Add build stage for documentation

[odow]

This PR adds a documentation build stage to Travis, following these instructions:
https://discourse.julialang.org/t/psa-use-a-project-for-building-your-docs/14974

Let's see what happens.

[codecov]

Codecov Report

Merging #1485 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1485   +/-   ##
=======================================
  Coverage   88.83%   88.83%           
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  Files          27       27           
  Lines        3655     3655           
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  Hits         3247     3247           
  Misses        408      408

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[codecov]

Codecov Report

Merging #1485 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1485   +/-   ##
=======================================
  Coverage   88.83%   88.83%           
=======================================
  Files          27       27           
  Lines        3655     3655           
=======================================
  Hits         3247     3247           
  Misses        408      408

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d2717b0...ae16e3d. Read the comment docs.

[odow]

@fredrikekre what did I do wrong?

I just followed the Colors.jl example:
https://github.com/JuliaGraphics/Colors.jl/blob/master/docs/Project.toml
https://github.com/JuliaGraphics/Colors.jl/blob/master/.travis.yml

[fredrikekre]

You need

# Workaround for JuliaLang/julia/pull/28625
if Base.HOME_PROJECT[] !== nothing
    Base.HOME_PROJECT[] = abspath(Base.HOME_PROJECT[])
end

at the top of docs/make.jl, see Gotcha 2 I added to the top post of https://discourse.julialang.org/t/psa-use-a-project-for-building-your-docs/14974

[odow]

Oops, sorry, I should have tried that first. It might be worth editing the discourse post because the word "might" put me off, and I had a quick look at the Julia issue and it didn't seem relevant.

Maybe say:

If you encounter an error like

ERROR: LoadError: ArgumentError: Package XXX not found in current path:
- Run `Pkg.add("XXX")` to install the XXX package.

you've run into JuliaLang/julia#28625 which is a bug in Julia ...

[fredrikekre]

Yea, updated. It is actually if you have doctests that you get that without the workaround.

[odow]

Great, thanks for your help!