graph API: use a new color when starting a brand new column

Use a new color for commits that don't have any previously printed
children.  The following command demonstrates the changes:

  git log --graph --pretty=tformat:'%h %s%n' -7 481c7a6 18b0793

Now the two independent lines of development are displayed with
different colors, instead of both using the same color.

Signed-off-by: Adam Simpkins <simpkins@facebook.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/graph.c b/graph.c
index e466770208d73d8e1f5bc7f6b12728b6f2b7c6bb..f3226ec94a5b59372096698e216af60169d565f6 100644 (file)
--- a/graph.c
+++ b/graph.c
@@ -225,7 +225,12 @@ struct git_graph *graph_init(struct rev_info *opt)
        graph->num_columns = 0;
        graph->num_new_columns = 0;
        graph->mapping_size = 0;
-       graph->default_column_color = 0;
+       /*
+        * Start the column color at the maximum value, since we'll
+        * always increment it for the first commit we output.
+        * This way we start at 0 for the first commit.
+        */
+       graph->default_column_color = COLUMN_COLORS_MAX - 1;
 
        /*
         * Allocate a reasonably large default number of columns
@@ -499,11 +504,14 @@ static void graph_update_columns(struct git_graph *graph)
                             parent;
                             parent = next_interesting_parent(graph, parent)) {
                                /*
-                                * If this is a merge increment the current
+                                * If this is a merge, or the start of a new
+                                * childless column, increment the current
                                 * color.
                                 */
-                               if (graph->num_parents > 1)
+                               if (graph->num_parents > 1 ||
+                                   !is_commit_in_columns) {
                                        graph_increment_column_color(graph);
+                               }
                                graph_insert_into_new_columns(graph,
                                                              parent->item,
                                                              &mapping_idx);