allow embassy-cli not as root (#1501)

* allow embassy-cli not as root
* clean up merge

backend/src/util/config.rs

@@ -0,0 +1,56 @@
+use std::fs::File;
+use std::path::{Path, PathBuf};
+
+use serde::Deserialize;
+use serde_json::Value;
+
+use crate::util::serde::IoFormat;
+use crate::{Config, Error, ResultExt};
+
+pub const CONFIG_PATH: &str = "/etc/embassy/config.yaml";
+pub const CONFIG_PATH_LOCAL: &str = ".embassy/config.yaml";
+
+pub fn local_config_path() -> Option<PathBuf> {
+    if let Ok(home) = std::env::var("HOME") {
+        Some(Path::new(&home).join(CONFIG_PATH_LOCAL))
+    } else {
+        None
+    }
+}
+
+/// BLOCKING
+pub fn load_config_from_paths<'a, T: for<'de> Deserialize<'de>>(
+    paths: impl IntoIterator<Item = impl AsRef<Path>>,
+) -> Result<T, Error> {
+    let mut config = Default::default();
+    for path in paths {
+        if path.as_ref().exists() {
+            let format: IoFormat = path
+                .as_ref()
+                .extension()
+                .and_then(|s| s.to_str())
+                .map(|f| f.parse())
+                .transpose()?
+                .unwrap_or_default();
+            let new = format.from_reader(File::open(path)?)?;
+            config = merge_configs(config, new);
+        }
+    }
+    serde_json::from_value(Value::Object(config)).with_kind(crate::ErrorKind::Deserialization)
+}
+
+pub fn merge_configs(mut first: Config, second: Config) -> Config {
+    for (k, v) in second.into_iter() {
+        let new = match first.remove(&k) {
+            None => v,
+            Some(old) => match (old, v) {
+                (Value::Object(first), Value::Object(second)) => {
+                    Value::Object(merge_configs(first, second))
+                }
+                (first, _) => first,
+            },
+        };
+        first.insert(k, new);
+    }
+    first
+}

backend/src/util/mod.rs

@@ -10,22 +10,21 @@ use std::task::{Context, Poll};
 use async_trait::async_trait;
 use clap::ArgMatches;
 use color_eyre::eyre::{self, eyre};
-use digest::Digest;
 use fd_lock_rs::FdLock;
 use futures::future::BoxFuture;
 use futures::FutureExt;
+pub use helpers::NonDetachingJoinHandle;
 use lazy_static::lazy_static;
+pub use models::Version;
 use pin_project::pin_project;
+use sha2_old::Digest;
 use tokio::fs::File;
 use tokio::sync::{Mutex, OwnedMutexGuard, RwLock};
 use tracing::instrument;
 
 use crate::shutdown::Shutdown;
 use crate::{Error, ResultExt as _};
-
-
-pub use helpers::NonDetachingJoinHandle;
-pub use models::Version;
+pub mod config;
 pub mod io;
 pub mod logger;
 pub mod serde;
@@ -251,7 +250,6 @@ where
     }
 }
 
-
 pub struct GeneralGuard<F: FnOnce() -> T, T = ()>(Option<F>);
 impl<F: FnOnce() -> T, T> GeneralGuard<F, T> {
     pub fn new(f: F) -> Self {