Avoid error on stderr with older git
commit272430a170a49cfa7e3400e1dbaddc2f6e97f495
authorOlly Betts <olly@survex.com>
Sun, 30 Sep 2018 22:37:53 +0000 (1 11:37 +1300)
committerOlly Betts <olly@survex.com>
Wed, 3 Oct 2018 04:35:52 +0000 (3 17:35 +1300)
treeeca8788482477c74250bfdac05b2c213870af3f2
parentff8a2ae2226e4dcd4936d99123b1a76ce988c6c8
Avoid error on stderr with older git

Discard stderr when trying to use git worktree, which is a fairly recent
addition.

(cherry picked from commit c6e458380e674adaabb61ef3b2ae5c2c3aca16f4)
bootstrap