Merge branch 'master' into 'master'

Cargo.lock

src/lib/builtins/command_info.rs

src/lib/builtins/exists.rs

src/lib/builtins/mod.rs

src/lib/builtins/variables.rs

src/lib/parser/loops/for_grammar.rs

src/lib/shell/assignments.rs

src/lib/shell/binary/prompt.rs

src/lib/shell/binary/readln.rs

src/lib/shell/completer.rs

src/lib/shell/flow.rs

src/lib/shell/flow_control.rs

src/lib/shell/fork_function.rs

src/lib/shell/mod.rs

src/lib/shell/pipe_exec/mod.rs

src/lib/shell/variables/mod.rs