Update account manager config parsing

eth2/utils/eth2_config/src/lib.rs

@@ -1,5 +1,6 @@
 use clap::ArgMatches;
 use serde_derive::{Deserialize, Serialize};
+use std::fs;
 use std::fs::File;
 use std::io::prelude::*;
 use std::path::PathBuf;
@@ -104,3 +105,15 @@ where
         Ok(None)
     }
 }
+
+pub fn get_data_dir(args: &ArgMatches, default_data_dir: PathBuf) -> Result<PathBuf, &'static str> {
+    if let Some(data_dir) = args.value_of("data_dir") {
+        Ok(PathBuf::from(data_dir))
+    } else {
+        let path = dirs::home_dir()
+            .ok_or_else(|| "Unable to locate home directory")?
+            .join(&default_data_dir);
+        fs::create_dir_all(&path).map_err(|_| "Unable to create data_dir")?;
+        Ok(path)
+    }
+}