According to the NO_COLOR FAQ, "user-level configuration files [...] should
override $NO_COLOR." https://no-color.org/
Unfortunately this makes it harder to test the $NO_COLOR behavior since the
test environment isn't attached to a tty. We could allocate a pty or
LD_PRELOAD shim to intercept isatty(), but I feel it would be too much to do.
https://github.com/assert-rs/assert_cmd/issues/138
With this patch, the order is this:
`$JJ_EDITOR` environement variable
`ui.editor` config
`$VISUAL` environement variable
`$EDITOR` environement variable
`pico`
That matches git, except that git falls back to an editor determined
at compile time (usually `vi`) instead of using `pico`.
As I said in 095fb9fef4, removing support for `~/.jjconfig` was an
experiment. I've heard from a few people (including in #233) that they
would prefer to have configs in the home directory. This patch
therefore restores that functionality, except I added a `.toml`
extension to the file to clarify the expected format to users and
editors.
After this patch, we still allow configs in `$XDG_CONFIG_HOME` (and
the other paths used by `dirs::config_dir()`), but we error out there
are config files in both that location and `~/.jjconfig.toml`.
