Make .crystal directory location configurable

[jhass]

• Default behaviour unchanged
• Allows to not clutter stuff up with .crystal directories wherever you happen to run crystal eval
• No conflicts, generated files are already namespaced by their full path
• Potential reusage of temporary files after changing the current working directory and compiling the same file again
• Slight speedup by setting the location to somewhere in /tmp
• If we later decide to put the default location into /tmp/crystal, ~/.crystal or whatever, if available, there's now a central place to implement that logic.

[bararchy]

Yes !!! Yes please , I have like 10 different hidden .crystal folder all over my /home .
Thanks @jhass
+5 for this

[vyp]

+1 of course, but I don't think it should clutter the home directory unless it's a hidden folder. So not ~/crystal, but maybe ~/.crystal or ~/.cache/crystal or something.

[vyp]

Not that this pr does that of course, just referring to your last bullet point.

[asterite]

Looks good. Should it be named CRYSTAL_TMP_DIR maybe?

[jhass]

Don't care much about the name, just used what was used in the codebase already. Should I change it?

[asterite]

I wouldn't care about the name either, except that it has to be set as an ENV var. I think CRYSTAL_TMP_DIR is better, CRYSTAL_OUTPUT_DIR sounds like the dir where executables are going to be created.

[jhass]

Changed to CRYSTAL_CACHE_DIR after discussion on IRC.

[ysbaddaden]

👍 that would help with my ecryptfs home, where I sometimes hit the filename length limit.

[bcardiff]

👍 I was thinking to anchor .crystal to be a sibling of the Projectfile. But fixing to the whole environment seems simpler.