Add error conversion

Cargo.toml

@@ -14,5 +14,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+anyhow = "1.0.75"
 cargo-util = "0.2.6"
 git2 = "0.18.1"
+thiserror = "1.0.50"

src/error.rs

@@ -1,51 +1,43 @@
-use std::{error::Error, fmt::Display};
+use thiserror::Error;
 
 /// Enumerates the possible error values that can be generated by this crate
-#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
+#[derive(Error, Debug)]
 #[non_exhaustive]
 pub enum VSCError {
     /// Unable to detect a version control system
+    #[error("no vcs")]
     NoVCS,
     /// Found a type of file that was not allowed. Includes listing of disallowed files found
+    #[error("{}", format_disallowed_files(dirty_files, staged_files))]
     NotAllowedFilesFound {
         /// Dirty files found (note this will be empty if dirty files are allowed)
         dirty_files: Vec<String>,
         /// Staged files found (note this will be empty if staged files are allowed)
         staged_files: Vec<String>,
     },
+    /// Errors produced outside of the ones from this library
+    #[error(transparent)]
+    Other(#[from] anyhow::Error), // source and Display delegate to anyhow::Error
 }
 
-impl Display for VSCError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            VSCError::NoVCS => write!(f, "no VCS found but this not allowed"),
-            VSCError::NotAllowedFilesFound {
-                dirty_files,
-                staged_files,
-            } => {
-                let mut files_list = String::new();
-                for file in dirty_files {
-                    files_list.push_str("  * ");
-                    files_list.push_str(file);
-                    files_list.push_str(" (dirty)\n");
-                }
-                for file in staged_files {
-                    files_list.push_str("  * ");
-                    files_list.push_str(file);
-                    files_list.push_str(" (staged)\n");
-                }
-
-                write!(
-                    f,
-                    "disallowed files found:\n\
-                     \n\
-                     {}\n\
-                     ",
-                    files_list
-                )
-            }
-        }
+fn format_disallowed_files(dirty_files: &[String], staged_files: &[String]) -> String {
+    let mut files_list = String::new();
+    for file in dirty_files {
+        files_list.push_str("  * ");
+        files_list.push_str(file);
+        files_list.push_str(" (dirty)\n");
+    }
+    for file in staged_files {
+        files_list.push_str("  * ");
+        files_list.push_str(file);
+        files_list.push_str(" (staged)\n");
     }
-}
 
-impl Error for VSCError {}
+    format!(
+        "disallowed files found:\n\
+         \n\
+         {}\n\
+         ",
+        files_list
+    )
+}