Merge branch 'dk/blame-reorg'
authorJunio C Hamano <gitster@pobox.com>
Fri, 6 Jun 2014 18:24:44 +0000 (11:24 -0700)
committerJunio C Hamano <gitster@pobox.com>
Fri, 6 Jun 2014 18:24:44 +0000 (11:24 -0700)
"git blame" has been optimized greatly by reorganising the data
structure that is used to keep track of the work to be done, thanks
to David Karstrup <dak@gnu.org>.

* dk/blame-reorg:
blame: large-scale performance rewrite

1  2 
builtin/blame.c
diff --combined builtin/blame.c
index 128fc64d64f46af010ffcc1cf83b98705c60dabc,224f0ff07716a1796ce42440b93bdfac709370ae..3aa17933035604d5abc0385ea724e3710ce99235
@@@ -1,7 -1,8 +1,8 @@@
  /*
   * Blame
   *
-  * Copyright (c) 2006, Junio C Hamano
+  * Copyright (c) 2006, 2014 by its authors
+  * See COPYING for licensing conditions
   */
  
  #include "cache.h"
@@@ -18,7 -19,9 +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"
@@@ -83,11 -86,42 +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];
  };
  
@@@ -176,10 -210,22 +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");
        }
  }
  
@@@ -193,8 -239,12 +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;
  
@@@ -268,7 -410,6 +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
@@@ -295,23 -460,32 +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);
  }
@@@ -350,41 -524,19 +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;
  }
  
@@@ -509,46 -648,31 +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)
@@@ -620,10 -744,11 +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);
        }
  }
  
@@@ -702,74 -805,146 +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;
  }
  
  /*
@@@ -945,43 -1123,80 +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);
  }
  
  /*
@@@ -1184,6 -1378,27 +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]);
@@@ -1481,14 -1731,11 +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
@@@ -1609,9 -1864,8 +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);
@@@ -1724,17 -1978,16 +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;
+                               }
                        }
                }
        }
@@@ -2099,7 -2352,6 +2359,6 @@@ static struct commit *fake_working_tree
        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
@@@ -2338,14 -2590,7 +2597,14 @@@ 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))