Abstract over home::

The home crate also accesses global process state, so we need to
abstract over it as well.

Cargo.toml

@@ -113,3 +113,6 @@ codegen-units = 1
 # Reduce build time by setting proc-macro crates non optimized.
 [profile.release.build-override]
 opt-level = 0
+
+[patch.crates-io]
+home = { path = "../rustup-home" }

src/currentprocess.rs

@@ -14,6 +14,7 @@ use rand::{thread_rng, Rng};
 pub mod argsource;
 pub mod cwdsource;
 pub mod filesource;
+mod homethunk;
 pub mod varsource;
 
 use argsource::*;

src/currentprocess/homethunk.rs

@@ -0,0 +1,21 @@
+/// Adapts currentprocess to the trait home::Env
+use std::ffi::OsString;
+use std::io;
+use std::ops::Deref;
+use std::path::PathBuf;
+
+use super::CurrentDirSource;
+use super::CurrentProcess;
+use super::VarSource;
+
+impl home::Env for Box<dyn CurrentProcess + 'static> {
+    fn home_dir(&self) -> Option<PathBuf> {
+        self.var("HOME").ok().map(|v| v.into())
+    }
+    fn current_dir(&self) -> Result<PathBuf, io::Error> {
+        CurrentDirSource::current_dir(self.deref())
+    }
+    fn var_os(&self, key: &str) -> Option<OsString> {
+        VarSource::var_os(self.deref(), key)
+    }
+}

src/utils/utils.rs

@@ -466,11 +466,11 @@ pub fn to_absolute<P: AsRef<Path>>(path: P) -> Result<PathBuf> {
 }
 
 pub fn home_dir() -> Option<PathBuf> {
-    home::home_dir()
+    home::home_dir_from(&process())
 }
 
 pub fn cargo_home() -> Result<PathBuf> {
-    home::cargo_home().map_err(|e| Error::from_kind(ErrorKind::Io(e)))
+    home::cargo_home_from(&process()).map_err(|e| Error::from_kind(ErrorKind::Io(e)))
 }
 
 // Creates a ~/.rustup folder
@@ -496,7 +496,7 @@ pub fn rustup_home_in_user_dir() -> Result<PathBuf> {
 }
 
 pub fn rustup_home() -> Result<PathBuf> {
-    home::rustup_home().map_err(|e| Error::from_kind(ErrorKind::Io(e)))
+    home::rustup_home_from(&process()).map_err(|e| Error::from_kind(ErrorKind::Io(e)))
 }
 
 pub fn format_path_for_display(path: &str) -> String {