[Chicken-janitors] #1455: XDG basedir support for csi config, egg cache and maybe more

[Chicken Trac]

#1455: XDG basedir support for csi config, egg cache and maybe more
----------------------------+--------------------------------
 Reporter:  wasamasa        |                 Owner:
     Type:  change request  |                Status:  new
 Priority:  minor           |             Milestone:  someday
Component:  core tools      |               Version:  5.0
 Keywords:                  |  Estimated difficulty:  easy
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 https://specifications.freedesktop.org/basedir-spec/basedir-spec-
 latest.html
 https://blogs.msdn.microsoft.com/oldnewthing/20050701-09/?p=35133/
 https://msdn.microsoft.com/en-
 us/library/windows/desktop/dd378457(v=vs.85).aspx

 This is a specification that allows users to unclutter their home
 directory by keeping config files in (a customizable) directory and cache
 files in another one (also customizable).  An example implementation for
 Unix-likes (where it's safe to assume `HOME` is set) has been attached.
 Windows has something (almost) comparable in form of the `APPDATA` (for
 user-specific configuration) and `LOCALAPPDATA` (for user-specific non-
 configuration, exists since Vista) environment variables.  In case
 `LOCALAPPDATA` isn't defined, `APPDATA` could be used instead.  I'm not
 100% sure whether you can just use `get-environment-variable` on Windows
 and have it work, someone would need to test this.

 With this we could (for both Windows and Unix-likes):

 - Look up a user config/cache directory for the platform
 - Check whether a config/cache file exists
 - If yes, read it from that location, otherwise fall back to a default

 The last one is optional and might make this a change request. Falling
 back to a default would preserve default behavior, ignoring it would
 introduce a change.  Possible candidates include `~/.csirc` (config), the
 egg cache (cache) and setup-defaults (config).

 PS: Looking up `.csirc` on Windows probably never worked as it relies on
 resolving `HOME` which isn't set by default.  This would make it work
 again, albeit for a different location than previously documented.

--
Ticket URL: <https://bugs.call-cc.org/ticket/1455>
CHICKEN Scheme <https://www.call-cc.org/>
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