tests: fix bashism to load helpers.sh
`source` isn't available at POSIX sh.
% create subversion repo
Checked out revision 0.
A src
A src/alpha
A externals
A externals/other
Adding externals
Adding externals/other
Adding src
Adding src/alpha
Transmitting file data ..
Committed revision 1.
At revision 1.
property 'svn:externals' set on 'src'
Sending src
Committed revision 2.
% create hg repo
% first revision, no sub
adding a
% add first svn sub with leading whitespaces
committing subrepository s
% debugsub
path s
source file:///root/svn-repo/src
revision 2
% change file in svn and hg, commit
committing subrepository s
Sending s/alpha
Transmitting file data .
Committed revision 3.
Fetching external item into 's/externals'
External at revision 1.
At revision 3.
path s
source file:///root/svn-repo/src
revision 3
% should be empty despite change to s/a
% add a commit from svn
U alpha
Fetching external item into 'externals'
A externals/other
Updated external to revision 1.
Updated to revision 3.
property 'svn:mime-type' set on 'alpha'
Sending src/alpha
Transmitting file data .
Committed revision 4.
% this commit from hg will fail
committing subrepository s
abort: svn: Commit failed (details follow):
svn: File '/src/alpha' is out of date
% this commit fails because of meta changes
property 'svn:mime-type' set on 's/alpha'
committing subrepository s
abort: svn: Commit failed (details follow):
svn: File '/src/alpha' is out of date
% this commit fails because of externals changes
committing subrepository s
abort: cannot commit svn externals
% this commit fails because of externals meta changes
property 'svn:mime-type' set on 's/externals/other'
committing subrepository s
abort: cannot commit svn externals
% clone
updating to branch default
A tc/s/alpha
U tc/s
Fetching external item into 'tc/s/externals'
A tc/s/externals/other
Checked out external at revision 1.
Checked out revision 3.
3 files updated, 0 files merged, 0 files removed, 0 files unresolved
% debugsub in clone
path s
source file:///root/svn-repo/src
revision 3
% verify subrepo is contained within the repo directory
True