Fix tests with latest go cmp

[dnephin]

Fixes #155

[thaJeztah]

Looks like tests are failing (on older Go versions?) @dnephin
Wondering if those versions should still be tested though, because Go 1.10 and older reached EOL

[dnephin]

Ya, I'd like to find a way to test it that works with all versions

[anthonyfok]

I ran into this test error randomly, even with the PR patch applied:

=== RUN   TestDeepEqual
--- FAIL: TestDeepEqual (0.00s)
    compare_test.go:20: expected 
        "\n--- result\n+++ exp\n  []string{\n- \t\"a\",\n+ \t\"b\",\n- \t\"b\",\n+ \t\"a\",\n  }\n"
        got
        "\n--- result\n+++ exp\n\u00a0\u00a0[]string{\n-\u00a0\t\"a\",\n+\u00a0\t\"b\",\n-\u00a0\t\"b\",\n+\u00a0\t\"a\",\n\u00a0\u00a0}\n"

It turns out that go-cmp 0.3.0, the report randomly chooses between normal space (0x20) and non-breaking space (0xa0) in the report... I just got bitten by this in Debian packaging, as one build succeeds and yet the next build fails even though I did not change anything.

See google/go-cmp#124 for the whole story.

[codecov]

Codecov Report

Merging #158 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #158   +/-   ##
=======================================
  Coverage   83.16%   83.16%           
=======================================
  Files          29       29           
  Lines        2038     2038           
=======================================
  Hits         1695     1695           
  Misses        236      236           
  Partials      107      107

Impacted Files	Coverage Δ
internal/source/source.go	73.25% <100%> (ø)	⬆️

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[dnephin]

Alright, tests seem to be passing now