t/test-lib: introduce OID_REGEX

Currently we have a variable, $_x40, which contains a regex that matches
a full 40-character hex constant.  However, with NewHash, we'll have
object IDs that are longer than 40 characters.  In such a case, $_x40
will be a confusing name.  Create a $OID_REGEX variable which will
always reflect a regex matching the appropriate object ID, regardless of
the length of the current hash.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/test-lib.sh

@@ -184,6 +184,7 @@ _x40="$_x35$_x05"
 # Zero SHA-1
 _z40=0000000000000000000000000000000000000000
 
+OID_REGEX="$_x40"
 ZERO_OID=$_z40
 EMPTY_TREE=4b825dc642cb6eb9a060e54bf8d69288fbee4904
 EMPTY_BLOB=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
@@ -196,7 +197,7 @@ LF='
 # when case-folding filenames
 u200c=$(printf '\342\200\214')
 
-export _x05 _x35 _x40 _z40 LF u200c EMPTY_TREE EMPTY_BLOB ZERO_OID
+export _x05 _x35 _x40 _z40 LF u200c EMPTY_TREE EMPTY_BLOB ZERO_OID OID_REGEX
 
 # Each test should start with something like this, after copyright notices:
 #