diff-tree: teach single-commit diff-tree to honour grafts

We used to read the commit objects by hand and ignored the grafts.
Rewrite it using lookup_commit() API, to make it grafts-aware.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/diff-tree.c b/diff-tree.c
index da9c68c..d56d921 100644 (file)
--- a/diff-tree.c
+++ b/diff-tree.c
@@ -69,52 +69,50 @@ static int diff_root_tree(const unsigned char *new, const char *base)
        return retval;
 }
 
-static const char *generate_header(const char *commit, const char *parent, const char *msg, unsigned long len)
+static const char *generate_header(const char *commit, const char *parent, const char *msg)
 {
        static char this_header[16384];
        int offset;
+       unsigned long len;
 
        if (!verbose_header)
                return commit;
 
+       len = strlen(msg);
        offset = sprintf(this_header, "%s%s (from %s)\n", header_prefix, commit, parent);
        offset += pretty_print_commit(commit_format, msg, len, this_header + offset, sizeof(this_header) - offset);
        return this_header;
 }
 
-static int diff_tree_commit(const unsigned char *commit, const char *name)
+static int diff_tree_commit(const unsigned char *commit_sha1)
 {
-       unsigned long size, offset;
-       char *buf = read_object_with_reference(commit, "commit", &size, NULL);
+       struct commit *commit;
+       struct commit_list *parents;
+       char name[50];
+       unsigned char sha1[20];
 
-       if (!buf)
+       sprintf(name, "%s^0", sha1_to_hex(commit_sha1));
+       if (get_sha1(name, sha1))
                return -1;
-
-       if (!name) {
-               static char commit_name[60];
-               strcpy(commit_name, sha1_to_hex(commit));
-               name = commit_name;
-       }
-
+       name[40] = 0;
+       commit = lookup_commit(sha1);
+       
        /* Root commit? */
-       if (show_root_diff && memcmp(buf + 46, "parent ", 7)) {
-               header = generate_header(name, "root", buf, size);
-               diff_root_tree(commit, "");
+       if (show_root_diff && !commit->parents) {
+               header = generate_header(name, "root", commit->buffer);
+               diff_root_tree(commit_sha1, "");
        }
 
        /* More than one parent? */
-       if (ignore_merges) {
-               if (!memcmp(buf + 46 + 48, "parent ", 7))
+       if (ignore_merges && commit->parents && commit->parents->next)
                        return 0;
-       }
 
-       offset = 46;
-       while (offset + 48 < size && !memcmp(buf + offset, "parent ", 7)) {
-               unsigned char parent[20];
-               if (get_sha1_hex(buf + offset + 7, parent))
-                       return -1;
-               header = generate_header(name, sha1_to_hex(parent), buf, size);
-               diff_tree_sha1_top(parent, commit, "");
+       for (parents = commit->parents; parents; parents = parents->next) {
+               struct commit *parent = parents->item;
+               header = generate_header(name,
+                                        sha1_to_hex(parent->object.sha1),
+                                        commit->buffer);
+               diff_tree_sha1_top(parent->object.sha1, commit_sha1, "");
                if (!header && verbose_header) {
                        header_prefix = "\ndiff-tree ";
                        /*
@@ -122,9 +120,7 @@ static int diff_tree_commit(const unsigned char *commit, const char *name)
                         * don't print the diffs.
                         */
                }
-               offset += 48;
        }
-       free(buf);
        return 0;
 }
 
@@ -147,7 +143,7 @@ static int diff_tree_stdin(char *line)
                return diff_tree_sha1_top(parent, commit, "");
        }
        line[40] = 0;
-       return diff_tree_commit(commit, line);
+       return diff_tree_commit(commit);
 }
 
 static const char diff_tree_usage[] =
@@ -250,7 +246,7 @@ int main(int argc, const char **argv)
                        usage(diff_tree_usage);
                break;
        case 1:
-               diff_tree_commit(sha1[0], NULL);
+               diff_tree_commit(sha1[0]);
                break;
        case 2:
                diff_tree_sha1_top(sha1[0], sha1[1], "");