Added branch load counter to fast-import.

If the branch load count exceeds the number of branches created then
the frontend is causing fast-import to page branches into and out of
memory due to the way its ordering its commits.  Performance can
likely be increased if the frontend were to alter its commit
sequence such that it stays on one branch before switching to another
branch, then never returns to the prior branch.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

fast-import.c

@@ -190,6 +190,7 @@ struct branch
 static unsigned long max_depth = 10;
 static unsigned long alloc_count;
 static unsigned long branch_count;
+static unsigned long branch_load_count;
 static unsigned long object_count;
 static unsigned long duplicate_count;
 static unsigned long marks_set_count;
@@ -1059,6 +1060,7 @@ static void load_branch(struct branch *b)
 	b->active_next_branch = active_branches;
 	active_branches = b;
 	cur_active_branches++;
+	branch_load_count++;
 }
 
 static void file_change_m(struct branch *b)
@@ -1382,9 +1384,9 @@ int main(int argc, const char **argv)
 	fprintf(stderr, "      trees  :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TREE], duplicate_count_by_type[OBJ_TREE]);
 	fprintf(stderr, "      commits:   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_COMMIT], duplicate_count_by_type[OBJ_COMMIT]);
 	fprintf(stderr, "      tags   :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TAG], duplicate_count_by_type[OBJ_TAG]);
-	fprintf(stderr, "Total branches:  %10lu\n", branch_count);
-	fprintf(stderr, "      atoms:     %10u\n", atom_cnt);
+	fprintf(stderr, "Total branches:  %10lu (%10lu loads     )\n", branch_count, branch_load_count);
 	fprintf(stderr, "      marks:     %10u (%10lu unique    )\n", (1 << marks->shift) * 1024, marks_set_count);
+	fprintf(stderr, "      atoms:     %10u\n", atom_cnt);
 	fprintf(stderr, "Memory total:    %10lu KiB\n", (total_allocd + alloc_count*sizeof(struct object_entry))/1024);
 	fprintf(stderr, "       pools:    %10lu KiB\n", total_allocd/1024);
 	fprintf(stderr, "     objects:    %10lu KiB\n", (alloc_count*sizeof(struct object_entry))/1024);