tests: Avoid use of user's GPG keys during tests

The TestPullAdd test uses git CLI to perform a commit.
Contributors with signing enabled globally would have their GPG
configuration being used to sign that test commit.

This behaviour was transparent for contributors that do not use
secure keys which requires physical confirmation.
The new behaviour disables GPG signing for that test, which was
not required as part of the test.

Signed-off-by: Paulo Gomes <pjbgf@linux.com>

worktree_test.go

@@ -259,7 +259,7 @@ func (s *RepositorySuite) TestPullAdd(c *C) {
 	ExecuteOnPath(c, path,
 		"touch foo",
 		"git add foo",
-		"git commit -m foo foo",
+		"git commit --no-gpg-sign -m foo foo",
 	)
 
 	w, err := r.Worktree()