Here is the detailed output:

network/issue2545_command-execution-via-ssh-uri.sh (Darcs1)
(PatienceDiff): [Failed]
| . sshlib                        # Load ssh helpers.
| + . sshlib
| if [ x${REMOTE_DIR} = x ]; then
|   REMOTE_DIR=/tmp/darcs-ssh-test
| fi
| ++ '[' x = x ']'
| ++ REMOTE_DIR=/tmp/darcs-ssh-test
| 
| if [ x"${USE_PUTTY}" != x ]; then
|   DARCS_SSH=plink
|   export DARCS_SSH
|   DARCS_SCP=pscp
|   export DARCS_SCP
|   DARCS_SFTP=psftp
|   export DARCS_SFTP
| fi
| ++ '[' x '!=' x ']'
| 
| if [ x"${USE_CONTROL_MASTER}" != x ]; then
|   DARCS_SSH_FLAGS="--ssh-cm"
|   export DARCS_SSH_FLAGS
| fi
| ++ '[' x '!=' x ']'
| 
| if [ x"${DARCS_SSH}" = x ]; then
|   SSH=ssh
| else
|   SSH=${DARCS_SSH}
| fi
| ++ '[' x = x ']'
| ++ SSH=ssh
| 
| if [ x${REMOTE} = x ]; then
|   REMOTE=$(whoami)@localhost
| fi
| ++ '[' x = x ']'
| whoami
| +++ whoami
| ++ REMOTE=ben@localhost
| 
| init_remote_repo() {
|     repodir="${1:-R}"
| 
|     ${SSH} ${REMOTE} \
|         "rm -rf '${REMOTE_DIR}' && mkdir '${REMOTE_DIR}' && \
|             cd '${REMOTE_DIR}' && darcs init --repo '$repodir'"
| }
| 
| # test if we can connect via ssh, otherwise skip test
| ${SSH} -x -o=NumberofPasswordPrompts=0 ${REMOTE} true || exit 200
| ++ ssh -x -o=NumberofPasswordPrompts=0 ben@localhost true
| 
| # vim: syntax=sh:
| 
| init_remote_repo R              # Create our test repos.
| + init_remote_repo R
| + repodir=R
| + ssh ben@localhost 'rm -rf '\''/tmp/darcs-ssh-test'\'' && mkdir
'\''/tmp/darcs-ssh-test'\'' &&             cd
'\''/tmp/darcs-ssh-test'\'' && darcs init --repo '\''R'\'''
| darcs init      --repo R        #
| + darcs init --repo R
| cd R
| + cd R
| 
| echo "text" > file              # Modify the working dir
| + echo text
| darcs record -lam "First Patch" # Record the changes
| + darcs record -lam 'First Patch'
| 
| check="\"${SSH}\" \"--\" \"${REMOTE}\" \"darcs apply --all --debug
--repodir '${REMOTE_DIR}/R'\""
| + check='"ssh" "--" "ben@localhost" "darcs apply --all --debug
--repodir '\''/tmp/darcs-ssh-test/R'\''"'
| darcs push -a --debug "${REMOTE}":"${REMOTE_DIR}"/R 2>&1 >/dev/null | \
|     grep -F "$check"
| + darcs push -a --debug ben@localhost:/tmp/darcs-ssh-test/R
| + grep -F '"ssh" "--" "ben@localhost" "darcs apply --all --debug
--repodir '\''/tmp/darcs-ssh-test/R'\''"'

Ok, this is not a regression but a problem in the test script or rather
in the tests/network/sshlib's function init_remote_repo: it creates a
darcs repo remotely via ssh which means that our test-local
.darcs/config is not in effect. This causes the remote repo to be a
darcs-2 repo even if we test for darcs-1, since the mechanism we select
darcs1/darcs2 is via the defaults file.

resolved by

patch f4352f14ac8eb6ee3f171def4c07541e28fd93dd
Author: Ben Franksen <benjamin.franksen@helmholtz-berlin.de>
Date:   Thu Feb 22 19:10:42 CET 2018
  * resolve issue2563: create remote repo in correct format in ssh 
tests