Upgrade actions/checkout to v2

[S-S-X]

Fix #259

[github-actions]

Click for detailed source code test coverage report

Test coverage report for Technic CNC 87.33% in 11/14 files:

File                             Hits Missed Coverage
-----------------------------------------------------
programs.lua                   263  0      100.00%
materials/technic_worldgen.lua 32   0      100.00%
materials/init.lua             14   0      100.00%
materials/default.lua          183  0      100.00%
materials/basic_materials.lua  17   0      100.00%
init.lua                       16   0      100.00%
digilines.lua                  55   0      100.00%
cnc.lua                        53   0      100.00%
formspec.lua                   104  7      93.69%
api.lua                        217  43     83.46%
pipeworks.lua                  25   13     65.79%
materials/moreblocks.lua       0    29     0.00%
materials/ethereal.lua         0    37     0.00%
materials/bakedclay.lua        0    13     0.00%

Test coverage report for technic chests 45.56% in 6/6 files:

File          Hits Missed Coverage
----------------------------------
chests.lua    102  18     85.00%
init.lua      34   18     65.38%
register.lua  84   78     51.85%
formspec.lua  76   93     44.97%
inventory.lua 10   100    9.09%
digilines.lua 2    61     3.17%

Test coverage report for technic 60.74% in 95/95 files:

File                                      Hits Missed Coverage
--------------------------------------------------------------
max_lag.lua                               12   0      100.00%
machines/register/init.lua                15   0      100.00%
machines/register/freezer_recipes.lua     13   0      100.00%
machines/other/init.lua                   8    0      100.00%
machines/MV/solar_array.lua               12   0      100.00%
machines/MV/init.lua                      17   0      100.00%
machines/MV/grinder.lua                   17   0      100.00%
machines/MV/generator.lua                 9    0      100.00%
machines/MV/freezer.lua                   17   0      100.00%
machines/MV/extractor.lua                 17   0      100.00%
machines/MV/electric_furnace.lua          17   0      100.00%
machines/MV/compressor.lua                17   0      100.00%
machines/MV/centrifuge.lua                17   0      100.00%
machines/MV/cables.lua                    40   0      100.00%
machines/MV/battery_box.lua               17   0      100.00%
machines/MV/alloy_furnace.lua             19   0      100.00%
machines/LV/solar_array.lua               11   0      100.00%
machines/LV/init.lua                      17   0      100.00%
machines/LV/grinder.lua                   16   0      100.00%
machines/LV/generator.lua                 9    0      100.00%
machines/LV/electric_furnace.lua          15   0      100.00%
machines/LV/compressor.lua                20   0      100.00%
machines/LV/cables.lua                    40   0      100.00%
machines/LV/battery_box.lua               15   0      100.00%
machines/LV/alloy_furnace.lua             17   0      100.00%
machines/HV/solar_array.lua               11   0      100.00%
machines/HV/init.lua                      12   0      100.00%
machines/HV/grinder.lua                   17   0      100.00%
machines/HV/generator.lua                 9    0      100.00%
machines/HV/electric_furnace.lua          17   0      100.00%
machines/HV/compressor.lua                17   0      100.00%
machines/HV/cables.lua                    39   0      100.00%
machines/HV/battery_box.lua               17   0      100.00%
legacy.lua                                33   0      100.00%
items.lua                                 128  0      100.00%
crafts.lua                                133  0      100.00%
machines/LV/led.lua                       73   1      98.65%
config.lua                                51   1      98.08%
machines/register/compressor_recipes.lua  36   1      97.30%
machines/LV/geothermal.lua                75   3      96.15%
machines/register/cables.lua              96   4      96.00%
machines/register/solar_array.lua         46   2      95.83%
machines/LV/solar_panel.lua               42   2      95.45%
machines/network.lua                      397  22     94.75%
machines/register/alloy_recipes.lua       40   3      93.02%
tools/init.lua                            13   1      92.86%
machines/LV/water_mill.lua                67   6      91.78%
init.lua                                  20   2      90.91%
machines/register/grindings.lua           42   5      89.36%
machines/LV/lamp.lua                      110  14     88.71%
machines/register/grinder_recipes.lua     106  16     86.89%
util/throttle.lua                         9    2      81.82%
machines/register/machine_base.lua        165  41     80.10%
machines/LV/extractor.lua                 18   5      78.26%
machines/register/recipes.lua             62   20     75.61%
machines/register/battery_box.lua         223  72     75.59%
tools/flashlight.lua                      65   21     75.58%
machines/switching_station.lua            76   25     75.25%
machines/register/centrifuge_recipes.lua  21   7      75.00%
radiation.lua                             262  89     74.64%
effects.lua                               5    2      71.43%
machines/overload.lua                     12   5      70.59%
machines/MV/wind_mill.lua                 46   22     67.65%
machines/supply_converter.lua             95   46     67.38%
machines/other/coal_furnace.lua           2    1      66.67%
machines/other/injector.lua               72   39     64.86%
machines/switching_station_globalstep.lua 39   22     63.93%
machines/MV/hydro_turbine.lua             43   26     62.32%
machines/MV/tool_workshop.lua             56   34     62.22%
machines/register/generator.lua           122  88     58.10%
register.lua                              21   19     52.50%
tools/cans.lua                            53   48     52.48%
machines/power_monitor.lua                40   38     51.28%
machines/init.lua                         56   54     50.91%
machines/other/coal_alloy_furnace.lua     63   63     50.00%
machines/LV/music_player.lua              46   46     50.00%
tools/mining_lasers.lua                   39   40     49.37%
machines/other/constructor.lua            67   69     49.26%
tools/vacuum.lua                          19   21     47.50%
tools/tree_tap.lua                        24   27     47.06%
machines/HV/forcefield.lua                103  155    39.92%
machines/HV/nuclear_reactor.lua           119  205    36.73%
machines/register/common.lua              39   75     34.21%
machines/HV/quarry.lua                    122  245    33.24%
tools/chainsaw.lua                        40   83     32.52%
tools/multimeter.lua                      71   149    32.27%
machines/compat/api.lua                   16   34     32.00%
tools/sonic_screwdriver.lua               18   40     31.03%
machines/other/frames.lua                 184  445    29.25%
helpers.lua                               38   100    27.54%
tools/mining_drill.lua                    76   226    25.17%
machines/other/anchor.lua                 14   74     15.91%
machines/compat/digtron.lua               2    11     15.38%
tools/prospector.lua                      16   92     14.81%
machines/register/extractor_recipes.lua   6    65     8.45%

Raw test runner output for geeks:

CNC:

●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●
31 successes / 0 failures / 0 errors / 0 pending : 0.429953 seconds

Chests:

W:	Configuration: invalid key	exclude_textures
W:	Configuration: invalid key	validate_textures
●●●●●
5 successes / 0 failures / 0 errors / 0 pending : 0.031482 seconds

Technic:

●◌◌●●●◌●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●◌●●●●●
176 successes / 0 failures / 0 errors / 4 pending : 6.365818 seconds

Pending → spec/api_spec.lua @ 133
Technic API Machine registration registers my_mod:my_battery
spec/api_spec.lua:133: Battery box registration does not include all fields

Pending → spec/api_spec.lua @ 190
Technic API Machine registration registers my_mod:machine_base
spec/api_spec.lua:190: Base machine registration does not include all fields

Pending → spec/api_spec.lua @ 285
Technic API internals technic.cables TBD, misleading name and should be updated
spec/api_spec.lua:285: TBD technic.cables naming and need, see technic networks data for possible options

Pending → spec/supply_converter_spec.lua @ 78
Supply converter building overloads network
spec/supply_converter_spec.lua:78: overload does not work with supply converter

[S-S-X]

@v2 upgrade is not really needed as submodules are not actually used by actions/checkout, that was just me getting distracted. it is however better as submodules and git over ssh works correctly with v2. @v2 gets ping because of.

[BuckarooBanzay]

ah yes, the submodule thing :/