cvsserver: Introduce new state variable 'method'
[gitweb.git] / builtin-blame.c
index 9bf6ec951fb5d7535441a8db5b73d20f509ed982..60ec5354f11c61c49829d41e8c07d22573f16bc7 100644 (file)
 #include "diff.h"
 #include "diffcore.h"
 #include "revision.h"
+#include "quote.h"
 #include "xdiff-interface.h"
+#include "cache-tree.h"
 
 static char blame_usage[] =
-"git-blame [-c] [-l] [-t] [-f] [-n] [-p] [-L n,m] [-S <revs-file>] [-M] [-C] [-C] [commit] [--] file\n"
+"git-blame [-c] [-l] [-t] [-f] [-n] [-p] [-L n,m] [-S <revs-file>] [-M] [-C] [-C] [--contents <filename>] [--incremental] [commit] [--] file\n"
 "  -c, --compatibility Use the same output mode as git-annotate (Default: off)\n"
+"  -b                  Show blank SHA-1 for boundary commits (Default: off)\n"
 "  -l, --long          Show long commit SHA1 (Default: off)\n"
+"  --root              Do not treat root commits as boundaries (Default: off)\n"
 "  -t, --time          Show raw timestamp (Default: off)\n"
 "  -f, --show-name     Show original filename (Default: auto)\n"
 "  -n, --show-number   Show original linenumber (Default: off)\n"
 "  -p, --porcelain     Show in a format designed for machine consumption\n"
 "  -L n,m              Process only line range n,m, counting from 1\n"
 "  -M, -C              Find line movements within and across files\n"
+"  --incremental       Show blame entries as we find them, incrementally\n"
+"  --contents file     Use <file>'s contents as the final image\n"
 "  -S revs-file        Use revisions from revs-file instead of calling git-rev-list\n";
 
 static int longest_file;
@@ -32,6 +38,10 @@ static int longest_author;
 static int max_orig_digits;
 static int max_digits;
 static int max_score_digits;
+static int show_root;
+static int blank_boundary;
+static int incremental;
+static int cmd_is_annotate;
 
 #ifndef DEBUG
 #define DEBUG 0
@@ -70,12 +80,16 @@ struct origin {
        char path[FLEX_ARRAY];
 };
 
+/*
+ * Given an origin, prepare mmfile_t structure to be used by the
+ * diff machinery
+ */
 static char *fill_origin_blob(struct origin *o, mmfile_t *file)
 {
        if (!o->file.ptr) {
-               char type[10];
+               enum object_type type;
                num_read_blob++;
-               file->ptr = read_sha1_file(o->blob_sha1, type,
+               file->ptr = read_sha1_file(o->blob_sha1, &type,
                                           (unsigned long *)(&(file->size)));
                o->file = *file;
        }
@@ -84,6 +98,10 @@ static char *fill_origin_blob(struct origin *o, mmfile_t *file)
        return file->ptr;
 }
 
+/*
+ * Origin is refcounted and usually we keep the blob contents to be
+ * reused.
+ */
 static inline struct origin *origin_incref(struct origin *o)
 {
        if (o)
@@ -101,6 +119,11 @@ static void origin_decref(struct origin *o)
        }
 }
 
+/*
+ * 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.
+ */
 struct blame_entry {
        struct blame_entry *prev;
        struct blame_entry *next;
@@ -127,19 +150,24 @@ struct blame_entry {
        int s_lno;
 
        /* how significant this entry is -- cached to avoid
-        * scanning the lines over and over
+        * scanning the lines over and over.
         */
        unsigned score;
 };
 
+/*
+ * The current state of the blame assignment.
+ */
 struct scoreboard {
        /* the final commit (i.e. where we started digging from) */
        struct commit *final;
 
        const char *path;
 
-       /* the contents in the final; pointed into by buf pointers of
-        * blame_entries
+       /*
+        * The contents in the final image.
+        * Used by many functions to obtain contents of the nth line,
+        * indexed with scoreboard.lineno[blame_entry.lno].
         */
        const char *final_buf;
        unsigned long final_buf_size;
@@ -152,24 +180,28 @@ struct scoreboard {
        int *lineno;
 };
 
-static int cmp_suspect(struct origin *a, struct origin *b)
+static inline int same_suspect(struct origin *a, struct origin *b)
 {
-       int cmp = hashcmp(a->commit->object.sha1, b->commit->object.sha1);
-       if (cmp)
-               return cmp;
-       return strcmp(a->path, b->path);
+       if (a == b)
+               return 1;
+       if (a->commit != b->commit)
+               return 0;
+       return !strcmp(a->path, b->path);
 }
 
-#define cmp_suspect(a, b) ( ((a)==(b)) ? 0 : cmp_suspect(a,b) )
-
 static void sanity_check_refcnt(struct scoreboard *);
 
+/*
+ * If two blame entries that are next to each other came from
+ * contiguous lines in the same origin (i.e. <commit, path> pair),
+ * merge them together.
+ */
 static void coalesce(struct scoreboard *sb)
 {
        struct blame_entry *ent, *next;
 
        for (ent = sb->ent; ent && (next = ent->next); ent = next) {
-               if (!cmp_suspect(ent->suspect, next->suspect) &&
+               if (same_suspect(ent->suspect, next->suspect) &&
                    ent->guilty == next->guilty &&
                    ent->s_lno + ent->num_lines == next->s_lno) {
                        ent->num_lines += next->num_lines;
@@ -187,6 +219,12 @@ static void coalesce(struct scoreboard *sb)
                sanity_check_refcnt(sb);
 }
 
+/*
+ * Given a commit and a path in it, create a new origin structure.
+ * The callers that add blame to the scoreboard should use
+ * get_origin() to obtain shared, refcounted copy instead of calling
+ * this function directly.
+ */
 static struct origin *make_origin(struct commit *commit, const char *path)
 {
        struct origin *o;
@@ -197,6 +235,9 @@ static struct origin *make_origin(struct commit *commit, const char *path)
        return o;
 }
 
+/*
+ * Locate an existing origin or create a new one.
+ */
 static struct origin *get_origin(struct scoreboard *sb,
                                 struct commit *commit,
                                 const char *path)
@@ -211,10 +252,16 @@ static struct origin *get_origin(struct scoreboard *sb,
        return make_origin(commit, path);
 }
 
+/*
+ * Fill the blob_sha1 field of an origin if it hasn't, so that later
+ * call to fill_origin_blob() can use it to locate the data.  blob_sha1
+ * for an origin is also used to pass the blame for the entire file to
+ * the parent to detect the case where a child's blob is identical to
+ * that of its parent's.
+ */
 static int fill_blob_sha1(struct origin *origin)
 {
        unsigned mode;
-       char type[10];
 
        if (!is_null_sha1(origin->blob_sha1))
                return 0;
@@ -222,8 +269,7 @@ static int fill_blob_sha1(struct origin *origin)
                           origin->path,
                           origin->blob_sha1, &mode))
                goto error_out;
-       if (sha1_object_info(origin->blob_sha1, type, NULL) ||
-           strcmp(type, blob_type))
+       if (sha1_object_info(origin->blob_sha1, NULL) != OBJ_BLOB)
                goto error_out;
        return 0;
  error_out:
@@ -231,6 +277,10 @@ static int fill_blob_sha1(struct origin *origin)
        return -1;
 }
 
+/*
+ * We have an origin -- check if the same path exists in the
+ * parent and return an origin structure to represent it.
+ */
 static struct origin *find_origin(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
@@ -240,12 +290,26 @@ static struct origin *find_origin(struct scoreboard *sb,
        const char *paths[2];
 
        if (parent->util) {
-               /* This is a freestanding copy of origin and not
-                * refcounted.
+               /*
+                * 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)) {
+                       /*
+                        * 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,
+                        * so copy it.  Otherwise porigin was in the
+                        * scoreboard and already knows blob_sha1.
+                        */
                        if (porigin->refcnt == 1)
                                hashcpy(porigin->blob_sha1, cached->blob_sha1);
                        return porigin;
@@ -269,9 +333,13 @@ static struct origin *find_origin(struct scoreboard *sb,
        diff_tree_setup_paths(paths, &diff_opts);
        if (diff_setup_done(&diff_opts) < 0)
                die("diff-setup");
-       diff_tree_sha1(parent->tree->object.sha1,
-                      origin->commit->tree->object.sha1,
-                      "", &diff_opts);
+
+       if (is_null_sha1(origin->commit->object.sha1))
+               do_diff_cache(parent->tree->object.sha1, &diff_opts);
+       else
+               diff_tree_sha1(parent->tree->object.sha1,
+                              origin->commit->tree->object.sha1,
+                              "", &diff_opts);
        diffcore_std(&diff_opts);
 
        /* It is either one entry that says "modified", or "created",
@@ -302,7 +370,13 @@ static struct origin *find_origin(struct scoreboard *sb,
        }
        diff_flush(&diff_opts);
        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);
                parent->util = cached;
@@ -310,6 +384,10 @@ static struct origin *find_origin(struct scoreboard *sb,
        return porigin;
 }
 
+/*
+ * We have an origin -- find the path that corresponds to it in its
+ * parent and return an origin structure to represent it.
+ */
 static struct origin *find_rename(struct scoreboard *sb,
                                  struct commit *parent,
                                  struct origin *origin)
@@ -328,9 +406,13 @@ static struct origin *find_rename(struct scoreboard *sb,
        diff_tree_setup_paths(paths, &diff_opts);
        if (diff_setup_done(&diff_opts) < 0)
                die("diff-setup");
-       diff_tree_sha1(parent->tree->object.sha1,
-                      origin->commit->tree->object.sha1,
-                      "", &diff_opts);
+
+       if (is_null_sha1(origin->commit->object.sha1))
+               do_diff_cache(parent->tree->object.sha1, &diff_opts);
+       else
+               diff_tree_sha1(parent->tree->object.sha1,
+                              origin->commit->tree->object.sha1,
+                              "", &diff_opts);
        diffcore_std(&diff_opts);
 
        for (i = 0; i < diff_queued_diff.nr; i++) {
@@ -346,6 +428,9 @@ static struct origin *find_rename(struct scoreboard *sb,
        return porigin;
 }
 
+/*
+ * Parsing of patch chunks...
+ */
 struct chunk {
        /* line number in postimage; up to but not including this
         * line is the same as preimage
@@ -447,6 +532,11 @@ static struct patch *compare_buffer(mmfile_t *file_p, mmfile_t *file_o,
        return state.ret;
 }
 
+/*
+ * Run diff between two origins and grab the patch output, so that
+ * we can pass blame for lines origin is currently suspected for
+ * to its parent.
+ */
 static struct patch *get_patch(struct origin *parent, struct origin *origin)
 {
        mmfile_t file_p, file_o;
@@ -467,6 +557,10 @@ static void free_patch(struct patch *p)
        free(p);
 }
 
+/*
+ * Link in a new blame entry to the scoreboard.  Entries that cover the
+ * same line range have been removed from the scoreboard previously.
+ */
 static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
 {
        struct blame_entry *ent, *prev = NULL;
@@ -490,6 +584,12 @@ static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
                e->next->prev = e;
 }
 
+/*
+ * src typically is on-stack; we want to copy the information in it to
+ * an 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.
+ */
 static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
 {
        struct blame_entry *p, *n;
@@ -509,25 +609,25 @@ static const char *nth_line(struct scoreboard *sb, int lno)
        return sb->final_buf + sb->lineno[lno];
 }
 
+/*
+ * It is known that lines between tlno to same came from parent, and e
+ * has an overlap with that range.  it also is known that parent's
+ * line plno corresponds to e's line tlno.
+ *
+ *                <---- e ----->
+ *                   <------>
+ *                   <------------>
+ *             <------------>
+ *             <------------------>
+ *
+ * Split e into potentially three parts; before this chunk, the chunk
+ * to be blamed for the parent, and after that portion.
+ */
 static void split_overlap(struct blame_entry *split,
                          struct blame_entry *e,
                          int tlno, int plno, int same,
                          struct origin *parent)
 {
-       /* it is known that lines between tlno to same came from
-        * parent, and e has an overlap with that range.  it also is
-        * known that parent's line plno corresponds to e's line tlno.
-        *
-        *                <---- e ----->
-        *                   <------>
-        *                   <------------>
-        *             <------------>
-        *             <------------------>
-        *
-        * Potentially we need to split e into three parts; before
-        * this chunk, the chunk to be blamed for parent, and after
-        * that portion.
-        */
        int chunk_end_lno;
        memset(split, 0, sizeof(struct blame_entry [3]));
 
@@ -557,11 +657,20 @@ static void split_overlap(struct blame_entry *split,
                chunk_end_lno = e->lno + e->num_lines;
        split[1].num_lines = chunk_end_lno - split[1].lno;
 
+       /*
+        * if it turns out there is nothing to blame the parent for,
+        * forget about the splitting.  !split[1].suspect signals this.
+        */
        if (split[1].num_lines < 1)
                return;
        split[1].suspect = origin_incref(parent);
 }
 
+/*
+ * split_overlap() divided an existing blame e into up to three parts
+ * in split.  Adjust the linked list of blames in the scoreboard to
+ * reflect the split.
+ */
 static void split_blame(struct scoreboard *sb,
                        struct blame_entry *split,
                        struct blame_entry *e)
@@ -569,21 +678,27 @@ static void split_blame(struct scoreboard *sb,
        struct blame_entry *new_entry;
 
        if (split[0].suspect && split[2].suspect) {
-               /* we need to split e into two and add another for parent */
+               /* The first part (reuse storage for the existing entry e) */
                dup_entry(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);
 
+               /* ... 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);
        }
        else if (!split[0].suspect && !split[2].suspect)
-               /* parent covers the entire area */
+               /*
+                * The parent covers the entire area; reuse storage for
+                * e and replace it with the parent.
+                */
                dup_entry(e, &split[1]);
        else if (split[0].suspect) {
+               /* me and then parent */
                dup_entry(e, &split[0]);
 
                new_entry = xmalloc(sizeof(*new_entry));
@@ -591,6 +706,7 @@ static void split_blame(struct scoreboard *sb,
                add_blame_entry(sb, new_entry);
        }
        else {
+               /* parent and then me */
                dup_entry(e, &split[1]);
 
                new_entry = xmalloc(sizeof(*new_entry));
@@ -621,6 +737,10 @@ static void split_blame(struct scoreboard *sb,
        }
 }
 
+/*
+ * After splitting the blame, the origins used by the
+ * on-stack blame_entry should lose one refcnt each.
+ */
 static void decref_split(struct blame_entry *split)
 {
        int i;
@@ -629,6 +749,10 @@ static void decref_split(struct blame_entry *split)
                origin_decref(split[i].suspect);
 }
 
+/*
+ * Helper for blame_chunk().  blame_entry e is known to overlap with
+ * the patch hunk; split it and pass blame to the parent.
+ */
 static void blame_overlap(struct scoreboard *sb, struct blame_entry *e,
                          int tlno, int plno, int same,
                          struct origin *parent)
@@ -641,13 +765,16 @@ static void blame_overlap(struct scoreboard *sb, struct blame_entry *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)
 {
        struct blame_entry *e;
        int last_in_target = -1;
 
        for (e = sb->ent; e; e = e->next) {
-               if (e->guilty || cmp_suspect(e->suspect, target))
+               if (e->guilty || !same_suspect(e->suspect, target))
                        continue;
                if (last_in_target < e->s_lno + e->num_lines)
                        last_in_target = e->s_lno + e->num_lines;
@@ -655,6 +782,11 @@ static int find_last_in_target(struct scoreboard *sb, struct origin *target)
        return last_in_target;
 }
 
+/*
+ * 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.
+ */
 static void blame_chunk(struct scoreboard *sb,
                        int tlno, int plno, int same,
                        struct origin *target, struct origin *parent)
@@ -662,7 +794,7 @@ static void blame_chunk(struct scoreboard *sb,
        struct blame_entry *e;
 
        for (e = sb->ent; e; e = e->next) {
-               if (e->guilty || cmp_suspect(e->suspect, target))
+               if (e->guilty || !same_suspect(e->suspect, target))
                        continue;
                if (same <= e->s_lno)
                        continue;
@@ -671,6 +803,11 @@ static void blame_chunk(struct scoreboard *sb,
        }
 }
 
+/*
+ * We are looking at the origin 'target' and aiming to pass blame
+ * 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)
@@ -691,13 +828,22 @@ static int pass_blame_to_parent(struct scoreboard *sb,
                plno = chunk->p_next;
                tlno = chunk->t_next;
        }
-       /* rest (i.e. anything above tlno) are the same as parent */
+       /* The rest (i.e. anything after tlno) are the same as the parent */
        blame_chunk(sb, tlno, plno, last_in_target, target, parent);
 
        free_patch(patch);
        return 0;
 }
 
+/*
+ * The lines in blame_entry after splitting blames many times can become
+ * very small and trivial, and at some point it becomes pointless to
+ * blame the parents.  E.g. "\t\t}\n\t}\n\n" appears everywhere in any
+ * ordinary C program, and it is not worth to say it was copied from
+ * totally unrelated file in the parent.
+ *
+ * Compute how trivial the lines in the blame_entry are.
+ */
 static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
 {
        unsigned score;
@@ -719,6 +865,12 @@ static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
        return score;
 }
 
+/*
+ * best_so_far[] and this[] are both a split of an existing blame_entry
+ * that passes blame to the parent.  Maintain best_so_far the best split
+ * so far, by comparing this and best_so_far and copying this into
+ * bst_so_far as needed.
+ */
 static void copy_split_if_better(struct scoreboard *sb,
                                 struct blame_entry *best_so_far,
                                 struct blame_entry *this)
@@ -738,6 +890,11 @@ static void copy_split_if_better(struct scoreboard *sb,
        memcpy(best_so_far, this, sizeof(struct blame_entry [3]));
 }
 
+/*
+ * Find the lines from parent that are the same as ent so that
+ * we can pass blames to it.  file_p has the blob contents for
+ * the parent.
+ */
 static void find_copy_in_blob(struct scoreboard *sb,
                              struct blame_entry *ent,
                              struct origin *parent,
@@ -750,6 +907,9 @@ static void find_copy_in_blob(struct scoreboard *sb,
        struct patch *patch;
        int i, plno, tlno;
 
+       /*
+        * Prepare mmfile that contains only the lines in ent.
+        */
        cp = nth_line(sb, ent->lno);
        file_o.ptr = (char*) cp;
        cnt = ent->num_lines;
@@ -785,6 +945,10 @@ static void find_copy_in_blob(struct scoreboard *sb,
        free_patch(patch);
 }
 
+/*
+ * 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)
@@ -805,7 +969,7 @@ static int find_move_in_parent(struct scoreboard *sb,
        while (made_progress) {
                made_progress = 0;
                for (e = sb->ent; e; e = e->next) {
-                       if (e->guilty || cmp_suspect(e->suspect, target))
+                       if (e->guilty || !same_suspect(e->suspect, target))
                                continue;
                        find_copy_in_blob(sb, e, parent, split, &file_p);
                        if (split[1].suspect &&
@@ -819,12 +983,15 @@ static int find_move_in_parent(struct scoreboard *sb,
        return 0;
 }
 
-
 struct blame_list {
        struct blame_entry *ent;
        struct blame_entry split[3];
 };
 
+/*
+ * 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 *num_ents_p)
@@ -833,22 +1000,24 @@ static struct blame_list *setup_blame_list(struct scoreboard *sb,
        int num_ents, i;
        struct blame_list *blame_list = NULL;
 
-       /* Count the number of entries the target is suspected for,
-        * and prepare a list of entry and the best split.
-        */
        for (e = sb->ent, num_ents = 0; e; e = e->next)
-               if (!e->guilty && !cmp_suspect(e->suspect, target))
+               if (!e->guilty && same_suspect(e->suspect, target))
                        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->guilty && !cmp_suspect(e->suspect, target))
+                       if (!e->guilty && same_suspect(e->suspect, target))
                                blame_list[i++].ent = e;
        }
        *num_ents_p = num_ents;
        return blame_list;
 }
 
+/*
+ * 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,
@@ -886,9 +1055,12 @@ static int find_copy_in_parent(struct scoreboard *sb,
            (!porigin || strcmp(target->path, porigin->path)))
                diff_opts.find_copies_harder = 1;
 
-       diff_tree_sha1(parent->tree->object.sha1,
-                      target->commit->tree->object.sha1,
-                      "", &diff_opts);
+       if (is_null_sha1(target->commit->object.sha1))
+               do_diff_cache(parent->tree->object.sha1, &diff_opts);
+       else
+               diff_tree_sha1(parent->tree->object.sha1,
+                              target->commit->tree->object.sha1,
+                              "", &diff_opts);
 
        if (!diff_opts.find_copies_harder)
                diffcore_std(&diff_opts);
@@ -949,7 +1121,8 @@ static int find_copy_in_parent(struct scoreboard *sb,
        return retval;
 }
 
-/* The blobs of origin and porigin exactly match, so everything
+/*
+ * The blobs of origin and porigin exactly match, so everything
  * origin is suspected for can be blamed on the parent.
  */
 static void pass_whole_blame(struct scoreboard *sb,
@@ -963,7 +1136,7 @@ static void pass_whole_blame(struct scoreboard *sb,
                origin->file.ptr = NULL;
        }
        for (e = sb->ent; e; e = e->next) {
-               if (cmp_suspect(e->suspect, origin))
+               if (!same_suspect(e->suspect, origin))
                        continue;
                origin_incref(porigin);
                origin_decref(e->suspect);
@@ -1034,7 +1207,7 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
        }
 
        /*
-        * Optionally run "miff" to find moves in parents' files here.
+        * Optionally find moves in parents' files.
         */
        if (opt & PICKAXE_BLAME_MOVE)
                for (i = 0, parent = commit->parents;
@@ -1048,7 +1221,7 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
                }
 
        /*
-        * Optionally run "ciff" to find copies from parents' files here.
+        * Optionally find copies from parents' files.
         */
        if (opt & PICKAXE_BLAME_COPY)
                for (i = 0, parent = commit->parents;
@@ -1065,88 +1238,31 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
                origin_decref(parent_origin[i]);
 }
 
-static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
-{
-       while (1) {
-               struct blame_entry *ent;
-               struct commit *commit;
-               struct origin *suspect = NULL;
-
-               /* 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 */
-
-               origin_incref(suspect);
-               commit = suspect->commit;
-               if (!commit->object.parsed)
-                       parse_commit(commit);
-               if (!(commit->object.flags & UNINTERESTING) &&
-                   !(revs->max_age != -1 && commit->date  < revs->max_age))
-                       pass_blame(sb, suspect, opt);
-               else {
-                       commit->object.flags |= UNINTERESTING;
-                       if (commit->object.parsed)
-                               mark_parents_uninteresting(commit);
-               }
-
-               /* Take responsibility for the remaining entries */
-               for (ent = sb->ent; ent; ent = ent->next)
-                       if (!cmp_suspect(ent->suspect, suspect))
-                               ent->guilty = 1;
-               origin_decref(suspect);
-
-               if (DEBUG) /* sanity */
-                       sanity_check_refcnt(sb);
-       }
-}
-
-static const char *format_time(unsigned long time, const char *tz_str,
-                              int show_raw_time)
-{
-       static char time_buf[128];
-       time_t t = time;
-       int minutes, tz;
-       struct tm *tm;
-
-       if (show_raw_time) {
-               sprintf(time_buf, "%lu %s", time, tz_str);
-               return time_buf;
-       }
-
-       tz = atoi(tz_str);
-       minutes = tz < 0 ? -tz : tz;
-       minutes = (minutes / 100)*60 + (minutes % 100);
-       minutes = tz < 0 ? -minutes : minutes;
-       t = time + minutes * 60;
-       tm = gmtime(&t);
-
-       strftime(time_buf, sizeof(time_buf), "%Y-%m-%d %H:%M:%S ", tm);
-       strcat(time_buf, tz_str);
-       return time_buf;
-}
-
+/*
+ * Information on commits, used for output.
+ */
 struct commit_info
 {
-       char *author;
-       char *author_mail;
+       const char *author;
+       const char *author_mail;
        unsigned long author_time;
-       char *author_tz;
+       const char *author_tz;
 
        /* filled only when asked for details */
-       char *committer;
-       char *committer_mail;
+       const char *committer;
+       const char *committer_mail;
        unsigned long committer_time;
-       char *committer_tz;
+       const char *committer_tz;
 
-       char *summary;
+       const char *summary;
 };
 
+/*
+ * Parse author/committer line in the commit object buffer
+ */
 static void get_ac_line(const char *inbuf, const char *what,
-                       int bufsz, char *person, char **mail,
-                       unsigned long *time, char **tz)
+                       int bufsz, char *person, const char **mail,
+                       unsigned long *time, const char **tz)
 {
        int len;
        char *tmp, *endp;
@@ -1163,7 +1279,7 @@ static void get_ac_line(const char *inbuf, const char *what,
        if (bufsz <= len) {
        error_out:
                /* Ugh */
-               person = *mail = *tz = "(unknown)";
+               *mail = *tz = "(unknown)";
                *time = 0;
                return;
        }
@@ -1198,14 +1314,15 @@ static void get_commit_info(struct commit *commit,
        static char committer_buf[1024];
        static char summary_buf[1024];
 
-       /* We've operated without save_commit_buffer, so
+       /*
+        * We've operated without save_commit_buffer, so
         * we now need to populate them for output.
         */
        if (!commit->buffer) {
-               char type[20];
+               enum object_type type;
                unsigned long size;
                commit->buffer =
-                       read_sha1_file(commit->object.sha1, type, &size);
+                       read_sha1_file(commit->object.sha1, &type, &size);
        }
        ret->author = author_buf;
        get_ac_line(commit->buffer, "\nauthor ",
@@ -1230,14 +1347,135 @@ static void get_commit_info(struct commit *commit,
        tmp += 2;
        endp = strchr(tmp, '\n');
        if (!endp)
-               goto error_out;
+               endp = tmp + strlen(tmp);
        len = endp - tmp;
-       if (len >= sizeof(summary_buf))
+       if (len >= sizeof(summary_buf) || len == 0)
                goto error_out;
        memcpy(summary_buf, tmp, len);
        summary_buf[len] = 0;
 }
 
+/*
+ * To allow LF and other nonportable characters in pathnames,
+ * they are c-style quoted as needed.
+ */
+static void write_filename_info(const char *path)
+{
+       printf("filename ");
+       write_name_quoted(NULL, 0, path, 1, stdout);
+       putchar('\n');
+}
+
+/*
+ * The blame_entry is found to be guilty for the range.  Mark it
+ * as such, and 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;
+
+               printf("%s %d %d %d\n",
+                      sha1_to_hex(suspect->commit->object.sha1),
+                      ent->s_lno + 1, ent->lno + 1, ent->num_lines);
+               if (!(suspect->commit->object.flags & METAINFO_SHOWN)) {
+                       struct commit_info ci;
+                       suspect->commit->object.flags |= METAINFO_SHOWN;
+                       get_commit_info(suspect->commit, &ci, 1);
+                       printf("author %s\n", ci.author);
+                       printf("author-mail %s\n", ci.author_mail);
+                       printf("author-time %lu\n", ci.author_time);
+                       printf("author-tz %s\n", ci.author_tz);
+                       printf("committer %s\n", ci.committer);
+                       printf("committer-mail %s\n", ci.committer_mail);
+                       printf("committer-time %lu\n", ci.committer_time);
+                       printf("committer-tz %s\n", ci.committer_tz);
+                       printf("summary %s\n", ci.summary);
+                       if (suspect->commit->object.flags & UNINTERESTING)
+                               printf("boundary\n");
+               }
+               write_filename_info(suspect->path);
+       }
+}
+
+/*
+ * 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.
+ */
+static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
+{
+       while (1) {
+               struct blame_entry *ent;
+               struct commit *commit;
+               struct origin *suspect = NULL;
+
+               /* 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 */
+
+               /*
+                * We will use this suspect later in the loop,
+                * so hold onto it in the meantime.
+                */
+               origin_incref(suspect);
+               commit = suspect->commit;
+               if (!commit->object.parsed)
+                       parse_commit(commit);
+               if (!(commit->object.flags & UNINTERESTING) &&
+                   !(revs->max_age != -1 && commit->date < revs->max_age))
+                       pass_blame(sb, suspect, opt);
+               else {
+                       commit->object.flags |= UNINTERESTING;
+                       if (commit->object.parsed)
+                               mark_parents_uninteresting(commit);
+               }
+               /* treat root commit as boundary */
+               if (!commit->parents && !show_root)
+                       commit->object.flags |= UNINTERESTING;
+
+               /* Take responsibility for the remaining entries */
+               for (ent = sb->ent; ent; ent = ent->next)
+                       if (same_suspect(ent->suspect, suspect))
+                               found_guilty_entry(ent);
+               origin_decref(suspect);
+
+               if (DEBUG) /* sanity */
+                       sanity_check_refcnt(sb);
+       }
+}
+
+static const char *format_time(unsigned long time, const char *tz_str,
+                              int show_raw_time)
+{
+       static char time_buf[128];
+       time_t t = time;
+       int minutes, tz;
+       struct tm *tm;
+
+       if (show_raw_time) {
+               sprintf(time_buf, "%lu %s", time, tz_str);
+               return time_buf;
+       }
+
+       tz = atoi(tz_str);
+       minutes = tz < 0 ? -tz : tz;
+       minutes = (minutes / 100)*60 + (minutes % 100);
+       minutes = tz < 0 ? -minutes : minutes;
+       t = time + minutes * 60;
+       tm = gmtime(&t);
+
+       strftime(time_buf, sizeof(time_buf), "%Y-%m-%d %H:%M:%S ", tm);
+       strcat(time_buf, tz_str);
+       return time_buf;
+}
+
 #define OUTPUT_ANNOTATE_COMPAT 001
 #define OUTPUT_LONG_OBJECT_NAME        002
 #define OUTPUT_RAW_TIMESTAMP   004
@@ -1272,13 +1510,13 @@ static void emit_porcelain(struct scoreboard *sb, struct blame_entry *ent)
                printf("committer-mail %s\n", ci.committer_mail);
                printf("committer-time %lu\n", ci.committer_time);
                printf("committer-tz %s\n", ci.committer_tz);
-               printf("filename %s\n", suspect->path);
+               write_filename_info(suspect->path);
                printf("summary %s\n", ci.summary);
                if (suspect->commit->object.flags & UNINTERESTING)
                        printf("boundary\n");
        }
        else if (suspect->commit->object.flags & MORE_THAN_ONE_PATH)
-               printf("filename %s\n", suspect->path);
+               write_filename_info(suspect->path);
 
        cp = nth_line(sb, ent->lno);
        for (cnt = 0; cnt < ent->num_lines; cnt++) {
@@ -1314,8 +1552,12 @@ static void emit_other(struct scoreboard *sb, struct blame_entry *ent, int opt)
                int length = (opt & OUTPUT_LONG_OBJECT_NAME) ? 40 : 8;
 
                if (suspect->commit->object.flags & UNINTERESTING) {
-                       length--;
-                       putchar('^');
+                       if (blank_boundary)
+                               memset(hex, ' ', length);
+                       else if (!cmd_is_annotate) {
+                               length--;
+                               putchar('^');
+                       }
                }
 
                printf("%.*s", length, hex);
@@ -1379,6 +1621,10 @@ static void output(struct scoreboard *sb, int option)
        }
 }
 
+/*
+ * To allow quick access to the contents of nth line in the
+ * final image, prepare an index in the scoreboard.
+ */
 static int prepare_lines(struct scoreboard *sb)
 {
        const char *buf = sb->final_buf;
@@ -1406,6 +1652,11 @@ static int prepare_lines(struct scoreboard *sb)
        return sb->num_lines;
 }
 
+/*
+ * Add phony grafts for use with -S; this is primarily to
+ * support git-cvsserver that wants to give a linear history
+ * to its clients.
+ */
 static int read_ancestry(const char *graft_file)
 {
        FILE *fp = fopen(graft_file, "r");
@@ -1423,6 +1674,9 @@ static int read_ancestry(const char *graft_file)
        return 0;
 }
 
+/*
+ * How many columns do we need to show line numbers in decimal?
+ */
 static int lineno_width(int lines)
 {
         int i, width;
@@ -1432,6 +1686,10 @@ static int lineno_width(int lines)
         return width;
 }
 
+/*
+ * How many columns do we need to show line numbers, authors,
+ * and filenames?
+ */
 static void find_alignment(struct scoreboard *sb, int *option)
 {
        int longest_src_lines = 0;
@@ -1470,6 +1728,10 @@ static void find_alignment(struct scoreboard *sb, int *option)
        max_score_digits = lineno_width(largest_score);
 }
 
+/*
+ * For debugging -- origin is refcounted, and this asserts that
+ * we do not underflow.
+ */
 static void sanity_check_refcnt(struct scoreboard *sb)
 {
        int baa = 0;
@@ -1491,8 +1753,9 @@ static void sanity_check_refcnt(struct scoreboard *sb)
                        ent->suspect->refcnt = -ent->suspect->refcnt;
        }
        for (ent = sb->ent; ent; ent = ent->next) {
-               /* then pick each and see if they have the the correct
-                * refcnt.
+               /*
+                * ... then pick each and see if they have the the
+                * correct refcnt.
                 */
                int found;
                struct blame_entry *e;
@@ -1522,6 +1785,10 @@ static void sanity_check_refcnt(struct scoreboard *sb)
        }
 }
 
+/*
+ * Used for the command line parsing; check if the path exists
+ * in the working tree.
+ */
 static int has_path_in_work_tree(const char *path)
 {
        struct stat st;
@@ -1544,6 +1811,9 @@ static const char *add_prefix(const char *prefix, const char *path)
        return prefix_path(prefix, strlen(prefix), path);
 }
 
+/*
+ * Parsing of (comma separated) one item in the -L option
+ */
 static const char *parse_loc(const char *spec,
                             struct scoreboard *sb, long lno,
                             long begin, long *ret)
@@ -1618,6 +1888,9 @@ static const char *parse_loc(const char *spec,
        }
 }
 
+/*
+ * Parsing of -L option
+ */
 static void prepare_blame_range(struct scoreboard *sb,
                                const char *bottomtop,
                                long lno,
@@ -1635,6 +1908,150 @@ static void prepare_blame_range(struct scoreboard *sb,
                usage(blame_usage);
 }
 
+static int git_blame_config(const char *var, const char *value)
+{
+       if (!strcmp(var, "blame.showroot")) {
+               show_root = git_config_bool(var, value);
+               return 0;
+       }
+       if (!strcmp(var, "blame.blankboundary")) {
+               blank_boundary = git_config_bool(var, value);
+               return 0;
+       }
+       return git_default_config(var, value);
+}
+
+static struct commit *fake_working_tree_commit(const char *path, const char *contents_from)
+{
+       struct commit *commit;
+       struct origin *origin;
+       unsigned char head_sha1[20];
+       char *buf;
+       const char *ident;
+       int fd;
+       time_t now;
+       unsigned long fin_size;
+       int size, len;
+       struct cache_entry *ce;
+       unsigned mode;
+
+       if (get_sha1("HEAD", head_sha1))
+               die("No such ref: HEAD");
+
+       time(&now);
+       commit = xcalloc(1, sizeof(*commit));
+       commit->parents = xcalloc(1, sizeof(*commit->parents));
+       commit->parents->item = lookup_commit_reference(head_sha1);
+       commit->object.parsed = 1;
+       commit->date = now;
+       commit->object.type = OBJ_COMMIT;
+
+       origin = make_origin(commit, path);
+
+       if (!contents_from || strcmp("-", contents_from)) {
+               struct stat st;
+               const char *read_from;
+
+               if (contents_from) {
+                       if (stat(contents_from, &st) < 0)
+                               die("Cannot stat %s", contents_from);
+                       read_from = contents_from;
+               }
+               else {
+                       if (lstat(path, &st) < 0)
+                               die("Cannot lstat %s", path);
+                       read_from = path;
+               }
+               fin_size = xsize_t(st.st_size);
+               buf = xmalloc(fin_size+1);
+               mode = canon_mode(st.st_mode);
+               switch (st.st_mode & S_IFMT) {
+               case S_IFREG:
+                       fd = open(read_from, O_RDONLY);
+                       if (fd < 0)
+                               die("cannot open %s", read_from);
+                       if (read_in_full(fd, buf, fin_size) != fin_size)
+                               die("cannot read %s", read_from);
+                       break;
+               case S_IFLNK:
+                       if (readlink(read_from, buf, fin_size+1) != fin_size)
+                               die("cannot readlink %s", read_from);
+                       break;
+               default:
+                       die("unsupported file type %s", read_from);
+               }
+       }
+       else {
+               /* Reading from stdin */
+               contents_from = "standard input";
+               buf = NULL;
+               fin_size = 0;
+               mode = 0;
+               while (1) {
+                       ssize_t cnt = 8192;
+                       buf = xrealloc(buf, fin_size + cnt);
+                       cnt = xread(0, buf + fin_size, cnt);
+                       if (cnt < 0)
+                               die("read error %s from stdin",
+                                   strerror(errno));
+                       if (!cnt)
+                               break;
+                       fin_size += cnt;
+               }
+               buf = xrealloc(buf, fin_size + 1);
+       }
+       buf[fin_size] = 0;
+       origin->file.ptr = buf;
+       origin->file.size = fin_size;
+       pretend_sha1_file(buf, fin_size, OBJ_BLOB, origin->blob_sha1);
+       commit->util = origin;
+
+       /*
+        * Read the current index, replace the path entry with
+        * origin->blob_sha1 without mucking with its mode or type
+        * bits; we are not going to write this index out -- we just
+        * want to run "diff-index --cached".
+        */
+       discard_cache();
+       read_cache();
+
+       len = strlen(path);
+       if (!mode) {
+               int pos = cache_name_pos(path, len);
+               if (0 <= pos)
+                       mode = ntohl(active_cache[pos]->ce_mode);
+               else
+                       /* Let's not bother reading from HEAD tree */
+                       mode = S_IFREG | 0644;
+       }
+       size = cache_entry_size(len);
+       ce = xcalloc(1, size);
+       hashcpy(ce->sha1, origin->blob_sha1);
+       memcpy(ce->name, path, len);
+       ce->ce_flags = create_ce_flags(len, 0);
+       ce->ce_mode = create_ce_mode(mode);
+       add_cache_entry(ce, ADD_CACHE_OK_TO_ADD|ADD_CACHE_OK_TO_REPLACE);
+
+       /*
+        * We are not going to write this out, so this does not matter
+        * right now, but someday we might optimize diff-index --cached
+        * with cache-tree information.
+        */
+       cache_tree_invalidate_path(active_cache_tree, path);
+
+       commit->buffer = xmalloc(400);
+       ident = fmt_ident("Not Committed Yet", "not.committed.yet", NULL, 0);
+       sprintf(commit->buffer,
+               "tree 0000000000000000000000000000000000000000\n"
+               "parent %s\n"
+               "author %s\n"
+               "committer %s\n\n"
+               "Version of %s from %s\n",
+               sha1_to_hex(head_sha1),
+               ident, ident, path, contents_from ? contents_from : path);
+       return commit;
+}
+
 int cmd_blame(int argc, const char **argv, const char *prefix)
 {
        struct rev_info revs;
@@ -1645,11 +2062,16 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
        int i, seen_dashdash, unk, opt;
        long bottom, top, lno;
        int output_option = 0;
+       int show_stats = 0;
        const char *revs_file = NULL;
        const char *final_commit_name = NULL;
-       char type[10];
+       enum object_type type;
        const char *bottomtop = NULL;
+       const char *contents_from = NULL;
+
+       cmd_is_annotate = !strcmp(argv[0], "annotate");
 
+       git_config(git_blame_config);
        save_commit_buffer = 0;
 
        opt = 0;
@@ -1658,6 +2080,12 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                const char *arg = argv[i];
                if (*arg != '-')
                        break;
+               else if (!strcmp("-b", arg))
+                       blank_boundary = 1;
+               else if (!strcmp("--root", arg))
+                       show_root = 1;
+               else if (!strcmp(arg, "--show-stats"))
+                       show_stats = 1;
                else if (!strcmp("-c", arg))
                        output_option |= OUTPUT_ANNOTATE_COMPAT;
                else if (!strcmp("-t", arg))
@@ -1666,17 +2094,17 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                        output_option |= OUTPUT_LONG_OBJECT_NAME;
                else if (!strcmp("-S", arg) && ++i < argc)
                        revs_file = argv[i];
-               else if (!strncmp("-M", arg, 2)) {
+               else if (!prefixcmp(arg, "-M")) {
                        opt |= PICKAXE_BLAME_MOVE;
                        blame_move_score = parse_score(arg+2);
                }
-               else if (!strncmp("-C", arg, 2)) {
+               else if (!prefixcmp(arg, "-C")) {
                        if (opt & PICKAXE_BLAME_COPY)
                                opt |= PICKAXE_BLAME_COPY_HARDER;
                        opt |= PICKAXE_BLAME_COPY | PICKAXE_BLAME_MOVE;
                        blame_copy_score = parse_score(arg+2);
                }
-               else if (!strncmp("-L", arg, 2)) {
+               else if (!prefixcmp(arg, "-L")) {
                        if (!arg[2]) {
                                if (++i >= argc)
                                        usage(blame_usage);
@@ -1688,6 +2116,13 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                                die("More than one '-L n,m' option given");
                        bottomtop = arg;
                }
+               else if (!strcmp("--contents", arg)) {
+                       if (++i >= argc)
+                               usage(blame_usage);
+                       contents_from = argv[i];
+               }
+               else if (!strcmp("--incremental", arg))
+                       incremental = 1;
                else if (!strcmp("--score-debug", arg))
                        output_option |= OUTPUT_SHOW_SCORE;
                else if (!strcmp("-f", arg) ||
@@ -1708,14 +2143,18 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                        argv[unk++] = arg;
        }
 
+       if (!incremental)
+               setup_pager();
+
        if (!blame_move_score)
                blame_move_score = BLAME_DEFAULT_MOVE_SCORE;
        if (!blame_copy_score)
                blame_copy_score = BLAME_DEFAULT_COPY_SCORE;
 
-       /* We have collected options unknown to us in argv[1..unk]
+       /*
+        * We have collected options unknown to us in argv[1..unk]
         * which are to be passed to revision machinery if we are
-        * going to do the "bottom" procesing.
+        * going to do the "bottom" processing.
         *
         * The remaining are:
         *
@@ -1761,6 +2200,7 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                        if (!strcmp(argv[j], "--"))
                                seen_dashdash = j;
                if (seen_dashdash) {
+                       /* (2) */
                        if (seen_dashdash + 1 != argc - 1)
                                usage(blame_usage);
                        path = add_prefix(prefix, argv[seen_dashdash + 1]);
@@ -1769,6 +2209,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                }
                else {
                        /* (3) */
+                       if (argc <= i)
+                               usage(blame_usage);
                        path = add_prefix(prefix, argv[i]);
                        if (i + 1 == argc - 1) {
                                final_commit_name = argv[i + 1];
@@ -1793,17 +2235,19 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
        if (final_commit_name)
                argv[unk++] = final_commit_name;
 
-       /* Now we got rev and path.  We do not want the path pruning
+       /*
+        * Now we got rev and path.  We do not want the path pruning
         * but we may want "bottom" processing.
         */
        argv[unk++] = "--"; /* terminate the rev name */
        argv[unk] = NULL;
 
        init_revisions(&revs, NULL);
-       setup_revisions(unk, argv, &revs, "HEAD");
+       setup_revisions(unk, argv, &revs, NULL);
        memset(&sb, 0, sizeof(sb));
 
-       /* There must be one and only one positive commit in the
+       /*
+        * There must be one and only one positive commit in the
         * revs->pending array.
         */
        for (i = 0; i < revs.pending.nr; i++) {
@@ -1824,27 +2268,40 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
        }
 
        if (!sb.final) {
-               /* "--not A B -- path" without anything positive */
-               unsigned char head_sha1[20];
-
-               final_commit_name = "HEAD";
-               if (get_sha1(final_commit_name, head_sha1))
-                       die("No such ref: HEAD");
-               sb.final = lookup_commit_reference(head_sha1);
-               add_pending_object(&revs, &(sb.final->object), "HEAD");
+               /*
+                * "--not A B -- path" without anything positive;
+                * do not default to HEAD, but use the working tree
+                * or "--contents".
+                */
+               sb.final = fake_working_tree_commit(path, contents_from);
+               add_pending_object(&revs, &(sb.final->object), ":");
        }
+       else if (contents_from)
+               die("Cannot use --contents with final commit object name");
 
-       /* If we have bottom, this will mark the ancestors of the
+       /*
+        * If we have bottom, this will mark the ancestors of the
         * bottom commits we would reach while traversing as
         * uninteresting.
         */
        prepare_revision_walk(&revs);
 
-       o = get_origin(&sb, sb.final, path);
-       if (fill_blob_sha1(o))
-               die("no such path %s in %s", path, final_commit_name);
+       if (is_null_sha1(sb.final->object.sha1)) {
+               char *buf;
+               o = sb.final->util;
+               buf = xmalloc(o->file.size + 1);
+               memcpy(buf, o->file.ptr, o->file.size + 1);
+               sb.final_buf = buf;
+               sb.final_buf_size = o->file.size;
+       }
+       else {
+               o = get_origin(&sb, sb.final, path);
+               if (fill_blob_sha1(o))
+                       die("no such path %s in %s", path, final_commit_name);
 
-       sb.final_buf = read_sha1_file(o->blob_sha1, type, &sb.final_buf_size);
+               sb.final_buf = read_sha1_file(o->blob_sha1, &type,
+                                             &sb.final_buf_size);
+       }
        num_read_blob++;
        lno = prepare_lines(&sb);
 
@@ -1878,6 +2335,9 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 
        assign_blame(&sb, &revs, opt);
 
+       if (incremental)
+               return 0;
+
        coalesce(&sb);
 
        if (!(output_option & OUTPUT_PORCELAIN))
@@ -1891,7 +2351,7 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
                ent = e;
        }
 
-       if (DEBUG) {
+       if (show_stats) {
                printf("num read blob: %d\n", num_read_blob);
                printf("num get patch: %d\n", num_get_patch);
                printf("num commits: %d\n", num_commits);