Switch CI to use GitHub Actions

[fingolfin]

This is necessary as Travis CI started to require payment for its services.

[codecov[bot]]

Codecov Report

Merging #20 (140c8eb) into master (2bfd41d) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #20   +/-   ##
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  Coverage   97.59%   97.59%           
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  Files          14       14           
  Lines        2040     2040           
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  Hits         1991     1991           
  Misses         49       49           

[fingolfin]

@egri-nagy the tests in wreath.tst for GroupWreathProduct fail in GAP 4.11 and GAP master. Indeed:

gap> A:=Z2;; B:=Z2;; C:=Z3;;
gap> AB := Image(IsomorphismPermGroup(GroupWreathProduct([A,B])));;
gap> BC := Image(IsomorphismPermGroup(GroupWreathProduct([B,C])));;
gap> ABC := Image(IsomorphismPermGroup(GroupWreathProduct([A,B,C])));
<permutation group of size 648 with 3 generators>
gap> AB_C := Image(IsomorphismPermGroup(GroupWreathProduct([AB,C])));
<permutation group of size 52488 with 3 generators>
gap> A_BC := Image(IsomorphismPermGroup(GroupWreathProduct([A,BC])));
<permutation group of size 648 with 3 generators>

Any idea ?

[fingolfin]

Ah I now see this is in issue #19.

we could run git bisect on GAP to figure out which on caused it to regress. That might at least give a hint.

[egri-nagy]

Thank you for the GitHub Actions migrations. I was not up-to-date with the Travis CI's new business model.

As for the problem with the GroupWreathProduct, I'll have a closer look.I hope it will not get to bisecting. :)