git-branch: default to --track

"git branch --track" will setup config variables when branching from
a remote branch, so that if you say "git pull" while being on that
branch, it automatically fetches the correct remote, and merges the
correct branch.

Often people complain that this is not the default for "git branch".
Make it so.
Signed-off-by: NJohannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-branch.c

@@ -22,7 +22,7 @@ static const char builtin_branch_usage[] =
 static const char *head;
 static unsigned char head_sha1[20];
 
-static int branch_track_remotes;
+static int branch_track_remotes = 1;
 
 static int branch_use_color;
 static char branch_colors[][COLOR_MAXLEN] = {