Revert "git-gui: set GIT_DIR and GIT_WORK_TREE after setup"

[git/dscho.git] / line.c

#include "cache.h"
#include "tag.h"
#include "blob.h"
#include "tree.h"
#include "diff.h"
#include "commit.h"
#include "decorate.h"
#include "revision.h"
#include "xdiff-interface.h"
#include "strbuf.h"
#include "log-tree.h"
#include "graph.h"
#include "line.h"

static int limited;

static void cleanup(struct diff_line_range *r)
{
        while (r) {
                struct diff_line_range *next = r->next;
                DIFF_LINE_RANGE_CLEAR(r);
                free(r);
                r = next;
        }
}

static struct object *verify_commit(struct rev_info *revs)
{
        struct object *commit = NULL;
        int found = -1;
        int i;

        for (i = 0; i < revs->pending.nr; i++) {
                struct object *obj = revs->pending.objects[i].item;
                if (obj->flags & UNINTERESTING)
                        continue;
                while (obj->type == OBJ_TAG)
                        obj = deref_tag(obj, NULL, 0);
                if (obj->type != OBJ_COMMIT)
                        die("Non commit %s?", revs->pending.objects[i].name);
                if (commit)
                        die("More than one commit to dig from: %s and %s?",
                            revs->pending.objects[i].name,
                                revs->pending.objects[found].name);
                commit = obj;
                found = i;
        }

        if (commit == NULL)
                die("No commit specified?");

        return commit;
}

static void fill_blob_sha1(struct commit *commit, struct diff_line_range *r)
{
        unsigned mode;
        unsigned char sha1[20];

        while (r) {
                if (get_tree_entry(commit->object.sha1, r->spec->path,
                        sha1, &mode))
                        goto error;
                fill_filespec(r->spec, sha1, mode);
                r = r->next;
        }

        return;
error:
        die("There is no path %s in the commit", r->spec->path);
}

static void fill_line_ends(struct diff_filespec *spec, long *lines,
        unsigned long **line_ends)
{
        int num = 0, size = 50;
        long cur = 0;
        unsigned long *ends = NULL;
        char *data = NULL;

        if (diff_populate_filespec(spec, 0))
                die("Cannot read blob %s", sha1_to_hex(spec->sha1));

        ends = xmalloc(size * sizeof(*ends));
        ends[cur++] = 0;
        data = spec->data;
        while (num < spec->size) {
                if (data[num] == '\n' || num == spec->size - 1) {
                        ALLOC_GROW(ends, (cur + 1), size);
                        ends[cur++] = num;
                }
                num++;
        }

        /* shrink the array to fit the elements */
        ends = xrealloc(ends, cur * sizeof(*ends));
        *lines = cur;
        *line_ends = ends;
}

struct nth_line_cb {
        struct diff_filespec *spec;
        long lines;
        unsigned long *line_ends;
};

static const char *nth_line(void *data, long line)
{
        struct nth_line_cb *d = data;
        assert(d && line < d->lines);
        assert(d->spec && d->spec->data);

        if (line == 0)
                return (char *)d->spec->data;
        else
                return (char *)d->spec->data + d->line_ends[line] + 1;
}

/*
 * Parsing of (comma separated) one item in the -L option
 */
const char *parse_loc(const char *spec, nth_line_fn_t nth_line,
                void *data, long lines, long begin, long *ret)
{
        char *term;
        const char *line;
        long num;
        int reg_error;
        regex_t regexp;
        regmatch_t match[1];

        /* Catch the '$' matcher, now it is used to match the last
         * line of the file. */
        if (spec[0] == '$') {
                *ret = lines;
                return spec + 1;
        }

        /* Allow "-L <something>,+20" to mean starting at <something>
         * for 20 lines, or "-L <something>,-5" for 5 lines ending at
         * <something>.
         */
        if (1 < begin && (spec[0] == '+' || spec[0] == '-')) {
                num = strtol(spec + 1, &term, 10);
                if (term != spec + 1) {
                        if (spec[0] == '-')
                                num = 0 - num;
                        if (0 < num)
                                *ret = begin + num - 2;
                        else if (!num)
                                *ret = begin;
                        else
                                *ret = begin + num;
                        return term;
                }
                return spec;
        }
        num = strtol(spec, &term, 10);
        if (term != spec) {
                *ret = num;
                return term;
        }
        if (spec[0] != '/')
                return spec;

        /* it could be a regexp of form /.../ */
        for (term = (char *) spec + 1; *term && *term != '/'; term++) {
                if (*term == '\\')
                        term++;
        }
        if (*term != '/')
                return spec;

        /* try [spec+1 .. term-1] as regexp */
        *term = 0;
        begin--; /* input is in human terms */
        line = nth_line(data, begin);

        if (!(reg_error = regcomp(&regexp, spec + 1, REG_NEWLINE)) &&
            !(reg_error = regexec(&regexp, line, 1, match, 0))) {
                const char *cp = line + match[0].rm_so;
                const char *nline;

                while (begin++ < lines) {
                        nline = nth_line(data, begin);
                        if (line <= cp && cp < nline)
                                break;
                        line = nline;
                }
                *ret = begin;
                regfree(&regexp);
                *term++ = '/';
                return term;
        } else {
                char errbuf[1024];
                regerror(reg_error, &regexp, errbuf, 1024);
                die("-L parameter '%s': %s", spec + 1, errbuf);
        }
}

static void parse_range(long lines, unsigned long *line_ends,
                struct line_range *r, struct diff_filespec *spec)
{
        const char *term;
        struct nth_line_cb data = {spec, lines, line_ends};

        term = parse_loc(r->arg, nth_line, &data, lines - 1, 1, &r->start);
        if (*term == ',') {
                term = parse_loc(term + 1, nth_line, &data, lines - 1,
                        r->start + 1, &r->end);
                if (*term)
                        die("-L parameter's argument should be <start>,<end>");
        }

        if (*term)
                die("-L parameter's argument should be <start>,<end>");

        if (r->start < 1)
                r->start = 1;
        if (r->end >= lines)
                r->end = lines - 1;

        if (r->start > r->end) {
                long tmp = r->start;
                r->start = r->end;
                r->end = tmp;
        }
}

static void parse_lines(struct commit *commit, struct diff_line_range *r)
{
        int i;
        struct line_range *old_range = NULL;
        long lines = 0;
        unsigned long *ends = NULL;

        while (r) {
                struct diff_filespec *spec = r->spec;
                int num = r->nr;
                assert(spec);
                fill_blob_sha1(commit, r);
                old_range = r->ranges;
                r->ranges = NULL;
                r->nr = r->alloc = 0;
                fill_line_ends(spec, &lines, &ends);
                for (i = 0; i < num; i++) {
                        parse_range(lines, ends, old_range + i, spec);
                        diff_line_range_insert(r, old_range[i].arg,
                                old_range[i].start, old_range[i].end);
                }

                free(ends);
                ends = NULL;

                r = r->next;
                free(old_range);
        }
}

/*
 * Insert a new line range into a diff_line_range struct, and keep the
 * r->ranges sorted by their starting line number.
 */
struct line_range *diff_line_range_insert(struct diff_line_range *r,
                const char *arg, int start, int end)
{
        int i = 0;
        struct line_range *rs = r->ranges;
        int left_merge = 0, right_merge = 0;

        assert(r != NULL);
        assert(start <= end);

        if (r->nr == 0 || rs[r->nr - 1].end < start - 1) {
                int num = 0;
                DIFF_LINE_RANGE_GROW(r);
                rs = r->ranges;
                num = r->nr - 1;
                rs[num].arg = arg;
                rs[num].start = start;
                rs[num].end = end;
                return rs + num;
        }

        for (; i < r->nr; i++) {
                if (rs[i].end < start - 1)
                        continue;
                if (rs[i].end == start - 1) {
                        rs[i].end = end;
                        right_merge = 1;
                        goto out;
                }

                assert(rs[i].end > start - 1);
                if (rs[i].start <= start) {
                        if (rs[i].end < end) {
                                rs[i].end = end;
                                right_merge = 1;
                        }
                        goto out;
                } else if (rs[i].start <= end + 1) {
                        rs[i].start = start;
                        left_merge = 1;
                        if (rs[i].end < end) {
                                rs[i].end = end;
                                right_merge = 1;
                        }
                        goto out;
                } else {
                        int num = r->nr - i;
                        DIFF_LINE_RANGE_GROW(r);
                        rs = r->ranges;
                        memmove(rs + i + 1, rs + i, num * sizeof(struct line_range));
                        rs[i].arg = arg;
                        rs[i].start = start;
                        rs[i].end = end;
                        goto out;
                }
        }

out:
        assert(r->nr != i);
        if (left_merge) {
                int j = i;
                for (; j > -1; j--) {
                        if (rs[j].end >= rs[i].start - 1)
                                if (rs[j].start < rs[i].start)
                                        rs[i].start = rs[j].start;
                }
                memmove(rs + j + 1, rs + i, (r->nr - i) * sizeof(struct line_range));
                r->nr -= i - j - 1;
        }
        if (right_merge) {
                int j = i;
                for (; j < r->nr; j++) {
                        if (rs[j].start <= rs[i].end + 1)
                                if (rs[j].end > rs[i].end)
                                        rs[i].end = rs[j].end;
                }
                if (j < r->nr)
                        memmove(rs + i + 1, rs + j, (r->nr - j) * sizeof(struct line_range));
                r->nr -= j - i - 1;
        }
        assert(r->nr);

        return rs + i;
}

void diff_line_range_clear(struct diff_line_range *r)
{
        int i = 0, zero = 0;

        for (; i < r->nr; i++) {
                struct line_range *rg = r->ranges + i;
                RANGE_CLEAR(rg);
        }

        if (r->prev) {
                zero = 0;
                if (r->prev->count == 1)
                        zero = 1;
                free_filespec(r->prev);
                if (zero)
                        r->prev = NULL;
        }
        if (r->spec) {
                zero = 0;
                if (r->spec->count == 1)
                        zero = 1;
                free_filespec(r->spec);
                if (zero)
                        r->spec = NULL;
        }

        r->status = '\0';
        r->alloc = r->nr = 0;

        if (r->ranges)
                free(r->ranges);
        r->ranges = NULL;
        r->next = NULL;
}

void diff_line_range_append(struct diff_line_range *r, const char *arg)
{
        DIFF_LINE_RANGE_GROW(r);
        r->ranges[r->nr - 1].arg = arg;
}

struct diff_line_range *diff_line_range_clone(struct diff_line_range *r)
{
        struct diff_line_range *ret = xmalloc(sizeof(*ret));
        int i = 0;

        assert(r);
        DIFF_LINE_RANGE_INIT(ret);
        ret->ranges = xcalloc(r->nr, sizeof(struct line_range));
        memcpy(ret->ranges, r->ranges, sizeof(struct line_range) * r->nr);

        ret->alloc = ret->nr = r->nr;

        for (; i < ret->nr; i++)
                PRINT_PAIR_INIT(&ret->ranges[i].pair);

        ret->spec = r->spec;
        assert(ret->spec);
        ret->spec->count++;

        return ret;
}

struct diff_line_range *diff_line_range_clone_deeply(struct diff_line_range *r)
{
        struct diff_line_range *ret = NULL;
        struct diff_line_range *tmp = NULL, *prev = NULL;

        assert(r);
        ret = tmp = prev = diff_line_range_clone(r);
        r = r->next;
        while (r) {
                tmp = diff_line_range_clone(r);
                prev->next = tmp;
                prev = tmp;
                r = r->next;
        }

        return ret;
}

struct diff_line_range *diff_line_range_merge(struct diff_line_range *out,
                struct diff_line_range *other)
{
        struct diff_line_range *one = out, *two = other;
        struct diff_line_range *pone = NULL;

        while (one) {
                struct diff_line_range *ptwo;
                two = other;
                ptwo = other;
                while (two) {
                        if (!strcmp(one->spec->path, two->spec->path)) {
                                int i = 0;
                                for (; i < two->nr; i++) {
                                        diff_line_range_insert(one, NULL,
                                                two->ranges[i].start,
                                                two->ranges[i].end);
                                }
                                if (two == other)
                                        other = other->next;
                                else
                                        ptwo->next = two->next;
                                DIFF_LINE_RANGE_CLEAR(two);
                                free(two);
                                two = NULL;

                                break;
                        }

                        ptwo = two;
                        two = two->next;
                }

                pone = one;
                one = one->next;
        }
        pone->next = other;

        return out;
}

void add_line_range(struct rev_info *revs, struct commit *commit,
                struct diff_line_range *r)
{
        struct diff_line_range *ret = NULL;

        ret = lookup_decoration(&revs->line_range, &commit->object);
        if (ret != NULL && r != NULL)
                diff_line_range_merge(ret, r);
        else
                add_decoration(&revs->line_range, &commit->object, r);

        if (r != NULL)
                commit->object.flags |= RANGE_UPDATE;
}

struct diff_line_range *lookup_line_range(struct rev_info *revs,
                struct commit *commit)
{
        struct diff_line_range *ret = NULL;

        ret = lookup_decoration(&revs->line_range, &commit->object);
        return ret;
}

void setup_line(struct rev_info *rev, struct diff_line_range *r)
{
        struct commit *commit = NULL;
        struct diff_options *opt = &rev->diffopt;

        commit = (struct commit *)verify_commit(rev);
        parse_lines(commit, r);

        add_line_range(rev, commit, r);
        /*
         * Note we support -M/-C to detect file rename
         */
        opt->nr_paths = 0;
        diff_tree_release_paths(opt);
}

struct take_range_cb_data {
        struct diff_line_range *interesting;    /* currently interesting ranges */
        struct diff_line_range *range;
                /* the ranges corresponds to the interesting ranges of parent commit */
        long plno, tlno;
                /* the last line number of diff hunk */
        int diff;
                /* whether there is some line changes between the current
                 * commit and its parent */
};

#define SCALE_FACTOR 4
/*
 * [p_start, p_end] represents the pre-image of current diff hunk,
 * [t_start, t_end] represents the post-image of the current diff hunk,
 * [start, end] represents the currently interesting line range in
 * post-image,
 * [o_start, o_end] represents the original line range that coresponds
 * to current line range.
 */
void map_lines(long p_start, long p_end, long t_start, long t_end,
                long start, long end, long *o_start, long *o_end)
{
        /*
         * Normally, p_start should be less than p_end, so does the
         * t_start and t_end. But when the line range is added from
         * scratch, p_start will be greater than p_end. When the line
         * range is deleted, t_start will be greater than t_end.
         */
        if (p_start > p_end) {
                *o_start = *o_end = 0;
                return;
        }
        /* A deletion */
        if (t_start > t_end) {
                *o_start = p_start;
                *o_end = p_end;
                return;
        }

        if (start == t_start && end == t_end) {
                *o_start = p_start;
                *o_end = p_end;
                return;
        }

        if (start == t_start) {
                *o_start = p_start;
                *o_end = p_start + (end - start);
                if (*o_end > p_end)
                        *o_end = p_end;
                return;
        }

        if (end == t_end) {
                *o_start = p_end - (end - start);
                if (*o_start < p_start)
                        *o_start = p_start;
                *o_end = p_end;
                return;
        }

        /*
         * A heuristic for lines mapping:
         *
         * When the pre-image is no more than 1/SCALE_FACTOR of the post-image,
         * there is no effective way to find out which part of pre-image
         * corresponds to the currently interesting range of post-image.
         * And we are in the danger of tracking totally useless lines.
         * So, we just treat all the post-image lines as added from scratch.
         */
        if (SCALE_FACTOR * (p_end - p_start + 1) < (t_end - t_start + 1)) {
                *o_start = *o_end = 0;
                return;
        }

        *o_start = p_start + start - t_start;
        *o_end = p_end - (t_end - end);

        if (*o_start > *o_end) {
                int temp = *o_start;
                *o_start = *o_end;
                *o_end = temp;
        }

        if (*o_start < p_start)
                *o_start = p_start;
        if (*o_end > p_end)
                *o_end = p_end;
}

/*
 * When same == 1:
 * [p_start, p_end] represents the diff hunk line range of pre-image,
 * [t_start, t_end] represents the diff hunk line range of post-image.
 * When same == 0, they represent a range of identical lines between
 * two images.
 *
 * This function find out the corresponding line ranges of currently
 * interesting ranges which this diff hunk touches.
 */
static void map_range(struct take_range_cb_data *data, int same,
                long p_start, long p_end, long t_start, long t_end)
{
        struct line_range *ranges = data->interesting->ranges;
        long takens, takene, start, end;
        int i = 0, out = 0, added = 0;
        long op_start = p_start, op_end = p_end, ot_start = t_start, ot_end = t_end;

        for (; i < data->interesting->nr; i++) {
                added = 0;
                if (t_start > ranges[i].end)
                        continue;
                if (t_end < ranges[i].start)
                        break;

                if (t_start > ranges[i].start) {
                        start = t_start;
                        takens = p_start;
                        if (t_end >= ranges[i].end) {
                                end = ranges[i].end;
                                takene = p_start + end - t_start;
                        } else {
                                end = t_end;
                                takene = p_end;
                                out = 1;
                        }
                } else {
                        start = ranges[i].start;
                        takens = p_start + start - t_start;
                        if (t_end >= ranges[i].end) {
                                end = ranges[i].end;
                                takene = p_start + end - t_start;
                        } else {
                                end = t_end;
                                takene = p_end;
                                out = 1;
                        }
                }

                if (!same) {
                        struct print_pair *pair = &ranges[i].pair;
                        struct print_range *rr = NULL;
                        PRINT_PAIR_GROW(pair);
                        rr = pair->ranges + pair->nr - 1;
                        PRINT_RANGE_INIT(rr);
                        rr->start = start;
                        rr->end = end;
                        map_lines(op_start, op_end, ot_start, ot_end, start, end,
                                        &takens, &takene);
                        if (takens == 0 && takene == 0) {
                                added = 1;
                                rr->line_added = 1;
                        }
                        rr->pstart = takens;
                        rr->pend = takene;
                        data->diff = 1;
                        data->interesting->diff = 1;
                        ranges[i].diff = 1;
                }
                if (added) {
                        /* Code movement/copy detect here, now place two dummy statements here */
                        int dummy = 0;
                        dummy = 1;
                } else {
                        struct line_range *added_range = diff_line_range_insert(data->range,
                                        NULL, takens, takene);
                        assert(added_range);
                        ranges[i].pstart = added_range->start;
                        ranges[i].pend = added_range->end;
                }

                t_start = end + 1;
                p_start = takene + 1;

                if (out)
                        break;
        }
}

/*
 * [p_start, p_end] represents the line range of pre-image,
 * [t_start, t_end] represents the line range of post-image,
 * and they are identical lines.
 *
 * This function substracts out the identical lines between current
 * commit and its parent, from currently interesting ranges.
 */
static void take_range(struct take_range_cb_data *data,
                long p_start, long p_end, long t_start, long t_end)
{
        struct line_range *ranges = data->interesting->ranges;
        long takens, takene, start, end;
        int i = 0, out = 0, added = 0;

        for (; i < data->interesting->nr; i++) {
                added = 0;
                if (t_start > ranges[i].end)
                        continue;
                if (t_end < ranges[i].start)
                        break;

                if (t_start > ranges[i].start) {
                        long tmp = ranges[i].end;
                        ranges[i].end = t_start - 1;
                        start = t_start;
                        takens = p_start;
                        if (t_end >= tmp) {
                                end = tmp;
                                takene = p_start + end - t_start;
                                p_start = takene + 1;
                                t_start = end + 1;
                        } else {
                                end = t_end;
                                takene = p_end;
                                diff_line_range_insert(data->interesting, NULL,
                                        t_end + 1, tmp);
                                out = 1;
                        }
                } else {
                        start = ranges[i].start;
                        takens = p_start + start - t_start;
                        if (t_end >= ranges[i].end) {
                                int num = data->interesting->nr - 1;
                                end = ranges[i].end;
                                takene = p_start + end - t_start;
                                t_start = end + 1;
                                p_start = takene + 1;
                                memmove(ranges + i, ranges + i + 1, (num - i) * sizeof(*ranges));
                                data->interesting->nr = num;
                                i--;
                        } else {
                                end = t_end;
                                takene = p_end;
                                ranges[i].start = t_end + 1;
                                out = 1;
                        }
                }

                diff_line_range_insert(data->range, NULL, takens, takene);

                if (out)
                        break;
        }
}

static void take_range_cb(void *data, long same, long p_next, long t_next)
{
        struct take_range_cb_data *d = data;
        long p_start = d->plno + 1, t_start = d->tlno + 1;
        long p_end = p_start + same - t_start, t_end = same;

        /* If one file is added from scratch, we should not bother to call
         * take_range, since there is nothing to take
         */
        if (t_end >= t_start)
                take_range(d, p_start, p_end, t_start, t_end);
        d->plno = p_next;
        d->tlno = t_next;
}

static void map_range_cb(void *data, long same, long p_next, long t_next)
{
        struct take_range_cb_data *d = data;

        long p_start = d->plno + 1;
        long t_start = d->tlno + 1;
        long p_end = same - t_start + p_start;
        long t_end = same;

        /* Firstly, take the unchanged lines from child */
        if (t_end >= t_start)
                map_range(d, 1, p_start, p_end, t_start, t_end);

        /* find out which lines to print */
        t_start = same + 1;
        p_start = d->plno + t_start - d->tlno;
        map_range(d, 0, p_start, p_next, t_start, t_next);

        d->plno = p_next;
        d->tlno = t_next;
}

/*
 * We support two kinds of operation in this function:
 * 1. map == 0, take the same lines from the current commit and assign it
 *              to parent;
 * 2. map == 1, in addition to the same lines, we also map the changed lines
 *              from the current commit to the parent according to the
 *              diff output.
 * take_range_cb and take_range are used to take same lines from current commit
 * to parents.
 * map_range_cb and map_range are used to map line ranges to the parent.
 */
static int assign_range_to_parent(struct rev_info *rev, struct commit *c,
                struct commit *p, struct diff_line_range *r,
                struct diff_options *opt, int map)
{
        struct diff_line_range *rr = xmalloc(sizeof(*rr));
        struct diff_line_range *cr = rr, *prev_r = rr;
        struct diff_line_range *rg = NULL;
        struct tree_desc desc1, desc2;
        void *tree1 = NULL, *tree2 = NULL;
        unsigned long size1, size2;
        struct diff_queue_struct *queue;
        struct take_range_cb_data cb = {NULL, cr, 0, 0};
        xpparam_t xpp;
        xdemitconf_t xecfg;
        int i, diff = 0;
        xdiff_emit_hunk_consume_fn fn = map ? map_range_cb : take_range_cb;

        DIFF_LINE_RANGE_INIT(cr);
        memset(&xpp, 0, sizeof(xpp));
        memset(&xecfg, 0, sizeof(xecfg));
        xecfg.ctxlen = xecfg.interhunkctxlen = 0;

        /*
         * Compose up two trees, for root commit, we make up a empty tree.
         */
        assert(c);
        tree2 = read_object_with_reference(c->tree->object.sha1, "tree",
                        &size2, NULL);
        if (tree2 == NULL)
                die("Unable to read tree (%s)", sha1_to_hex(c->tree->object.sha1));
        init_tree_desc(&desc2, tree2, size2);
        if (p) {
                tree1 = read_object_with_reference(p->tree->object.sha1,
                                "tree", &size1, NULL);
                if (tree1 == NULL)
                        die("Unable to read tree (%s)",
                                        sha1_to_hex(p->tree->object.sha1));
                init_tree_desc(&desc1, tree1, size1);
        } else {
                init_tree_desc(&desc1, "", 0);
        }

        DIFF_QUEUE_CLEAR(&diff_queued_diff);
        diff_tree(&desc1, &desc2, "", opt);
        diffcore_std(opt);

        queue = &diff_queued_diff;
        for (i = 0; i < queue->nr; i++) {
                struct diff_filepair *pair = queue->queue[i];
                struct diff_line_range *rg = r;
                mmfile_t file_p, file_t;
                assert(pair->two->path);
                while (rg) {
                        assert(rg->spec->path);
                        if (!strcmp(rg->spec->path, pair->two->path))
                                break;
                        rg = rg->next;
                }

                if (rg == NULL)
                        continue;
                rg->touch = 1;
                if (rg->nr == 0)
                        continue;

                rg->status = pair->status;
                assert(pair->two->sha1_valid);
                diff_populate_filespec(pair->two, 0);
                file_t.ptr = pair->two->data;
                file_t.size = pair->two->size;

                if (rg->prev)
                        free_filespec(rg->prev);
                rg->prev = pair->one;
                rg->prev->count++;
                if (pair->one->sha1_valid) {
                        diff_populate_filespec(pair->one, 0);
                        file_p.ptr = pair->one->data;
                        file_p.size = pair->one->size;
                } else {
                        file_p.ptr = "";
                        file_p.size = 0;
                }

                if (cr->nr != 0) {
                        struct diff_line_range *tmp = xmalloc(sizeof(*tmp));
                        cr->next = tmp;
                        prev_r = cr;
                        cr = tmp;
                } else if (cr->spec)
                        DIFF_LINE_RANGE_CLEAR(cr);

                DIFF_LINE_RANGE_INIT(cr);
                if (pair->one->sha1_valid) {
                        cr->spec = pair->one;
                        cr->spec->count++;
                }

                cb.interesting = rg;
                cb.range = cr;
                cb.diff = 0;
                cb.plno = cb.tlno = 0;
                xdi_diff_hunks(&file_p, &file_t, fn, &cb, &xpp, &xecfg);
                if (cb.diff)
                        diff = 1;
                /*
                 * The remain part is the same part.
                 * Instead of calculating the true line number of the two files,
                 * use the biggest integer.
                 */
                if (map)
                        map_range(&cb, 1, cb.plno + 1, INT_MAX, cb.tlno + 1, INT_MAX);
                else
                        take_range(&cb, cb.plno + 1, INT_MAX, cb.tlno + 1, INT_MAX);
        }
        opt->output_format = DIFF_FORMAT_NO_OUTPUT;
        diff_flush(opt);

        /*
         * Collect the untouch ranges, this comes from the files not changed
         * between two commit.
         */
        rg = r;
        while (rg) {
                /* clear the touch one to make it usable in next round */
                if (rg->touch) {
                        rg->touch = 0;
                } else {
                        struct diff_line_range *untouch = diff_line_range_clone(rg);
                        if (prev_r == rr && rr->nr == 0) {
                                rr = prev_r = untouch;
                        } else {
                                prev_r->next = untouch;
                                prev_r = untouch;
                        }
                }
                rg = rg->next;
        }

        if (cr->nr == 0) {
                DIFF_LINE_RANGE_CLEAR(cr);
                free(cr);
                if (prev_r == cr)
                        rr = NULL;
                else
                        prev_r->next = NULL;
        }

        if (!map)
                goto out;

        if (rr) {
                assert(p);
                add_line_range(rev, p, rr);
        } else {
                /*
                 * If there is no new ranges assigned to the parent,
                 * we should mark it as a 'root' commit.
                 */
                if (c->parents && !c->parents->next) {
                        free(c->parents);
                        c->parents = NULL;
                }
        }

        /* and the ranges of current commit c is updated */
        c->object.flags &= ~RANGE_UPDATE;
        if (diff)
                c->object.flags |= NEED_PRINT;

out:
        if (tree1)
                free(tree1);
        if (tree2)
                free(tree2);

        return diff;
}

static void diff_update_parent_range(struct rev_info *rev,
                struct commit *commit)
{
        struct diff_line_range *r = lookup_line_range(rev, commit);
        struct commit_list *parents = commit->parents;
        struct commit *c = NULL;
        if (parents) {
                assert(parents->next == NULL);
                c = parents->item;
        }

        assign_range_to_parent(rev, commit, c, r, &rev->diffopt, 1);
}

struct commit_state {
        struct diff_line_range *range;
        struct object obj;
};

static void assign_parents_range(struct rev_info *rev, struct commit *commit)
{
        struct commit_list *parents = commit->parents;
        struct diff_line_range *r = lookup_line_range(rev, commit);
        struct diff_line_range *evil = NULL, *range = NULL;
        struct decoration parents_state;
        struct commit_state *state = NULL;
        int nontrivial = 0;

        memset(&parents_state, 0, sizeof(parents_state));
        /*
         * If we are in linear history, update range and flush the patch if
         * necessary
         */
        if (parents == NULL || parents->next == NULL)
                return diff_update_parent_range(rev, commit);

        /*
         * Loop on the parents and assign the ranges to different
         * parents, if there is any range left, this commit must
         * be an evil merge.
         */
        evil = diff_line_range_clone_deeply(r);
        parents = commit->parents;
        while (parents) {
                struct commit *p = parents->item;
                int diff = 0;
                struct diff_line_range *origin_range = lookup_line_range(rev, p);
                if (origin_range)
                        origin_range = diff_line_range_clone_deeply(origin_range);

                state = xmalloc(sizeof(*state));
                state->range = origin_range;
                state->obj = p->object;
                add_decoration(&parents_state, &p->object, state);
                diff = assign_range_to_parent(rev, commit, p, r, &rev->diffopt, 1);
                /* Since all the ranges comes from this parent, we can ignore others */
                if (diff == 0) {
                        /* restore the state of parents before this one */
                        parents = commit->parents;
                        while (parents->item != p) {
                                struct commit_list *list = parents;
                                struct diff_line_range *line_range = NULL;
                                parents = parents->next;
                                line_range = lookup_line_range(rev, list->item);
                                cleanup(line_range);
                                state = lookup_decoration(&parents_state, &list->item->object);
                                add_decoration(&parents_state, &list->item->object, NULL);
                                add_line_range(rev, list->item, state->range);
                                list->item->object = state->obj;
                                free(state);
                                free(list);
                        }

                        commit->parents = parents;
                        parents = parents->next;
                        commit->parents->next = NULL;

                        /* free the non-use commit_list */
                        while (parents) {
                                struct commit_list *list = parents;
                                parents = parents->next;
                                free(list);
                        }
                        goto out;
                }
                /* take the ranges from 'commit', try to detect nontrivial merge */
                assign_range_to_parent(rev, commit, p, evil, &rev->diffopt, 0);
                parents = parents->next;
        }

        commit->object.flags |= NONTRIVIAL_MERGE;
        /*
         * yes, this must be an evil merge.
         */
        range = evil;
        while (range) {
                if (range->nr) {
                        commit->object.flags |= EVIL_MERGE;
                        nontrivial = 1;
                }
                range = range->next;
        }

out:
        /* Never print out any diff for a merge commit */
        commit->object.flags &= ~NEED_PRINT;

        parents = commit->parents;
        while (parents) {
                state = lookup_decoration(&parents_state, &parents->item->object);
                if (state) {
                        cleanup(state->range);
                        free(state);
                }
                parents = parents->next;
        }

        if (nontrivial)
                add_decoration(&rev->nontrivial_merge, &commit->object, evil);
        else
                cleanup(evil);
}

struct line_chunk {
        int lone, ltwo;
        const char *one, *two;
        const char *one_end, *two_end;
        struct diff_line_range *range;
};

static void flush_lines(struct diff_options *opt, const char **ptr, const char *end,
                int slno, int elno, int *lno, const char *color, const char heading)
{
        const char *p = *ptr;
        struct strbuf buf = STRBUF_INIT;
        const char *reset;
        char *line_prefix = "";
        struct strbuf *msgbuf;

        if (opt && opt->output_prefix) {
                msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
                line_prefix = msgbuf->buf;
        }

        if (*color)
                reset = diff_get_color_opt(opt, DIFF_RESET);
        else
                reset = "";

        strbuf_addf(&buf, "%s%c", color, heading);
        while (*ptr < end && *lno < slno) {
                if (**ptr == '\n') {
                        (*lno)++;
                        if (*lno == slno) {
                                (*ptr)++;
                                break;
                        }
                }
                (*ptr)++;
        }
        assert(*ptr <= end);
        p = *ptr;

        while (*ptr < end && *lno <= elno) {
                if (**ptr == '\n') {
                        fprintf(opt->file, "%s%s", line_prefix, buf.buf);
                        if (*ptr - p)
                                fwrite(p, *ptr - p, 1, opt->file);
                        fprintf(opt->file, "%s\n", reset);
                        p = *ptr + 1;
                        (*lno)++;
                }
                (*ptr)++;
        }
        if (*lno <= elno) {
                fprintf(opt->file, "%s%s", line_prefix, buf.buf);
                if (*ptr - p)
                        fwrite(p, *ptr - p, 1, opt->file);
                fprintf(opt->file, "%s\n", reset);
        }
        strbuf_release(&buf);
}

static void diff_flush_range(struct diff_options *opt, struct line_chunk *chunk,
                struct line_range *range)
{
        struct print_pair *pair = &range->pair;
        const char *old = diff_get_color_opt(opt, DIFF_FILE_OLD);
        const char *new = diff_get_color_opt(opt, DIFF_FILE_NEW);
        int i, cur = range->start;

        for (i = 0; i < pair->nr; i++) {
                struct print_range *pr = pair->ranges + i;
                if (cur < pr->start)
                        flush_lines(opt, &chunk->two, chunk->two_end,
                                cur, pr->start - 1, &chunk->ltwo, "", ' ');

                if (!pr->line_added)
                        flush_lines(opt, &chunk->one, chunk->one_end,
                                pr->pstart, pr->pend, &chunk->lone, old, '-');
                flush_lines(opt, &chunk->two, chunk->two_end,
                        pr->start, pr->end, &chunk->ltwo, new, '+');

                cur = pr->end + 1;
        }

        if (cur <= range->end) {
                flush_lines(opt, &chunk->two, chunk->two_end,
                        cur, range->end, &chunk->ltwo, "", ' ');
        }
}

static void diff_flush_chunks(struct diff_options *opt, struct line_chunk *chunk)
{
        struct diff_line_range *range = chunk->range;
        const char *set = diff_get_color_opt(opt, DIFF_FRAGINFO);
        const char *reset = diff_get_color_opt(opt, DIFF_RESET);
        char *line_prefix = "";
        struct strbuf *msgbuf;
        int i;

        if (opt && opt->output_prefix) {
                msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
                line_prefix = msgbuf->buf;
        }

        for (i = 0; i < range->nr; i++) {
                struct line_range *r = range->ranges + i;
                long lenp = r->pend - r->pstart + 1, pstart = r->pstart;
                long len = r->end - r->start + 1;
                if (pstart == 0)
                        lenp = 0;

                fprintf(opt->file, "%s%s@@ -%ld,%ld +%ld,%ld @@%s\n",
                        line_prefix, set, pstart, lenp, r->start, len, reset);

                diff_flush_range(opt, chunk, r);
        }
}

static void diff_flush_filepair(struct rev_info *rev, struct diff_line_range *range)
{
        struct diff_options *opt = &rev->diffopt;
        struct diff_filespec *one = range->prev, *two = range->spec;
        struct diff_filepair p = {one, two, range->status, 0};
        struct strbuf header = STRBUF_INIT, meta = STRBUF_INIT;
        const char *a_prefix, *b_prefix;
        const char *name_a, *name_b, *a_one, *b_two;
        const char *lbl[2];
        const char *set = diff_get_color_opt(opt, DIFF_METAINFO);
        const char *reset = diff_get_color_opt(opt, DIFF_RESET);
        struct line_chunk chunk;
        int must_show_header;
        char *line_prefix = "";
        struct strbuf *msgbuf;

        if (opt && opt->output_prefix) {
                msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
                line_prefix = msgbuf->buf;
        }

        /*
         * the ranges that touch no different file, in this case
         * the line number will not change, and of course we have
         * no sensible range->pair since there is no diff run.
         */
        if (one == NULL) {
                if (rev->full_line_diff) {
                        chunk.two = two->data;
                        chunk.two_end = (const char *)two->data + two->size;
                        chunk.ltwo = 1;
                        chunk.range = range;
                        diff_flush_chunks(&rev->diffopt, &chunk);
                }
                return;
        }

        if (range->status == DIFF_STATUS_DELETED)
                die("We are following an nonexistent file, interesting!");

        name_a  = one->path;
        name_b = two->path;
        fill_metainfo(&meta, name_a, name_b, one, two, opt, &p, &must_show_header,
                        DIFF_OPT_TST(opt, COLOR_DIFF));

        diff_set_mnemonic_prefix(opt, "a/", "b/");
        if (DIFF_OPT_TST(opt, REVERSE_DIFF)) {
                a_prefix = opt->b_prefix;
                b_prefix = opt->a_prefix;
        } else {
                a_prefix = opt->a_prefix;
                b_prefix = opt->b_prefix;
        }

        name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
        name_b = DIFF_FILE_VALID(two) ? name_b : name_a;

        a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
        b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
        lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
        lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
        strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix,
                        set, a_one, b_two, reset);
        if (lbl[0][0] == '/') {
                strbuf_addf(&header, "%s%snew file mode %06o%s\n",
                        line_prefix, set, two->mode, reset);
        } else if (lbl[1][0] == '/') {
                strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n",
                        line_prefix, set, one->mode, reset);
        } else if (one->mode != two->mode) {
                        strbuf_addf(&header, "%s%sold mode %06o%s\n",
                                line_prefix, set, one->mode, reset);
                        strbuf_addf(&header, "%s%snew mode %06o%s\n",
                                line_prefix, set, two->mode, reset);
        }

        fprintf(opt->file, "%s%s", header.buf, meta.buf);
        strbuf_release(&meta);
        strbuf_release(&header);
        fprintf(opt->file, "%s%s--- %s%s\n", line_prefix, set, lbl[0], reset);
        fprintf(opt->file, "%s%s+++ %s%s\n", line_prefix, set, lbl[1], reset);
        free((void *)a_one);
        free((void *)b_two);

        chunk.one = one->data;
        chunk.one_end = (const char *)one->data + one->size;
        chunk.lone = 1;
        chunk.two = two->data;
        chunk.two_end = (const char *)two->data + two->size;
        chunk.ltwo = 1;
        chunk.range = range;
        diff_flush_chunks(&rev->diffopt, &chunk);
}

#define EVIL_MERGE_STR "nontrivial merge found"
static void flush_nontrivial_merge(struct rev_info *rev,
                struct diff_line_range *range)
{
        struct diff_options *opt = &rev->diffopt;
        const char *reset = diff_get_color_opt(opt, DIFF_RESET);
        const char *frag = diff_get_color_opt(opt, DIFF_FRAGINFO);
        const char *meta = diff_get_color_opt(opt, DIFF_METAINFO);
        const char *new = diff_get_color_opt(opt, DIFF_FILE_NEW);
        char *line_prefix = "";
        struct strbuf *msgbuf;
        int evil = 0;
        struct diff_line_range *r = range;

        if (opt && opt->output_prefix) {
                msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
                line_prefix = msgbuf->buf;
        }

        while (r) {
                if (r->nr)
                        evil = 1;
                r = r->next;
        }

        if (!evil)
                return;

        fprintf(opt->file, "%s%s%s%s\n", line_prefix, meta, EVIL_MERGE_STR, reset);

        while (range) {
                if (range->nr) {
                        int lno = 1;
                        const char *ptr = range->spec->data;
                        const char *end = (const char *)range->spec->data + range->spec->size;
                        int i = 0;
                        fprintf(opt->file, "%s%s%s%s\n", line_prefix,
                                meta, range->spec->path, reset);
                        for (; i < range->nr; i++) {
                                struct line_range *r = range->ranges + i;
                                fprintf(opt->file, "%s%s@@ %ld,%ld @@%s\n",
                                        line_prefix, frag, r->start,
                                        r->end - r->start + 1, reset);
                                flush_lines(opt, &ptr, end, r->start, r->end,
                                        &lno, new, ' ');
                        }
                        fprintf(opt->file, "%s\n", line_prefix);
                }
                range = range->next;
        }
}

static void line_log_flush(struct rev_info *rev, struct commit *c)
{
        struct diff_line_range *range = lookup_line_range(rev, c);
        struct diff_line_range *nontrivial = lookup_decoration(&rev->nontrivial_merge,
                                                        &c->object);
        struct log_info log;
        struct diff_options *opt = &rev->diffopt;
        char *line_prefix = "";
        struct strbuf *msgbuf;

        if (range == NULL || !(c->object.flags & NONTRIVIAL_MERGE ||
                        c->object.flags & NEED_PRINT ||
                        rev->full_line_diff))
                return;

        if (rev->graph)
                graph_update(rev->graph, c);
        log.commit = c;
        log.parent = NULL;
        rev->loginfo = &log;
        show_log(rev);
        rev->loginfo = NULL;

        if (opt && opt->output_prefix) {
                msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
                line_prefix = msgbuf->buf;
        }
        fprintf(rev->diffopt.file, "%s\n", line_prefix);

        if (c->object.flags & NONTRIVIAL_MERGE)
                flush_nontrivial_merge(rev, nontrivial);
        else {
                while (range) {
                        if (range->diff || (range->nr && rev->full_line_diff))
                                diff_flush_filepair(rev, range);
                        range = range->next;
                }
        }

        while (rev->graph && !graph_is_commit_finished(rev->graph)) {
                struct strbuf sb;
                strbuf_init(&sb, 0);
                graph_next_line(rev->graph, &sb);
                fputs(sb.buf, opt->file);
        }
}

int cmd_line_log_walk(struct rev_info *rev)
{
        struct commit *commit;
        struct commit_list *list = NULL;
        struct diff_line_range *r = NULL;

        if (prepare_revision_walk(rev))
                die("revision walk prepare failed");

        list = rev->commits;
        if (list && !limited) {
                list->item->object.flags |= RANGE_UPDATE;
                list = list->next;
        }
        /* Clear the flags */
        while (list && !limited) {
                list->item->object.flags &= ~(RANGE_UPDATE | NONTRIVIAL_MERGE |
                                NEED_PRINT | EVIL_MERGE);
                list = list->next;
        }

        list = rev->commits;
        while (list) {
                struct commit_list *need_free = list;
                commit = list->item;

                if (commit->object.flags & RANGE_UPDATE)
                        assign_parents_range(rev, commit);

                if (commit->object.flags & NEED_PRINT ||
                        commit->object.flags & NONTRIVIAL_MERGE ||
                        rev->full_line_diff)
                        line_log_flush(rev, commit);

                r = lookup_line_range(rev, commit);
                if (r) {
                        cleanup(r);
                        r = NULL;
                        add_line_range(rev, commit, r);
                }

                r = lookup_decoration(&rev->nontrivial_merge, &commit->object);
                if (r) {
                        cleanup(r);
                        r = NULL;
                        add_decoration(&rev->nontrivial_merge, &commit->object, r);
                }

                list = list->next;
                free(need_free);
        }

        return 0;
}

static enum rewrite_result rewrite_one(struct rev_info *rev, struct commit **pp)
{
        struct diff_line_range *r = NULL;
        struct commit *p;
        while (1) {
                p = *pp;
                if (p->object.flags & RANGE_UPDATE)
                        assign_parents_range(rev, p);
                if (p->object.flags & NEED_PRINT || p->object.flags & NONTRIVIAL_MERGE)
                        return rewrite_one_ok;
                if (!p->parents)
                        return rewrite_one_noparents;

                r = lookup_line_range(rev, p);
                if (!r)
                        return rewrite_one_noparents;
                *pp = p->parents->item;
        }
}

/* The rev->commits must be sorted in topologically order */
void limit_list_line(struct rev_info *rev)
{
        struct commit_list *list = rev->commits;
        struct commit_list *commits = xmalloc(sizeof(struct commit_list));
        struct commit_list *out = commits, *prev = commits;
        struct commit *c;
        struct diff_line_range *r;

        if (list) {
                list->item->object.flags |= RANGE_UPDATE;
                list = list->next;
        }
        /* Clear the flags */
        while (list) {
                list->item->object.flags &= ~(RANGE_UPDATE | NONTRIVIAL_MERGE |
                                                NEED_PRINT | EVIL_MERGE);
                list = list->next;
        }

        list = rev->commits;
        while (list) {
                c = list->item;

                if (c->object.flags & RANGE_UPDATE)
                        assign_parents_range(rev, c);

                if (c->object.flags & NEED_PRINT || c->object.flags & NONTRIVIAL_MERGE) {
                        if (rewrite_parents(rev, c, rewrite_one))
                                die("Can't rewrite parent for commit %s",
                                        sha1_to_hex(c->object.sha1));
                        commits->item = c;
                        commits->next = xmalloc(sizeof(struct commit_list));
                        prev = commits;
                        commits = commits->next;
                } else {
                        r = lookup_line_range(rev, c);
                        if (r) {
                                cleanup(r);
                                r = NULL;
                                add_line_range(rev, c, r);
                        }
                }

                list = list->next;
        }

        prev->next = NULL;
        free(commits);

        list = rev->commits;
        while (list) {
                struct commit_list *l = list;
                list = list->next;
                free(l);
        }

        rev->commits = out;
        limited = 1;
}