tests/test-patch.out

tests: fix bashism to load helpers.sh

`source` isn't available at POSIX sh.

adding a
% check custom patch options are honored
requesting all changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
applying ../a.diff
Using custom patch