Fix eatmydata env var setting

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/setting-tests-env-vars b/setting-tests-env-vars
index e89652d17b792807ed856f575539cbc056c34a49..19671ff091a90c7ab50fd24bb68d542933dc53b8 100755 (executable)
--- a/setting-tests-env-vars
+++ b/setting-tests-env-vars
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-${DGIT_TEST_RUN_PFX=eatmydata}
+: ${DGIT_TEST_RUN_PFX:=eatmydata}
 export DGIT_TEST_RUN_PFX
 
 export DGIT_TESTS_TMPDIR=/run/user/`id -u`/dgit-tests-tmp