Add "reformat with rustfmt" action

Basically, run cargo fmt on the current file. Use this to run execute cargo. Path to Cargo is available via SDK. You’ll need the skip-children rustfmt flag.

Relevant docs: http://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/creating_an_action.html http://www.jetbrains.org/intellij/sdk/docs/basics/action_system.html http://www.jetbrains.org/intellij/sdk/docs/basics/getting_started/creating_an_action.html

[matklad]

If you invoke cargo fmt then it will look inside .cargo/bin regardless of PATH. To pass arguments to rustfmt, you can use --:

cargo fmt -- --skip_children 

[zjhmale]

@matklad one more question is that if i use rustfmt it will just format the specific file but if i use cargo fmt it will format the super mod file either, just like the verbose progress message shown below.

0:42:52 › λ -> cargo fmt -v -- --write-mode=overwrite --skip-children ./src/bar.rs
[Lib] "/Users/xxx/Documents/rustspace/phrase/src/lib.rs"
rustfmt --write-mode=overwrite --skip-children ./src/bar.rs /Users/zjh/Documents/rustspace/phrase/src/lib.rs

0:43:36 › λ -> rustfmt -v --write-mode=overwrite --skip-children ./src/bar.rs
Formatting ./src/bar.rs

is it an expected behavior here?