[PATCH] contrib/subtree - unset prefix before proceeding

This is to prevent unwanted prefix when such an environment variable
exists. The case occurs for example during the Debian package build
where the git-subtree test suite is called with 'prefix=/usr', which
makes test 21 fail:
not ok 21 - Check that prefix argument is required for split

Signed-off-by: Gilles Filippini <redacted>
---
 contrib/subtree/git-subtree.sh | 1 +
 1 file changed, 1 insertion(+)

diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index dc59a91..db925ca 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh

@@ -46,6 +46,7 @@ ignore_joins=
 annotate=
 squash=
 message=
+prefix=
 
 debug()
 {

-- 
1.9.0