rust: Update to 2018 edition

This mostly involves adjusting our path uses to be anchored, e.g. at
`self::` or `crate::`. I took the opportunity to also tweak `use`
ordering so that we consistently list modules in external crates first
before our own.

Closes: #1812
Approved by: lucab

rust/Cargo.toml

@@ -2,6 +2,7 @@
 name = "rpmostree-rust"
 version = "0.1.0"
 authors = ["Colin Walters <walters@verbum.org>", "Jonathan Lebon <jonathan@jlebon.com>"]
+edition = "2018"
 
 [dependencies]
 failure = "0.1.3"

rust/src/composepost.rs

@@ -23,7 +23,7 @@ use std::io;
 use std::io::{BufRead, Write};
 use std::path::Path;
 
-use openat_utils::OpenatDirExt;
+use crate::openat_utils::OpenatDirExt;
 
 // rpm-ostree uses /home → /var/home by default as generated by our
 // rootfs; we don't expect people to change this.  Let's be nice
@@ -37,7 +37,7 @@ use openat_utils::OpenatDirExt;
 fn postprocess_useradd(rootfs_dfd: &openat::Dir) -> Fallible<()> {
     let path = Path::new("usr/etc/default/useradd");
     if let Some(f) = rootfs_dfd.open_file_optional(path)? {
-        let mut f = io::BufReader::new(f);
+        let f = io::BufReader::new(f);
         let tmp_path = path.parent().unwrap().join("useradd.tmp");
         let o = rootfs_dfd.write_file(&tmp_path, 0o644)?;
         let mut bufw = io::BufWriter::new(&o);
@@ -82,7 +82,7 @@ enable ostree-finalize-staged.path
 fn postprocess_subs_dist(rootfs_dfd: &openat::Dir) -> Fallible<()> {
     let path = Path::new("usr/etc/selinux/targeted/contexts/files/file_contexts.subs_dist");
     if let Some(f) = rootfs_dfd.open_file_optional(path)? {
-        let mut f = io::BufReader::new(f);
+        let f = io::BufReader::new(f);
         let tmp_path = path.parent().unwrap().join("file_contexts.subs_dist.tmp");
         let o = rootfs_dfd.write_file(&tmp_path, 0o644)?;
         let mut bufw = io::BufWriter::new(&o);
@@ -117,10 +117,11 @@ fn compose_postprocess_final(rootfs_dfd: &openat::Dir) -> Fallible<()> {
 
 mod ffi {
     use super::*;
-    use ffiutil::*;
     use glib_sys;
     use libc;
 
+    use crate::ffiutil::*;
+
     #[no_mangle]
     pub extern "C" fn ror_compose_postprocess_final(
         rootfs_dfd: libc::c_int,

rust/src/ffiutil.rs

@@ -19,6 +19,7 @@
 use gio_sys;
 use glib_sys;
 use libc;
+use openat;
 use std::ffi::CString;
 use std::ffi::{CStr, OsStr};
 use std::fmt::Display;
@@ -26,8 +27,6 @@ use std::os::unix::ffi::OsStrExt;
 use std::os::unix::io::{FromRawFd, IntoRawFd};
 use std::ptr;
 
-use openat;
-
 /* Helper functions for FFI between C and Rust.
  *
  * This code assumes that it was compiled with the system allocator:

rust/src/journal.rs

@@ -147,9 +147,11 @@ fn journal_print_staging_failure() -> Fallible<()> {
 
 mod ffi {
     use super::*;
-    use ffiutil::*;
     use glib_sys;
     use libc;
+
+    use crate::ffiutil::*;
+
     #[no_mangle]
     pub extern "C" fn ror_journal_print_staging_failure(
         gerror: *mut *mut glib_sys::GError,

rust/src/lib.rs

@@ -39,15 +39,15 @@ extern crate serde_json;
 extern crate serde_yaml;
 
 mod ffiutil;
-
-mod treefile;
-pub use treefile::*;
-mod composepost;
-pub use composepost::*;
-mod progress;
-pub use progress::*;
-mod journal;
-pub use journal::*;
-mod utils;
-pub use utils::*;
 mod openat_utils;
+
+mod composepost;
+pub use self::composepost::*;
+mod journal;
+pub use self::journal::*;
+mod progress;
+pub use self::progress::*;
+mod treefile;
+pub use self::treefile::*;
+mod utils;
+pub use self::utils::*;

rust/src/progress.rs

@@ -168,10 +168,11 @@ mod tests {
 
 mod ffi {
     use super::*;
-    use ffiutil::*;
     use libc;
     use std::sync::MutexGuard;
 
+    use crate::ffiutil::*;
+
     fn assert_empty(m: &MutexGuard<Option<ProgressState>>) {
         if let Some(ref state) = **m {
             panic!("Overwriting task: \"{}\"", state.message)

rust/src/treefile.rs

@@ -30,7 +30,8 @@ use std::collections::HashMap;
 use std::io::prelude::*;
 use std::path::Path;
 use std::{collections, fs, io};
-use utils;
+
+use crate::utils;
 
 const INCLUDE_MAXDEPTH: u32 = 50;
 
@@ -990,14 +991,14 @@ packages:
 
 mod ffi {
     use super::*;
-    use ffiutil::*;
     use glib_sys;
     use libc;
-
     use std::io::Seek;
     use std::os::unix::io::{AsRawFd, RawFd};
     use std::{fs, io, ptr};
 
+    use crate::ffiutil::*;
+
     // Some of our file descriptors may be read multiple times.
     // We try to consistently seek to the start to make that
     // convenient from the C side.  Note that this function

rust/src/utils.rs

@@ -116,7 +116,6 @@ mod tests {
 
 mod ffi {
     use super::*;
-    use ffiutil::*;
     use glib;
     use glib_sys;
     use libc;
@@ -124,6 +123,8 @@ mod ffi {
     use std::os::unix::io::IntoRawFd;
     use std::ptr;
 
+    use crate::ffiutil::*;
+
     #[no_mangle]
     pub extern "C" fn ror_download_to_fd(
         url: *const libc::c_char,