Use shared repo directories to avoid duplicate checkouts.

src/config/root.rs

@@ -63,6 +63,7 @@ impl Config {
         Ok(target_config)
     }
 
+    /// The root directory where all the output is stored.
     pub(crate) fn get_output_directory(&self) -> Result<Cow<'_, Path>, CustomError> {
         let maybe_repo_directory = self.output_directory.as_deref().map(Cow::Borrowed);
         if let Some(work_dir) = maybe_repo_directory {

src/config/target.rs

@@ -3,6 +3,8 @@ use std::path::Path;
 
 use serde::Deserialize;
 use serde::Serialize;
+use sha2::Digest;
+use sha2::Sha256;
 
 use crate::error::CustomError;
 
@@ -34,13 +36,31 @@ pub(crate) struct TargetConfig {
 }
 
 impl TargetConfig {
+    /// The folder that contains the folders for the build targets.
+    pub(crate) fn get_target_root_directory<'target, 'root>(
+        &'target self,
+        config_root: &'root Config,
+    ) -> Result<Cow<'target, Path>, CustomError> {
+        let output_directory = config_root.get_output_directory()?;
+        Ok(Cow::Owned(output_directory.join("target")))
+    }
+
     /// The root directory for this specific build target.
     pub(crate) fn get_target_directory<'target, 'root>(
         &'target self,
         config_root: &'root Config,
     ) -> Result<Cow<'target, Path>, CustomError> {
-        let repo_directory = config_root.get_output_directory()?;
-        Ok(Cow::Owned(repo_directory.join(&self.name)))
+        let target_root = self.get_target_root_directory(config_root)?;
+        Ok(Cow::Owned(target_root.join(&self.name)))
+    }
+
+    /// The folder that contains the folders containing the checkouts of the git repositories.
+    pub(crate) fn get_repo_root_directory<'target, 'root>(
+        &'target self,
+        config_root: &'root Config,
+    ) -> Result<Cow<'target, Path>, CustomError> {
+        let output_directory = config_root.get_output_directory()?;
+        Ok(Cow::Owned(output_directory.join("repo")))
     }
 
     /// The root of the checkout of the git repository.
@@ -48,8 +68,11 @@ impl TargetConfig {
         &'target self,
         config_root: &'root Config,
     ) -> Result<Cow<'target, Path>, CustomError> {
-        let target_directory = self.get_target_directory(config_root)?;
-        Ok(Cow::Owned(target_directory.join("repo")))
+        let hashed_repo = Sha256::digest(&self.repo);
+        let hashed_repo = hex_string(&hashed_repo);
+
+        let repo_root = self.get_repo_root_directory(config_root)?;
+        Ok(Cow::Owned(repo_root.join(hashed_repo)))
     }
 
     /// The directory that contains flake.nix.
@@ -99,3 +122,11 @@ impl TargetConfig {
         Ok(&self.attr)
     }
 }
+
+fn hex_string(data: &[u8]) -> String {
+    let mut out = String::with_capacity(data.len() * 2);
+    for byte in data {
+        out.push_str(format!("{:02x}", byte).as_str());
+    }
+    out
+}