message: tests: Insulate from user git environment
  Several tests in "cargo test" would fail if the user had any of the Git
  environment variables set for name or email address, because those
  environment variables would override the tested configuration.  Filter
  out those environment variables.
diff: @@ -55,6 +55,11 @@ fn _process(t: &OsStr) -> cargo::util::ProcessBuilder {
  .env_remove("CARGO_INCREMENTAL")
  .env_remove("XDG_CONFIG_HOME") // see #2345
  .env("GIT_CONFIG_NOSYSTEM", "1") // keep trying to sandbox ourselves
  + .env_remove("EMAIL")
  + .env_remove("GIT_AUTHOR_NAME")
  + .env_remove("GIT_AUTHOR_EMAIL")
  + .env_remove("GIT_COMMITTER_NAME")
  + .env_remove("GIT_COMMITTER_EMAIL")
  .env_remove("CARGO_TARGET_DIR") // we assume 'target'
  .env_remove("MSYSTEM"); // assume cmd.exe everywhere on windows
  