Make test-bundle-type work on MacOS 10.4.11

head on MacOS Tiger doesn't have a -c option.

tests/test-bundle-type

@@ -20,7 +20,7 b' for t in "None" "bzip2" "gzip"; do'
   hg init t$t
   cd t1
   hg bundle -t $t ../b$t ../t$t
-  head -c 6 ../b$t
+  head -n 1 ../b$t | cut -b 1-6
   cd ../t$t
   hg pull ../b$t
   hg up

tests/test-bundle-type.out

@@ -15,7 +15,8 b' summary: a'
 % test bundle type None
 searching for changes
 1 changesets found
-HG10UNpulling from ../bNone
+HG10UN
+pulling from ../bNone
 requesting all changes
 adding changesets
 adding manifests
@@ -27,7 +28,8 b' summary: a'
 % test bundle type bzip2
 searching for changes
 1 changesets found
-HG10BZpulling from ../bbzip2
+HG10BZ
+pulling from ../bbzip2
 requesting all changes
 adding changesets
 adding manifests
@@ -39,7 +41,8 b' summary: a'
 % test bundle type gzip
 searching for changes
 1 changesets found
-HG10GZpulling from ../bgzip
+HG10GZ
+pulling from ../bgzip
 requesting all changes
 adding changesets
 adding manifests