Merge branch 'remove-get-variables' into 'master'

src/binary/history.rs

src/binary/mod.rs

src/binary/prompt.rs

src/lib/builtins/command_info.rs

src/lib/builtins/exists.rs

src/lib/builtins/is.rs

src/lib/builtins/mod.rs

src/lib/builtins/set.rs

src/lib/builtins/variables.rs

src/lib/shell/assignments.rs

src/lib/shell/directory_stack.rs

src/lib/shell/flow.rs

src/lib/shell/fork.rs

src/lib/shell/job.rs

src/lib/shell/mod.rs

src/lib/shell/pipe_exec/mod.rs

src/lib/shell/shell_expand.rs

src/lib/shell/variables/mod.rs