Merge branch 'rs/blame-refactor'
authorJunio C Hamano <gitster@pobox.com>
Wed, 25 Jun 2014 19:23:36 +0000 (12:23 -0700)
committerJunio C Hamano <gitster@pobox.com>
Wed, 25 Jun 2014 19:23:36 +0000 (12:23 -0700)
* rs/blame-refactor:
blame: simplify prepare_lines()
blame: factor out get_next_line()

1  2 
builtin/blame.c
diff --combined builtin/blame.c
index a52a279144bec14f2b2a0795f30e0c5871f60c1b,269c64873efb27ba9aa752453f0b02f7280ffae0..662e3fec44666901de4f8feda8a51385260967e0
@@@ -1,8 -1,7 +1,8 @@@
  /*
   * Blame
   *
 - * Copyright (c) 2006, Junio C Hamano
 + * Copyright (c) 2006, 2014 by its authors
 + * See COPYING for licensing conditions
   */
  
  #include "cache.h"
@@@ -19,9 -18,7 +19,9 @@@
  #include "cache-tree.h"
  #include "string-list.h"
  #include "mailmap.h"
 +#include "mergesort.h"
  #include "parse-options.h"
 +#include "prio-queue.h"
  #include "utf8.h"
  #include "userdiff.h"
  #include "line-range.h"
@@@ -86,42 -83,11 +86,42 @@@ static unsigned blame_copy_score
   */
  struct origin {
        int refcnt;
 +      /* Record preceding blame record for this blob */
        struct origin *previous;
 +      /* origins are put in a list linked via `next' hanging off the
 +       * corresponding commit's util field in order to make finding
 +       * them fast.  The presence in this chain does not count
 +       * towards the origin's reference count.  It is tempting to
 +       * let it count as long as the commit is pending examination,
 +       * but even under circumstances where the commit will be
 +       * present multiple times in the priority queue of unexamined
 +       * commits, processing the first instance will not leave any
 +       * work requiring the origin data for the second instance.  An
 +       * interspersed commit changing that would have to be
 +       * preexisting with a different ancestry and with the same
 +       * commit date in order to wedge itself between two instances
 +       * of the same commit in the priority queue _and_ produce
 +       * blame entries relevant for it.  While we don't want to let
 +       * us get tripped up by this case, it certainly does not seem
 +       * worth optimizing for.
 +       */
 +      struct origin *next;
        struct commit *commit;
 +      /* `suspects' contains blame entries that may be attributed to
 +       * this origin's commit or to parent commits.  When a commit
 +       * is being processed, all suspects will be moved, either by
 +       * assigning them to an origin in a different commit, or by
 +       * shipping them to the scoreboard's ent list because they
 +       * cannot be attributed to a different commit.
 +       */
 +      struct blame_entry *suspects;
        mmfile_t file;
        unsigned char blob_sha1[20];
        unsigned mode;
 +      /* guilty gets set when shipping any suspects to the final
 +       * blame list instead of other commits
 +       */
 +      char guilty;
        char path[FLEX_ARRAY];
  };
  
@@@ -210,22 -176,10 +210,22 @@@ static inline struct origin *origin_inc
  static void origin_decref(struct origin *o)
  {
        if (o && --o->refcnt <= 0) {
 +              struct origin *p, *l = NULL;
                if (o->previous)
                        origin_decref(o->previous);
                free(o->file.ptr);
 -              free(o);
 +              /* Should be present exactly once in commit chain */
 +              for (p = o->commit->util; p; l = p, p = p->next) {
 +                      if (p == o) {
 +                              if (l)
 +                                      l->next = p->next;
 +                              else
 +                                      o->commit->util = p->next;
 +                              free(o);
 +                              return;
 +                      }
 +              }
 +              die("internal error in blame::origin_decref");
        }
  }
  
@@@ -239,12 -193,8 +239,12 @@@ static void drop_origin_blob(struct ori
  
  /*
   * Each group of lines is described by a blame_entry; it can be split
 - * as we pass blame to the parents.  They form a linked list in the
 - * scoreboard structure, sorted by the target line number.
 + * as we pass blame to the parents.  They are arranged in linked lists
 + * kept as `suspects' of some unprocessed origin, or entered (when the
 + * blame origin has been finalized) into the scoreboard structure.
 + * While the scoreboard structure is only sorted at the end of
 + * processing (according to final image line number), the lists
 + * attached to an origin are sorted by the target line number.
   */
  struct blame_entry {
        struct blame_entry *next;
        /* the commit that introduced this group into the final image */
        struct origin *suspect;
  
 -      /* true if the suspect is truly guilty; false while we have not
 -       * checked if the group came from one of its parents.
 -       */
 -      char guilty;
 -
 -      /* true if the entry has been scanned for copies in the current parent
 -       */
 -      char scanned;
 -
        /* the line number of the first line of this group in the
         * suspect's file; internally all line numbers are 0 based.
         */
        unsigned score;
  };
  
 +/*
 + * Any merge of blames happens on lists of blames that arrived via
 + * different parents in a single suspect.  In this case, we want to
 + * sort according to the suspect line numbers as opposed to the final
 + * image line numbers.  The function body is somewhat longish because
 + * it avoids unnecessary writes.
 + */
 +
 +static struct blame_entry *blame_merge(struct blame_entry *list1,
 +                                     struct blame_entry *list2)
 +{
 +      struct blame_entry *p1 = list1, *p2 = list2,
 +              **tail = &list1;
 +
 +      if (!p1)
 +              return p2;
 +      if (!p2)
 +              return p1;
 +
 +      if (p1->s_lno <= p2->s_lno) {
 +              do {
 +                      tail = &p1->next;
 +                      if ((p1 = *tail) == NULL) {
 +                              *tail = p2;
 +                              return list1;
 +                      }
 +              } while (p1->s_lno <= p2->s_lno);
 +      }
 +      for (;;) {
 +              *tail = p2;
 +              do {
 +                      tail = &p2->next;
 +                      if ((p2 = *tail) == NULL)  {
 +                              *tail = p1;
 +                              return list1;
 +                      }
 +              } while (p1->s_lno > p2->s_lno);
 +              *tail = p1;
 +              do {
 +                      tail = &p1->next;
 +                      if ((p1 = *tail) == NULL) {
 +                              *tail = p2;
 +                              return list1;
 +                      }
 +              } while (p1->s_lno <= p2->s_lno);
 +      }
 +}
 +
 +static void *get_next_blame(const void *p)
 +{
 +      return ((struct blame_entry *)p)->next;
 +}
 +
 +static void set_next_blame(void *p1, void *p2)
 +{
 +      ((struct blame_entry *)p1)->next = p2;
 +}
 +
 +/*
 + * Final image line numbers are all different, so we don't need a
 + * three-way comparison here.
 + */
 +
 +static int compare_blame_final(const void *p1, const void *p2)
 +{
 +      return ((struct blame_entry *)p1)->lno > ((struct blame_entry *)p2)->lno
 +              ? 1 : -1;
 +}
 +
 +static int compare_blame_suspect(const void *p1, const void *p2)
 +{
 +      const struct blame_entry *s1 = p1, *s2 = p2;
 +      /*
 +       * to allow for collating suspects, we sort according to the
 +       * respective pointer value as the primary sorting criterion.
 +       * The actual relation is pretty unimportant as long as it
 +       * establishes a total order.  Comparing as integers gives us
 +       * that.
 +       */
 +      if (s1->suspect != s2->suspect)
 +              return (intptr_t)s1->suspect > (intptr_t)s2->suspect ? 1 : -1;
 +      if (s1->s_lno == s2->s_lno)
 +              return 0;
 +      return s1->s_lno > s2->s_lno ? 1 : -1;
 +}
 +
 +static struct blame_entry *blame_sort(struct blame_entry *head,
 +                                    int (*compare_fn)(const void *, const void *))
 +{
 +      return llist_mergesort (head, get_next_blame, set_next_blame, compare_fn);
 +}
 +
 +static int compare_commits_by_reverse_commit_date(const void *a,
 +                                                const void *b,
 +                                                void *c)
 +{
 +      return -compare_commits_by_commit_date(a, b, c);
 +}
 +
  /*
   * The current state of the blame assignment.
   */
  struct scoreboard {
        /* the final commit (i.e. where we started digging from) */
        struct commit *final;
 +      /* Priority queue for commits with unassigned blame records */
 +      struct prio_queue commits;
        struct rev_info *revs;
        const char *path;
  
@@@ -410,6 -268,7 +410,6 @@@ static void coalesce(struct scoreboard 
  
        for (ent = sb->ent; ent && (next = ent->next); ent = next) {
                if (ent->suspect == next->suspect &&
 -                  ent->guilty == next->guilty &&
                    ent->s_lno + ent->num_lines == next->s_lno) {
                        ent->num_lines += next->num_lines;
                        ent->next = next->next;
                sanity_check_refcnt(sb);
  }
  
 +/*
 + * Merge the given sorted list of blames into a preexisting origin.
 + * If there were no previous blames to that commit, it is entered into
 + * the commit priority queue of the score board.
 + */
 +
 +static void queue_blames(struct scoreboard *sb, struct origin *porigin,
 +                       struct blame_entry *sorted)
 +{
 +      if (porigin->suspects)
 +              porigin->suspects = blame_merge(porigin->suspects, sorted);
 +      else {
 +              struct origin *o;
 +              for (o = porigin->commit->util; o; o = o->next) {
 +                      if (o->suspects) {
 +                              porigin->suspects = sorted;
 +                              return;
 +                      }
 +              }
 +              porigin->suspects = sorted;
 +              prio_queue_put(&sb->commits, porigin->commit);
 +      }
 +}
 +
  /*
   * Given a commit and a path in it, create a new origin structure.
   * The callers that add blame to the scoreboard should use
@@@ -460,32 -295,23 +460,32 @@@ static struct origin *make_origin(struc
        o = xcalloc(1, sizeof(*o) + strlen(path) + 1);
        o->commit = commit;
        o->refcnt = 1;
 +      o->next = commit->util;
 +      commit->util = o;
        strcpy(o->path, path);
        return o;
  }
  
  /*
   * Locate an existing origin or create a new one.
 + * This moves the origin to front position in the commit util list.
   */
  static struct origin *get_origin(struct scoreboard *sb,
                                 struct commit *commit,
                                 const char *path)
  {
 -      struct blame_entry *e;
 +      struct origin *o, *l;
  
 -      for (e = sb->ent; e; e = e->next) {
 -              if (e->suspect->commit == commit &&
 -                  !strcmp(e->suspect->path, path))
 -                      return origin_incref(e->suspect);
 +      for (o = commit->util, l = NULL; o; l = o, o = o->next) {
 +              if (!strcmp(o->path, path)) {
 +                      /* bump to front */
 +                      if (l) {
 +                              l->next = o->next;
 +                              o->next = commit->util;
 +                              commit->util = o;
 +                      }
 +                      return origin_incref(o);
 +              }
        }
        return make_origin(commit, path);
  }
@@@ -524,19 -350,41 +524,19 @@@ static struct origin *find_origin(struc
                                  struct commit *parent,
                                  struct origin *origin)
  {
 -      struct origin *porigin = NULL;
 +      struct origin *porigin;
        struct diff_options diff_opts;
        const char *paths[2];
  
 -      if (parent->util) {
 -              /*
 -               * Each commit object can cache one origin in that
 -               * commit.  This is a freestanding copy of origin and
 -               * not refcounted.
 -               */
 -              struct origin *cached = parent->util;
 -              if (!strcmp(cached->path, origin->path)) {
 +      /* First check any existing origins */
 +      for (porigin = parent->util; porigin; porigin = porigin->next)
 +              if (!strcmp(porigin->path, origin->path)) {
                        /*
                         * The same path between origin and its parent
                         * without renaming -- the most common case.
                         */
 -                      porigin = get_origin(sb, parent, cached->path);
 -
 -                      /*
 -                       * If the origin was newly created (i.e. get_origin
 -                       * would call make_origin if none is found in the
 -                       * scoreboard), it does not know the blob_sha1/mode,
 -                       * so copy it.  Otherwise porigin was in the
 -                       * scoreboard and already knows blob_sha1/mode.
 -                       */
 -                      if (porigin->refcnt == 1) {
 -                              hashcpy(porigin->blob_sha1, cached->blob_sha1);
 -                              porigin->mode = cached->mode;
 -                      }
 -                      return porigin;
 +                      return origin_incref (porigin);
                }
 -              /* otherwise it was not very useful; free it */
 -              free(parent->util);
 -              parent->util = NULL;
 -      }
  
        /* See if the origin->path is different between parent
         * and origin first.  Most of the time they are the
        }
        diff_flush(&diff_opts);
        free_pathspec(&diff_opts.pathspec);
 -      if (porigin) {
 -              /*
 -               * Create a freestanding copy that is not part of
 -               * the refcounted origin found in the scoreboard, and
 -               * cache it in the commit.
 -               */
 -              struct origin *cached;
 -
 -              cached = make_origin(porigin->commit, porigin->path);
 -              hashcpy(cached->blob_sha1, porigin->blob_sha1);
 -              cached->mode = porigin->mode;
 -              parent->util = cached;
 -      }
        return porigin;
  }
  
@@@ -648,31 -509,46 +648,31 @@@ static struct origin *find_rename(struc
  }
  
  /*
 - * Link in a new blame entry to the scoreboard.  Entries that cover the
 - * same line range have been removed from the scoreboard previously.
 + * Append a new blame entry to a given output queue.
   */
 -static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
 +static void add_blame_entry(struct blame_entry ***queue, struct blame_entry *e)
  {
 -      struct blame_entry *ent, *prev = NULL;
 -
        origin_incref(e->suspect);
  
 -      for (ent = sb->ent; ent && ent->lno < e->lno; ent = ent->next)
 -              prev = ent;
 -
 -      /* prev, if not NULL, is the last one that is below e */
 -
 -      if (prev) {
 -              e->next = prev->next;
 -              prev->next = e;
 -      }
 -      else {
 -              e->next = sb->ent;
 -              sb->ent = e;
 -      }
 +      e->next = **queue;
 +      **queue = e;
 +      *queue = &e->next;
  }
  
  /*
   * src typically is on-stack; we want to copy the information in it to
 - * a malloced blame_entry that is already on the linked list of the
 - * scoreboard.  The origin of dst loses a refcnt while the origin of src
 - * gains one.
 + * a malloced blame_entry that gets added to the given queue.  The
 + * origin of dst loses a refcnt.
   */
 -static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
 +static void dup_entry(struct blame_entry ***queue,
 +                    struct blame_entry *dst, struct blame_entry *src)
  {
 -      struct blame_entry *n;
 -
 -      n = dst->next;
        origin_incref(src->suspect);
        origin_decref(dst->suspect);
        memcpy(dst, src, sizeof(*src));
 -      dst->next = n;
 -      dst->score = 0;
 +      dst->next = **queue;
 +      **queue = dst;
 +      *queue = &dst->next;
  }
  
  static const char *nth_line(struct scoreboard *sb, long lno)
@@@ -744,11 -620,10 +744,11 @@@ static void split_overlap(struct blame_
  
  /*
   * split_overlap() divided an existing blame e into up to three parts
 - * in split.  Adjust the linked list of blames in the scoreboard to
 + * in split.  Any assigned blame is moved to queue to
   * reflect the split.
   */
 -static void split_blame(struct scoreboard *sb,
 +static void split_blame(struct blame_entry ***blamed,
 +                      struct blame_entry ***unblamed,
                        struct blame_entry *split,
                        struct blame_entry *e)
  {
  
        if (split[0].suspect && split[2].suspect) {
                /* The first part (reuse storage for the existing entry e) */
 -              dup_entry(e, &split[0]);
 +              dup_entry(unblamed, e, &split[0]);
  
                /* The last part -- me */
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
 -              add_blame_entry(sb, new_entry);
 +              add_blame_entry(unblamed, new_entry);
  
                /* ... and the middle part -- parent */
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
 -              add_blame_entry(sb, new_entry);
 +              add_blame_entry(blamed, new_entry);
        }
        else if (!split[0].suspect && !split[2].suspect)
                /*
                 * The parent covers the entire area; reuse storage for
                 * e and replace it with the parent.
                 */
 -              dup_entry(e, &split[1]);
 +              dup_entry(blamed, e, &split[1]);
        else if (split[0].suspect) {
                /* me and then parent */
 -              dup_entry(e, &split[0]);
 +              dup_entry(unblamed, e, &split[0]);
  
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
 -              add_blame_entry(sb, new_entry);
 +              add_blame_entry(blamed, new_entry);
        }
        else {
                /* parent and then me */
 -              dup_entry(e, &split[1]);
 +              dup_entry(blamed, e, &split[1]);
  
                new_entry = xmalloc(sizeof(*new_entry));
                memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
 -              add_blame_entry(sb, new_entry);
 -      }
 -
 -      if (DEBUG) { /* sanity */
 -              struct blame_entry *ent;
 -              int lno = sb->ent->lno, corrupt = 0;
 -
 -              for (ent = sb->ent; ent; ent = ent->next) {
 -                      if (lno != ent->lno)
 -                              corrupt = 1;
 -                      if (ent->s_lno < 0)
 -                              corrupt = 1;
 -                      lno += ent->num_lines;
 -              }
 -              if (corrupt) {
 -                      lno = sb->ent->lno;
 -                      for (ent = sb->ent; ent; ent = ent->next) {
 -                              printf("L %8d l %8d n %8d\n",
 -                                     lno, ent->lno, ent->num_lines);
 -                              lno = ent->lno + ent->num_lines;
 -                      }
 -                      die("oops");
 -              }
 +              add_blame_entry(unblamed, new_entry);
        }
  }
  
@@@ -805,146 -702,74 +805,146 @@@ static void decref_split(struct blame_e
  }
  
  /*
 - * Helper for blame_chunk().  blame_entry e is known to overlap with
 - * the patch hunk; split it and pass blame to the parent.
 + * reverse_blame reverses the list given in head, appending tail.
 + * That allows us to build lists in reverse order, then reverse them
 + * afterwards.  This can be faster than building the list in proper
 + * order right away.  The reason is that building in proper order
 + * requires writing a link in the _previous_ element, while building
 + * in reverse order just requires placing the list head into the
 + * _current_ element.
   */
 -static void blame_overlap(struct scoreboard *sb, struct blame_entry *e,
 -                        int tlno, int plno, int same,
 -                        struct origin *parent)
 -{
 -      struct blame_entry split[3];
 -
 -      split_overlap(split, e, tlno, plno, same, parent);
 -      if (split[1].suspect)
 -              split_blame(sb, split, e);
 -      decref_split(split);
 -}
  
 -/*
 - * Find the line number of the last line the target is suspected for.
 - */
 -static int find_last_in_target(struct scoreboard *sb, struct origin *target)
 +static struct blame_entry *reverse_blame(struct blame_entry *head,
 +                                       struct blame_entry *tail)
  {
 -      struct blame_entry *e;
 -      int last_in_target = -1;
 -
 -      for (e = sb->ent; e; e = e->next) {
 -              if (e->guilty || e->suspect != target)
 -                      continue;
 -              if (last_in_target < e->s_lno + e->num_lines)
 -                      last_in_target = e->s_lno + e->num_lines;
 +      while (head) {
 +              struct blame_entry *next = head->next;
 +              head->next = tail;
 +              tail = head;
 +              head = next;
        }
 -      return last_in_target;
 +      return tail;
  }
  
  /*
   * Process one hunk from the patch between the current suspect for
 - * blame_entry e and its parent.  Find and split the overlap, and
 - * pass blame to the overlapping part to the parent.
 + * blame_entry e and its parent.  This first blames any unfinished
 + * entries before the chunk (which is where target and parent start
 + * differing) on the parent, and then splits blame entries at the
 + * start and at the end of the difference region.  Since use of -M and
 + * -C options may lead to overlapping/duplicate source line number
 + * ranges, all we can rely on from sorting/merging is the order of the
 + * first suspect line number.
   */
 -static void blame_chunk(struct scoreboard *sb,
 -                      int tlno, int plno, int same,
 -                      struct origin *target, struct origin *parent)
 +static void blame_chunk(struct blame_entry ***dstq, struct blame_entry ***srcq,
 +                      int tlno, int offset, int same,
 +                      struct origin *parent)
  {
 -      struct blame_entry *e;
 +      struct blame_entry *e = **srcq;
 +      struct blame_entry *samep = NULL, *diffp = NULL;
  
 -      for (e = sb->ent; e; e = e->next) {
 -              if (e->guilty || e->suspect != target)
 -                      continue;
 -              if (same <= e->s_lno)
 -                      continue;
 -              if (tlno < e->s_lno + e->num_lines)
 -                      blame_overlap(sb, e, tlno, plno, same, parent);
 +      while (e && e->s_lno < tlno) {
 +              struct blame_entry *next = e->next;
 +              /*
 +               * current record starts before differing portion.  If
 +               * it reaches into it, we need to split it up and
 +               * examine the second part separately.
 +               */
 +              if (e->s_lno + e->num_lines > tlno) {
 +                      /* Move second half to a new record */
 +                      int len = tlno - e->s_lno;
 +                      struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
 +                      n->suspect = e->suspect;
 +                      n->lno = e->lno + len;
 +                      n->s_lno = e->s_lno + len;
 +                      n->num_lines = e->num_lines - len;
 +                      e->num_lines = len;
 +                      e->score = 0;
 +                      /* Push new record to diffp */
 +                      n->next = diffp;
 +                      diffp = n;
 +              } else
 +                      origin_decref(e->suspect);
 +              /* Pass blame for everything before the differing
 +               * chunk to the parent */
 +              e->suspect = origin_incref(parent);
 +              e->s_lno += offset;
 +              e->next = samep;
 +              samep = e;
 +              e = next;
 +      }
 +      /*
 +       * As we don't know how much of a common stretch after this
 +       * diff will occur, the currently blamed parts are all that we
 +       * can assign to the parent for now.
 +       */
 +
 +      if (samep) {
 +              **dstq = reverse_blame(samep, **dstq);
 +              *dstq = &samep->next;
 +      }
 +      /*
 +       * Prepend the split off portions: everything after e starts
 +       * after the blameable portion.
 +       */
 +      e = reverse_blame(diffp, e);
 +
 +      /*
 +       * Now retain records on the target while parts are different
 +       * from the parent.
 +       */
 +      samep = NULL;
 +      diffp = NULL;
 +      while (e && e->s_lno < same) {
 +              struct blame_entry *next = e->next;
 +
 +              /*
 +               * If current record extends into sameness, need to split.
 +               */
 +              if (e->s_lno + e->num_lines > same) {
 +                      /*
 +                       * Move second half to a new record to be
 +                       * processed by later chunks
 +                       */
 +                      int len = same - e->s_lno;
 +                      struct blame_entry *n = xcalloc(1, sizeof (struct blame_entry));
 +                      n->suspect = origin_incref(e->suspect);
 +                      n->lno = e->lno + len;
 +                      n->s_lno = e->s_lno + len;
 +                      n->num_lines = e->num_lines - len;
 +                      e->num_lines = len;
 +                      e->score = 0;
 +                      /* Push new record to samep */
 +                      n->next = samep;
 +                      samep = n;
 +              }
 +              e->next = diffp;
 +              diffp = e;
 +              e = next;
        }
 +      **srcq = reverse_blame(diffp, reverse_blame(samep, e));
 +      /* Move across elements that are in the unblamable portion */
 +      if (diffp)
 +              *srcq = &diffp->next;
  }
  
  struct blame_chunk_cb_data {
 -      struct scoreboard *sb;
 -      struct origin *target;
        struct origin *parent;
 -      long plno;
 -      long tlno;
 +      long offset;
 +      struct blame_entry **dstq;
 +      struct blame_entry **srcq;
  };
  
 +/* diff chunks are from parent to target */
  static int blame_chunk_cb(long start_a, long count_a,
                          long start_b, long count_b, void *data)
  {
        struct blame_chunk_cb_data *d = data;
 -      blame_chunk(d->sb, d->tlno, d->plno, start_b, d->target, d->parent);
 -      d->plno = start_a + count_a;
 -      d->tlno = start_b + count_b;
 +      if (start_a - start_b != d->offset)
 +              die("internal error in blame::blame_chunk_cb");
 +      blame_chunk(&d->dstq, &d->srcq, start_b, start_a - start_b,
 +                  start_b + count_b, d->parent);
 +      d->offset = start_a + count_a - (start_b + count_b);
        return 0;
  }
  
   * for the lines it is suspected to its parent.  Run diff to find
   * which lines came from parent and pass blame for them.
   */
 -static int pass_blame_to_parent(struct scoreboard *sb,
 -                              struct origin *target,
 -                              struct origin *parent)
 +static void pass_blame_to_parent(struct scoreboard *sb,
 +                               struct origin *target,
 +                               struct origin *parent)
  {
 -      int last_in_target;
        mmfile_t file_p, file_o;
        struct blame_chunk_cb_data d;
 +      struct blame_entry *newdest = NULL;
  
 -      memset(&d, 0, sizeof(d));
 -      d.sb = sb; d.target = target; d.parent = parent;
 -      last_in_target = find_last_in_target(sb, target);
 -      if (last_in_target < 0)
 -              return 1; /* nothing remains for this target */
 +      if (!target->suspects)
 +              return; /* nothing remains for this target */
 +
 +      d.parent = parent;
 +      d.offset = 0;
 +      d.dstq = &newdest; d.srcq = &target->suspects;
  
        fill_origin_blob(&sb->revs->diffopt, parent, &file_p);
        fill_origin_blob(&sb->revs->diffopt, target, &file_o);
        num_get_patch++;
  
        diff_hunks(&file_p, &file_o, 0, blame_chunk_cb, &d);
 -      /* The rest (i.e. anything after tlno) are the same as the parent */
 -      blame_chunk(sb, d.tlno, d.plno, last_in_target, target, parent);
 +      /* The rest are the same as the parent */
 +      blame_chunk(&d.dstq, &d.srcq, INT_MAX, d.offset, INT_MAX, parent);
 +      *d.dstq = NULL;
 +      queue_blames(sb, parent, newdest);
  
 -      return 0;
 +      return;
  }
  
  /*
@@@ -1123,80 -945,43 +1123,80 @@@ static void find_copy_in_blob(struct sc
        handle_split(sb, ent, d.tlno, d.plno, ent->num_lines, parent, split);
  }
  
 +/* Move all blame entries from list *source that have a score smaller
 + * than score_min to the front of list *small.
 + * Returns a pointer to the link pointing to the old head of the small list.
 + */
 +
 +static struct blame_entry **filter_small(struct scoreboard *sb,
 +                                       struct blame_entry **small,
 +                                       struct blame_entry **source,
 +                                       unsigned score_min)
 +{
 +      struct blame_entry *p = *source;
 +      struct blame_entry *oldsmall = *small;
 +      while (p) {
 +              if (ent_score(sb, p) <= score_min) {
 +                      *small = p;
 +                      small = &p->next;
 +                      p = *small;
 +              } else {
 +                      *source = p;
 +                      source = &p->next;
 +                      p = *source;
 +              }
 +      }
 +      *small = oldsmall;
 +      *source = NULL;
 +      return small;
 +}
 +
  /*
   * See if lines currently target is suspected for can be attributed to
   * parent.
   */
 -static int find_move_in_parent(struct scoreboard *sb,
 -                             struct origin *target,
 -                             struct origin *parent)
 +static void find_move_in_parent(struct scoreboard *sb,
 +                              struct blame_entry ***blamed,
 +                              struct blame_entry **toosmall,
 +                              struct origin *target,
 +                              struct origin *parent)
  {
 -      int last_in_target, made_progress;
        struct blame_entry *e, split[3];
 +      struct blame_entry *unblamed = target->suspects;
 +      struct blame_entry *leftover = NULL;
        mmfile_t file_p;
  
 -      last_in_target = find_last_in_target(sb, target);
 -      if (last_in_target < 0)
 -              return 1; /* nothing remains for this target */
 +      if (!unblamed)
 +              return; /* nothing remains for this target */
  
        fill_origin_blob(&sb->revs->diffopt, parent, &file_p);
        if (!file_p.ptr)
 -              return 0;
 +              return;
  
 -      made_progress = 1;
 -      while (made_progress) {
 -              made_progress = 0;
 -              for (e = sb->ent; e; e = e->next) {
 -                      if (e->guilty || e->suspect != target ||
 -                          ent_score(sb, e) < blame_move_score)
 -                              continue;
 +      /* At each iteration, unblamed has a NULL-terminated list of
 +       * entries that have not yet been tested for blame.  leftover
 +       * contains the reversed list of entries that have been tested
 +       * without being assignable to the parent.
 +       */
 +      do {
 +              struct blame_entry **unblamedtail = &unblamed;
 +              struct blame_entry *next;
 +              for (e = unblamed; e; e = next) {
 +                      next = e->next;
                        find_copy_in_blob(sb, e, parent, split, &file_p);
                        if (split[1].suspect &&
                            blame_move_score < ent_score(sb, &split[1])) {
 -                              split_blame(sb, split, e);
 -                              made_progress = 1;
 +                              split_blame(blamed, &unblamedtail, split, e);
 +                      } else {
 +                              e->next = leftover;
 +                              leftover = e;
                        }
                        decref_split(split);
                }
 -      }
 -      return 0;
 +              *unblamedtail = NULL;
 +              toosmall = filter_small(sb, toosmall, &unblamed, blame_move_score);
 +      } while (unblamed);
 +      target->suspects = reverse_blame(leftover, NULL);
  }
  
  struct blame_list {
   * Count the number of entries the target is suspected for,
   * and prepare a list of entry and the best split.
   */
 -static struct blame_list *setup_blame_list(struct scoreboard *sb,
 -                                         struct origin *target,
 -                                         int min_score,
 +static struct blame_list *setup_blame_list(struct blame_entry *unblamed,
                                           int *num_ents_p)
  {
        struct blame_entry *e;
        int num_ents, i;
        struct blame_list *blame_list = NULL;
  
 -      for (e = sb->ent, num_ents = 0; e; e = e->next)
 -              if (!e->scanned && !e->guilty &&
 -                  e->suspect == target &&
 -                  min_score < ent_score(sb, e))
 -                      num_ents++;
 +      for (e = unblamed, num_ents = 0; e; e = e->next)
 +              num_ents++;
        if (num_ents) {
                blame_list = xcalloc(num_ents, sizeof(struct blame_list));
 -              for (e = sb->ent, i = 0; e; e = e->next)
 -                      if (!e->scanned && !e->guilty &&
 -                          e->suspect == target &&
 -                          min_score < ent_score(sb, e))
 -                              blame_list[i++].ent = e;
 +              for (e = unblamed, i = 0; e; e = e->next)
 +                      blame_list[i++].ent = e;
        }
        *num_ents_p = num_ents;
        return blame_list;
  }
  
 -/*
 - * Reset the scanned status on all entries.
 - */
 -static void reset_scanned_flag(struct scoreboard *sb)
 -{
 -      struct blame_entry *e;
 -      for (e = sb->ent; e; e = e->next)
 -              e->scanned = 0;
 -}
 -
  /*
   * For lines target is suspected for, see if we can find code movement
   * across file boundary from the parent commit.  porigin is the path
   * in the parent we already tried.
   */
 -static int find_copy_in_parent(struct scoreboard *sb,
 -                             struct origin *target,
 -                             struct commit *parent,
 -                             struct origin *porigin,
 -                             int opt)
 +static void find_copy_in_parent(struct scoreboard *sb,
 +                              struct blame_entry ***blamed,
 +                              struct blame_entry **toosmall,
 +                              struct origin *target,
 +                              struct commit *parent,
 +                              struct origin *porigin,
 +                              int opt)
  {
        struct diff_options diff_opts;
        int i, j;
 -      int retval;
        struct blame_list *blame_list;
        int num_ents;
 +      struct blame_entry *unblamed = target->suspects;
 +      struct blame_entry *leftover = NULL;
  
 -      blame_list = setup_blame_list(sb, target, blame_copy_score, &num_ents);
 -      if (!blame_list)
 -              return 1; /* nothing remains for this target */
 +      if (!unblamed)
 +              return; /* nothing remains for this target */
  
        diff_setup(&diff_opts);
        DIFF_OPT_SET(&diff_opts, RECURSIVE);
        if (!DIFF_OPT_TST(&diff_opts, FIND_COPIES_HARDER))
                diffcore_std(&diff_opts);
  
 -      retval = 0;
 -      while (1) {
 -              int made_progress = 0;
 +      do {
 +              struct blame_entry **unblamedtail = &unblamed;
 +              blame_list = setup_blame_list(unblamed, &num_ents);
  
                for (i = 0; i < diff_queued_diff.nr; i++) {
                        struct diff_filepair *p = diff_queued_diff.queue[i];
                        struct blame_entry *split = blame_list[j].split;
                        if (split[1].suspect &&
                            blame_copy_score < ent_score(sb, &split[1])) {
 -                              split_blame(sb, split, blame_list[j].ent);
 -                              made_progress = 1;
 +                              split_blame(blamed, &unblamedtail, split,
 +                                          blame_list[j].ent);
 +                      } else {
 +                              blame_list[j].ent->next = leftover;
 +                              leftover = blame_list[j].ent;
                        }
 -                      else
 -                              blame_list[j].ent->scanned = 1;
                        decref_split(split);
                }
                free(blame_list);
 -
 -              if (!made_progress)
 -                      break;
 -              blame_list = setup_blame_list(sb, target, blame_copy_score, &num_ents);
 -              if (!blame_list) {
 -                      retval = 1;
 -                      break;
 -              }
 -      }
 -      reset_scanned_flag(sb);
 +              *unblamedtail = NULL;
 +              toosmall = filter_small(sb, toosmall, &unblamed, blame_copy_score);
 +      } while (unblamed);
 +      target->suspects = reverse_blame(leftover, NULL);
        diff_flush(&diff_opts);
        free_pathspec(&diff_opts.pathspec);
 -      return retval;
  }
  
  /*
  static void pass_whole_blame(struct scoreboard *sb,
                             struct origin *origin, struct origin *porigin)
  {
 -      struct blame_entry *e;
 +      struct blame_entry *e, *suspects;
  
        if (!porigin->file.ptr && origin->file.ptr) {
                /* Steal its file */
                porigin->file = origin->file;
                origin->file.ptr = NULL;
        }
 -      for (e = sb->ent; e; e = e->next) {
 -              if (e->suspect != origin)
 -                      continue;
 +      suspects = origin->suspects;
 +      origin->suspects = NULL;
 +      for (e = suspects; e; e = e->next) {
                origin_incref(porigin);
                origin_decref(e->suspect);
                e->suspect = porigin;
        }
 +      queue_blames(sb, porigin, suspects);
  }
  
  /*
@@@ -1378,27 -1184,6 +1378,27 @@@ static int num_scapegoats(struct rev_in
        return cnt;
  }
  
 +/* Distribute collected unsorted blames to the respected sorted lists
 + * in the various origins.
 + */
 +static void distribute_blame(struct scoreboard *sb, struct blame_entry *blamed)
 +{
 +      blamed = blame_sort(blamed, compare_blame_suspect);
 +      while (blamed)
 +      {
 +              struct origin *porigin = blamed->suspect;
 +              struct blame_entry *suspects = NULL;
 +              do {
 +                      struct blame_entry *next = blamed->next;
 +                      blamed->next = suspects;
 +                      suspects = blamed;
 +                      blamed = next;
 +              } while (blamed && blamed->suspect == porigin);
 +              suspects = reverse_blame(suspects, NULL);
 +              queue_blames(sb, porigin, suspects);
 +      }
 +}
 +
  #define MAXSG 16
  
  static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
        struct commit_list *sg;
        struct origin *sg_buf[MAXSG];
        struct origin *porigin, **sg_origin = sg_buf;
 +      struct blame_entry *toosmall = NULL;
 +      struct blame_entry *blames, **blametail = &blames;
  
        num_sg = num_scapegoats(revs, commit);
        if (!num_sg)
                        origin_incref(porigin);
                        origin->previous = porigin;
                }
 -              if (pass_blame_to_parent(sb, origin, porigin))
 +              pass_blame_to_parent(sb, origin, porigin);
 +              if (!origin->suspects)
                        goto finish;
        }
  
        /*
         * Optionally find moves in parents' files.
         */
 -      if (opt & PICKAXE_BLAME_MOVE)
 -              for (i = 0, sg = first_scapegoat(revs, commit);
 -                   i < num_sg && sg;
 -                   sg = sg->next, i++) {
 -                      struct origin *porigin = sg_origin[i];
 -                      if (!porigin)
 -                              continue;
 -                      if (find_move_in_parent(sb, origin, porigin))
 -                              goto finish;
 +      if (opt & PICKAXE_BLAME_MOVE) {
 +              filter_small(sb, &toosmall, &origin->suspects, blame_move_score);
 +              if (origin->suspects) {
 +                      for (i = 0, sg = first_scapegoat(revs, commit);
 +                           i < num_sg && sg;
 +                           sg = sg->next, i++) {
 +                              struct origin *porigin = sg_origin[i];
 +                              if (!porigin)
 +                                      continue;
 +                              find_move_in_parent(sb, &blametail, &toosmall, origin, porigin);
 +                              if (!origin->suspects)
 +                                      break;
 +                      }
                }
 +      }
  
        /*
         * Optionally find copies from parents' files.
         */
 -      if (opt & PICKAXE_BLAME_COPY)
 +      if (opt & PICKAXE_BLAME_COPY) {
 +              if (blame_copy_score > blame_move_score)
 +                      filter_small(sb, &toosmall, &origin->suspects, blame_copy_score);
 +              else if (blame_copy_score < blame_move_score) {
 +                      origin->suspects = blame_merge(origin->suspects, toosmall);
 +                      toosmall = NULL;
 +                      filter_small(sb, &toosmall, &origin->suspects, blame_copy_score);
 +              }
 +              if (!origin->suspects)
 +                      goto finish;
 +
                for (i = 0, sg = first_scapegoat(revs, commit);
                     i < num_sg && sg;
                     sg = sg->next, i++) {
                        struct origin *porigin = sg_origin[i];
 -                      if (find_copy_in_parent(sb, origin, sg->item,
 -                                              porigin, opt))
 +                      find_copy_in_parent(sb, &blametail, &toosmall,
 +                                          origin, sg->item, porigin, opt);
 +                      if (!origin->suspects)
                                goto finish;
                }
 +      }
  
 - finish:
 +finish:
 +      *blametail = NULL;
 +      distribute_blame(sb, blames);
 +      /*
 +       * prepend toosmall to origin->suspects
 +       *
 +       * There is no point in sorting: this ends up on a big
 +       * unsorted list in the caller anyway.
 +       */
 +      if (toosmall) {
 +              struct blame_entry **tail = &toosmall;
 +              while (*tail)
 +                      tail = &(*tail)->next;
 +              *tail = origin->suspects;
 +              origin->suspects = toosmall;
 +      }
        for (i = 0; i < num_sg; i++) {
                if (sg_origin[i]) {
                        drop_origin_blob(sg_origin[i]);
@@@ -1731,11 -1481,14 +1731,11 @@@ static int emit_one_suspect_detail(stru
  }
  
  /*
 - * The blame_entry is found to be guilty for the range.  Mark it
 - * as such, and show it in incremental output.
 + * The blame_entry is found to be guilty for the range.
 + * Show it in incremental output.
   */
  static void found_guilty_entry(struct blame_entry *ent)
  {
 -      if (ent->guilty)
 -              return;
 -      ent->guilty = 1;
        if (incremental) {
                struct origin *suspect = ent->suspect;
  
  }
  
  /*
 - * The main loop -- while the scoreboard has lines whose true origin
 - * is still unknown, pick one blame_entry, and allow its current
 - * suspect to pass blames to its parents.
 - */
 + * The main loop -- while we have blobs with lines whose true origin
 + * is still unknown, pick one blob, and allow its lines to pass blames
 + * to its parents. */
  static void assign_blame(struct scoreboard *sb, int opt)
  {
        struct rev_info *revs = sb->revs;
 +      struct commit *commit = prio_queue_get(&sb->commits);
  
 -      while (1) {
 +      while (commit) {
                struct blame_entry *ent;
 -              struct commit *commit;
 -              struct origin *suspect = NULL;
 +              struct origin *suspect = commit->util;
  
                /* find one suspect to break down */
 -              for (ent = sb->ent; !suspect && ent; ent = ent->next)
 -                      if (!ent->guilty)
 -                              suspect = ent->suspect;
 -              if (!suspect)
 -                      return; /* all done */
 +              while (suspect && !suspect->suspects)
 +                      suspect = suspect->next;
 +
 +              if (!suspect) {
 +                      commit = prio_queue_get(&sb->commits);
 +                      continue;
 +              }
 +
 +              assert(commit == suspect->commit);
  
                /*
                 * We will use this suspect later in the loop,
                 * so hold onto it in the meantime.
                 */
                origin_incref(suspect);
 -              commit = suspect->commit;
                parse_commit(commit);
                if (reverse ||
                    (!(commit->object.flags & UNINTERESTING) &&
                        commit->object.flags |= UNINTERESTING;
  
                /* Take responsibility for the remaining entries */
 -              for (ent = sb->ent; ent; ent = ent->next)
 -                      if (ent->suspect == suspect)
 +              ent = suspect->suspects;
 +              if (ent) {
 +                      suspect->guilty = 1;
 +                      for (;;) {
 +                              struct blame_entry *next = ent->next;
                                found_guilty_entry(ent);
 +                              if (next) {
 +                                      ent = next;
 +                                      continue;
 +                              }
 +                              ent->next = sb->ent;
 +                              sb->ent = suspect->suspects;
 +                              suspect->suspects = NULL;
 +                              break;
 +                      }
 +              }
                origin_decref(suspect);
  
                if (DEBUG) /* sanity */
  static const char *format_time(unsigned long time, const char *tz_str,
                               int show_raw_time)
  {
 -      static char time_buf[128];
 +      static struct strbuf time_buf = STRBUF_INIT;
  
 +      strbuf_reset(&time_buf);
        if (show_raw_time) {
 -              snprintf(time_buf, sizeof(time_buf), "%lu %s", time, tz_str);
 +              strbuf_addf(&time_buf, "%lu %s", time, tz_str);
        }
        else {
                const char *time_str;
 -              int time_len;
 +              size_t time_width;
                int tz;
                tz = atoi(tz_str);
                time_str = show_date(time, tz, blame_date_mode);
 -              time_len = strlen(time_str);
 -              memcpy(time_buf, time_str, time_len);
 -              memset(time_buf + time_len, ' ', blame_date_width - time_len);
 +              strbuf_addstr(&time_buf, time_str);
 +              /*
 +               * Add space paddings to time_buf to display a fixed width
 +               * string, and use time_width for display width calibration.
 +               */
 +              for (time_width = utf8_strwidth(time_str);
 +                   time_width < blame_date_width;
 +                   time_width++)
 +                      strbuf_addch(&time_buf, ' ');
        }
 -      return time_buf;
 +      return time_buf.buf;
  }
  
  #define OUTPUT_ANNOTATE_COMPAT        001
@@@ -1871,8 -1602,9 +1871,8 @@@ static void emit_porcelain(struct score
        char hex[41];
  
        strcpy(hex, sha1_to_hex(suspect->commit->object.sha1));
 -      printf("%s%c%d %d %d\n",
 +      printf("%s %d %d %d\n",
               hex,
 -             ent->guilty ? ' ' : '*', /* purely for debugging */
               ent->s_lno + 1,
               ent->lno + 1,
               ent->num_lines);
@@@ -1985,16 -1717,17 +1985,16 @@@ static void output(struct scoreboard *s
  
        if (option & OUTPUT_PORCELAIN) {
                for (ent = sb->ent; ent; ent = ent->next) {
 -                      struct blame_entry *oth;
 -                      struct origin *suspect = ent->suspect;
 -                      struct commit *commit = suspect->commit;
 +                      int count = 0;
 +                      struct origin *suspect;
 +                      struct commit *commit = ent->suspect->commit;
                        if (commit->object.flags & MORE_THAN_ONE_PATH)
                                continue;
 -                      for (oth = ent->next; oth; oth = oth->next) {
 -                              if ((oth->suspect->commit != commit) ||
 -                                  !strcmp(oth->suspect->path, suspect->path))
 -                                      continue;
 -                              commit->object.flags |= MORE_THAN_ONE_PATH;
 -                              break;
 +                      for (suspect = commit->util; suspect; suspect = suspect->next) {
 +                              if (suspect->guilty && count++) {
 +                                      commit->object.flags |= MORE_THAN_ONE_PATH;
 +                                      break;
 +                              }
                        }
                }
        }
        }
  }
  
+ static const char *get_next_line(const char *start, const char *end)
+ {
+       const char *nl = memchr(start, '\n', end - start);
+       return nl ? nl + 1 : end;
+ }
  /*
   * To allow quick access to the contents of nth line in the
   * final image, prepare an index in the scoreboard.
@@@ -2019,39 -1758,19 +2025,19 @@@ static int prepare_lines(struct scorebo
        const char *end = buf + len;
        const char *p;
        int *lineno;
-       int num = 0, incomplete = 0;
-       for (p = buf;;) {
-               p = memchr(p, '\n', end - p);
-               if (p) {
-                       p++;
-                       num++;
-                       continue;
-               }
-               break;
-       }
+       int num = 0;
  
-       if (len && end[-1] != '\n')
-               incomplete++; /* incomplete line at the end */
+       for (p = buf; p < end; p = get_next_line(p, end))
+               num++;
  
-       sb->lineno = xmalloc(sizeof(*sb->lineno) * (num + incomplete + 1));
-       lineno = sb->lineno;
+       sb->lineno = lineno = xmalloc(sizeof(*sb->lineno) * (num + 1));
  
-       *lineno++ = 0;
-       for (p = buf;;) {
-               p = memchr(p, '\n', end - p);
-               if (p) {
-                       p++;
-                       *lineno++ = p - buf;
-                       continue;
-               }
-               break;
-       }
+       for (p = buf; p < end; p = get_next_line(p, end))
+               *lineno++ = p - buf;
  
-       if (incomplete)
-               *lineno++ = len;
+       *lineno = len;
  
-       sb->num_lines = num + incomplete;
+       sb->num_lines = num;
        return sb->num_lines;
  }
  
@@@ -2355,9 -2074,11 +2341,9 @@@ static struct commit *fake_working_tree
                if (strbuf_read(&buf, 0, 0) < 0)
                        die_errno("failed to read from stdin");
        }
 -      convert_to_git(path, buf.buf, buf.len, &buf, 0);
        origin->file.ptr = buf.buf;
        origin->file.size = buf.len;
        pretend_sha1_file(buf.buf, buf.len, OBJ_BLOB, origin->blob_sha1);
 -      commit->util = origin;
  
        /*
         * Read the current index, replace the path entry with
@@@ -2596,14 -2317,7 +2582,14 @@@ parse_done
                blame_date_width = sizeof("2006-10-19");
                break;
        case DATE_RELATIVE:
 -              /* "normal" is used as the fallback for "relative" */
 +              /* TRANSLATORS: This string is used to tell us the maximum
 +                 display width for a relative timestamp in "git blame"
 +                 output.  For C locale, "4 years, 11 months ago", which
 +                 takes 22 places, is the longest among various forms of
 +                 relative timestamps, but your language may need more or
 +                 fewer display columns. */
 +              blame_date_width = utf8_strwidth(_("4 years, 11 months ago")) + 1; /* add the null */
 +              break;
        case DATE_LOCAL:
        case DATE_NORMAL:
                blame_date_width = sizeof("Thu Oct 19 16:00:04 2006 -0700");
        memset(&sb, 0, sizeof(sb));
  
        sb.revs = &revs;
 -      if (!reverse)
 +      if (!reverse) {
                final_commit_name = prepare_final(&sb);
 +              sb.commits.compare = compare_commits_by_commit_date;
 +      }
        else if (contents_from)
                die("--contents and --children do not blend well.");
 -      else
 +      else {
                final_commit_name = prepare_initial(&sb);
 +              sb.commits.compare = compare_commits_by_reverse_commit_date;
 +      }
  
        if (!sb.final) {
                /*
                ent->next = next;
                origin_incref(o);
        }
 +
 +      o->suspects = ent;
 +      prio_queue_put(&sb.commits, o->commit);
 +
        origin_decref(o);
  
        range_set_release(&ranges);
        string_list_clear(&range_list, 0);
  
 -      sb.ent = ent;
 +      sb.ent = NULL;
        sb.path = path;
  
        read_mailmap(&mailmap, NULL);
        if (incremental)
                return 0;
  
 +      sb.ent = blame_sort(sb.ent, compare_blame_final);
 +
        coalesce(&sb);
  
        if (!(output_option & OUTPUT_PORCELAIN))