[gitg] Respect the mainline of the merges

[Ignacio Casal Quinteiro <icq src gnome org>]

commit d3cb803007aa5e36de8fe6442a202d5142514091
Author: Techlive Zheng <techlivezheng gmail com>
Date:   Thu May 16 18:35:53 2013 +0800

    Respect the mainline of the merges
    
    Normally the 1st parent of a commit is the branch we're merging _into_,
    so if you keep this on the left then you can always read a merge as
    right-to-left. Previous it seems to be a bit random.
    
    By comparing the position a 'lane' in the 'lanes', the earier a lane is
    created, the more priority it has.
    
    Signed-off-by: Ignacio Casal Quinteiro <icq gnome org>

 libgitg/gitg-lanes.vala |   29 +++++++++++++++++++++--------
 1 files changed, 21 insertions(+), 8 deletions(-)
---
diff --git a/libgitg/gitg-lanes.vala b/libgitg/gitg-lanes.vala
index da725ad..b96acd0 100644
--- a/libgitg/gitg-lanes.vala
+++ b/libgitg/gitg-lanes.vala
@@ -157,14 +157,27 @@ public class Lanes : Object
                        if (container != null)
                        {
                                // there is already a lane for this parent. This means that
-                               // we add pos as a merge for the lane, also this means the
-                               // color of this lane incluis the merge should change to
-                               // one color
-                               container.lane.from.append(pos);
-                               container.lane.color.next_index();
-
-                               container.inactive = 0;
-                               container.from = myoid;
+                               // we add pos as a merge for the lane.
+                               if (i == 0 && pos < lnpos)
+                               {
+                                       // we are at the mainline of a merge, and this parent has
+                                       // already been assigned to an existing lane, if our
+                                       // lane's pos is smaller, then the this parent should be in
+                                       // our lane instead.
+                                       mylane.to = poid;
+                                       mylane.from = myoid;
+                                       mylane.lane.from.append(lnpos);
+                                       mylane.lane.color = Color.next();
+                                       mylane.inactive = 0;
+                                       d_lanes.remove(container);
+                               }
+                               else
+                               {
+                                       container.from = myoid;
+                                       container.lane.from.append(pos);
+                                       container.lane.color.next_index();
+                                       container.inactive = 0;
+                               }
 
                                continue;
                        }