[root@repos ~]# salt model file.append /tmp/test "test:test"
model:
    Wrote 1 lines to "/tmp/test"
[root@repos ~]# salt model cmd.run "cat /tmp/test"
model:
    test:test
[root@repos ~]# salt model file.append /tmp/test "test: test"
model:
    Wrote 1 lines to "/tmp/test"
[root@repos ~]# salt model cmd.run "cat /tmp/test"
model:
    test:test
    {'test': 'test'}
[root@repos ~]# salt model file.append /tmp/test "test: test: test: test"
model:
    Wrote 1 lines to "/tmp/test"
[root@repos ~]# salt model cmd.run "cat /tmp/test"
model:
    test:test
    {'test': 'test'}
    test: test: test: test
[root@repos ~]# salt model file.append /tmp/test "test: test:test:test"
model:
    Wrote 1 lines to "/tmp/test"
[root@repos ~]# salt model cmd.run "cat /tmp/test"
model:
    test:test
    {'test': 'test'}
    test: test: test: test
    {'test': 'test:test:test'}
[root@repos ~]# salt model file.append /tmp/test "test: test:test: test"
model:
    Wrote 1 lines to "/tmp/test"
[root@repos ~]# salt model cmd.run "cat /tmp/test"
model:
    test:test
    {'test': 'test'}
    test: test: test: test
    {'test': 'test:test:test'}
    test: test:test: test
[root@repos ~]# salt --version
salt 0.15.3