struct commit_list *parents, unsigned char *ret,
                const char *author, const char *sign_commit)
{
        struct commit_extra_header *extra = NULL, **tail = &extra;
        int result;

        append_merge_tag_headers(parents, &tail);
        result = commit_tree_extended(msg, tree, parents, ret,
                                      author, sign_commit, extra);
        free_commit_extra_headers(extra);
        return result;
}

static int find_invalid_utf8(const char *buf, int len)
{
        int offset = 0;

        while (len) {
                unsigned char c = *buf++;
                int bytes, bad_offset;

                len--;
                offset++;

                /* Simple US-ASCII? No worries. */
                if (c < 0x80)
                        continue;

                bad_offset = offset-1;

                /*
                 * Count how many more high bits set: that's how
                 * many more bytes this sequence should have.
                 */
                bytes = 0;
                while (c & 0x40) {
                        c <<= 1;
                        bytes++;
                }

                /* Must be between 1 and 5 more bytes */
                if (bytes < 1 || bytes > 5)
                        return bad_offset;

                /* Do we *have* that many bytes? */
                if (len < bytes)
                        return bad_offset;

                offset += bytes;
                len -= bytes;

                /* And verify that they are good continuation bytes */
                do {
                        if ((*buf++ & 0xc0) != 0x80)
                                return bad_offset;
                } while (--bytes);

                /* We could/should check the value and length here too */
        }
        return -1;
}

/*
 * This verifies that the buffer is in proper utf8 format.
 *
 * If it isn't, it assumes any non-utf8 characters are Latin1,
 * and does the conversion.
 *
 * Fixme: we should probably also disallow overlong forms and
 * invalid characters. But we don't do that currently.
 */
static int verify_utf8(struct strbuf *buf)
{
        int ok = 1;
        long pos = 0;

        for (;;) {
                int bad;
                unsigned char c;
                unsigned char replace[2];

                bad = find_invalid_utf8(buf->buf + pos, buf->len - pos);
                if (bad < 0)
                        return ok;
                pos += bad;
                ok = 0;
                c = buf->buf[pos];
                strbuf_remove(buf, pos, 1);

                /* We know 'c' must be in the range 128-255 */
                replace[0] = 0xc0 + (c >> 6);
                replace[1] = 0x80 + (c & 0x3f);
                strbuf_insert(buf, pos, replace, 2);
                pos += 2;
        }
}

static const char commit_utf8_warn[] =
"Warning: commit message did not conform to UTF-8.\n"
"You may want to amend it after fixing the message, or set the config\n"
"variable i18n.commitencoding to the encoding your project uses.\n";

int commit_tree_extended(const struct strbuf *msg, unsigned char *tree,
                         struct commit_list *parents, unsigned char *ret,
                         const char *author, const char *sign_commit,
                         struct commit_extra_header *extra)
{
        int result;
        int encoding_is_utf8;
        struct strbuf buffer;

        assert_sha1_type(tree, OBJ_TREE);

        if (memchr(msg->buf, '\0', msg->len))
                return error("a NUL byte in commit log message not allowed.");

        /* Not having i18n.commitencoding is the same as having utf-8 */
        encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);

        strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
        strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));

        /*
         * NOTE! This ordering means that the same exact tree merged with a
         * different order of parents will be a _different_ changeset even
         * if everything else stays the same.
         */
        while (parents) {
                struct commit_list *next = parents->next;
                struct commit *parent = parents->item;

                strbuf_addf(&buffer, "parent %s\n",
                            sha1_to_hex(parent->object.sha1));
                free(parents);
                parents = next;
        }

        /* Person/date information */
        if (!author)
                author = git_author_info(IDENT_STRICT);
        strbuf_addf(&buffer, "author %s\n", author);
        strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
        if (!encoding_is_utf8)
                strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);

        while (extra) {
                add_extra_header(&buffer, extra);
                extra = extra->next;
        }
        strbuf_addch(&buffer, '\n');

        /* And add the comment */
        strbuf_addbuf(&buffer, msg);

        /* And check the encoding */
        if (encoding_is_utf8 && !verify_utf8(&buffer))
                fprintf(stderr, commit_utf8_warn);

        if (sign_commit && do_sign_commit(&buffer, sign_commit))
                return -1;

        result = write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
        strbuf_release(&buffer);
        return result;
}

struct commit *get_merge_parent(const char *name)
{
        struct object *obj;
        struct commit *commit;
        unsigned char sha1[20];
        if (get_sha1(name, sha1))
                return NULL;
        obj = parse_object(sha1);
        commit = (struct commit *)peel_to_type(name, 0, obj, OBJ_COMMIT);
        if (commit && !commit->util) {
                struct merge_remote_desc *desc;
                desc = xmalloc(sizeof(*desc));
                desc->obj = obj;
                desc->name = strdup(name);
                commit->util = desc;
        }
        return commit;
}

/*
 * Append a commit to the end of the commit_list.
 *
 * next starts by pointing to the variable that holds the head of an
 * empty commit_list, and is updated to point to the "next" field of
 * the last item on the list as new commits are appended.
 *
 * Usage example:
 *
 *     struct commit_list *list;
 *     struct commit_list **next = &list;
 *
 *     next = commit_list_append(c1, next);
 *     next = commit_list_append(c2, next);
 *     assert(commit_list_count(list) == 2);
 *     return list;
 */
struct commit_list **commit_list_append(struct commit *commit,
                                        struct commit_list **next)
{
        struct commit_list *new = xmalloc(sizeof(struct commit_list));
        new->item = commit;
        *next = new;
        new->next = NULL;
        return &new->next;
}

void print_commit_list(struct commit_list *list,
                       const char *format_cur,
                       const char *format_last)
{
        for ( ; list; list = list->next) {
                const char *format = list->next ? format_cur : format_last;
                printf(format, sha1_to_hex(list->item->object.sha1));
        }
}