CI does set it for us, but we don't allow env vars through to the test
scripts by default. Linux's default for XDG_CONFIG_DIR will be within
the temporary $HOME, so put the Windows one there as well.
The F-Droid index format contains absolute download urls, so setting up
a custom config for the tests with the original index file won't work
when dowlnoading APKs. Those will still get downloaded from f-droid.org.
To fix that, use http.Client.Transport instead of a custom config. This
requires less code, introduces less test code in non-test files, and
means we can use the default config in the tests.
This has multiple advantages. For one, we can simplify our code, as we
can use globals like os.Stdout and flagsets directly.
It will also be easier to write parallel tests which will run faster, as
each testscript runs concurrently.
While at it, start using $HOME if set, as that is often better than
blindly relying on the current user's home directory via cgo.
Go 1.11 and 1.12 add os.UserCacheDir and os.UserHomeDir respectively, so
soon enough we'll be able to replace most of basedir with those.
Finally, stop having the tests require on the f-droid.org repository to
work. Committing under 2MB of data is plenty to get the files we need in
a static local http server, which makes the tests much faster and not
depend on an internet connection.
Follow-up commits will finish porting the rest of the tests.
Linus789
Daniel Martí