add istext -> istextmime

[stevengj]

Compatibility for JuliaLang/julia#15708

[stevengj]

I originally had if VERSION < v"0.5.0-dev+10878", which the version.sh script tells me is the correct version for the merge commit JuliaLang/julia@839f8c9 for JuliaLang/julia#15708, but the nightly build on Travis and AppVeyor still gave me a failure, claiming I was exporting istextmime when it was already defined by Base. So, I just switched it to if !isdefined(Base, :istextmime)

[tkelman]

10000 sounds way too high, should be more like 3-4000. Something went wrong there.

[martinholters]

I get 0.5.0-dev+3460 for that commit which sounds reasonable. But the !defined check works too, obviously.

[tkelman]

@vtjnash mentioned somewhere having experienced "resistance" to basing things on isdefined instead of version numbers. How long ago was this and in what context, if you can remember? I think feature-checks are generally preferable to using version numbers.

[stevengj]

I think the advantage of version checks is that it is obvious when they can be removed. e.g. if I see a VERSION < v"0.2-xxx" in my code, but I require Julia 0.4, then I can obviously remove the check. If I have isdefined(Base, :frob), figuring out whether it is safe to remove may involve digging through the Julia logs.

[stevengj]

I just tried on another computer, and I get 0.5.0-dev+10878 from the Compat.jl version.sh script.

[stevengj]

Oh, I see the problem. I need to do git pull --tags. I hate git sometimes...why doesn't it pull all the tags on the current branch by default?