* Fix unused variables
* Don't read git files when --no-gitconfig is given
Despite starting delta with `--no-gitconfig`, strace still shows
that `.git/config` etc. files are accessed. By no longer doing
that it is very clear that no config options are read from there.
`env::set_var` is not-yet-unsafe, and here tests fail
because a var is already set by a second test while the first one
is still running.
`cargo test -- test_env` with sufficient (auto detected) parallelism
triggers this.
This allow to no longer ignore some tests (marked previously as FIXME)
by storing the env at the start of the program (Or creating a custom env
for test purpose)
This centralize almost alls calls to std::env inside one wrapper
Add a test profile to increase speed for testing (5min -> 20sec on my
machine)
clean a few code style like this:
```
if Some(value) = ...
if value
```
to
```
if Some(true) = ...
```
Co-authored-by: William Escande <wescande@google.com>
