Allow specifying custom Josh filter

Author: Kobzol

README.md

@@ -13,6 +13,8 @@ $ cargo install --locked --git https://github.com/rust-lang/josh-sync
 
 First, create a configuration file for a given subtree repo using `josh-sync init`. The config will be created under the path `josh-sync.toml`. Modify the file to fill in the name of the subtree repository (e.g. `stdarch`) and its relative path in the main `rust-lang/rust` repository (e.g. `library/stdarch`).
 
+If you need to specify a more complex Josh `filter`, use `filter` field in the configuration file instead of the `path` field.
+
 The `init` command will also create an empty `rust-version` file that stores the last upstream `rustc` SHA that was synced in the subtree.
 
 ## Performing pull

src/bin/josh_sync.rs

@@ -50,7 +50,8 @@ fn main() -> anyhow::Result<()> {
             let config = JoshConfig {
                 org: "rust-lang".to_string(),
                 repo: "<repository-name>".to_string(),
-                path: "<relative-subtree-path>".to_string(),
+                path: Some("<relative-subtree-path>".to_string()),
+                filter: None,
             };
             config
                 .write(Path::new(DEFAULT_CONFIG_PATH))

src/config.rs

@@ -8,14 +8,25 @@ pub struct JoshConfig {
     pub repo: String,
     /// Relative path where the subtree is located in rust-lang/rust.
     /// For example `src/doc/rustc-dev-guide`.
-    pub path: String,
+    pub path: Option<String>,
+    /// Optional filter specification for Josh.
+    /// It cannot be used together with `path`.
+    pub filter: Option<String>,
 }
 
 impl JoshConfig {
     pub fn full_repo_name(&self) -> String {
         format!("{}/{}", self.org, self.repo)
     }
 
+    pub fn construct_josh_filter(&self) -> String {
+        match (&self.path, &self.filter) {
+            (Some(path), None) => format!(":/{path}"),
+            (None, Some(filter)) => filter.clone(),
+            _ => unreachable!("Config contains both path and a filter"),
+        }
+    }
+
     pub fn write(&self, path: &Path) -> anyhow::Result<()> {
         let config = toml::to_string_pretty(self).context("cannot serialize config")?;
         std::fs::write(path, config).context("cannot write config")?;
@@ -31,5 +42,13 @@ pub fn load_config(path: &Path) -> anyhow::Result<JoshConfig> {
     let data = std::fs::read_to_string(path)
         .with_context(|| format!("cannot load config file from {}", path.display()))?;
     let config: JoshConfig = toml::from_str(&data).context("cannot load config as TOML")?;
+    if config.path.is_some() == config.filter.is_some() {
+        return if config.path.is_some() {
+            Err(anyhow::anyhow!("Cannot specify both `path` and `filter`"))
+        } else {
+            Err(anyhow::anyhow!("Must specify one of `path` and `filter`"))
+        };
+    }
+
     Ok(config)
 }

src/sync.rs

@@ -19,11 +19,6 @@ impl From<anyhow::Error> for RustcPullError {
     }
 }
 
-/// Constructs a Josh filter for synchronization, like `:/src/foo`.
-fn construct_filter(path: &str) -> String {
-    format!(":/{path}")
-}
-
 pub struct PullResult {
     pub merge_commit_message: String,
 }
@@ -64,7 +59,7 @@ impl GitSync {
         let josh_url = josh.git_url(
             UPSTREAM_REPO,
             Some(&upstream_sha),
-            &construct_filter(&self.context.config.path),
+            &self.context.config.construct_josh_filter(),
         );
 
         let orig_head = check_output(["git", "rev-parse", "HEAD"])?;
@@ -150,7 +145,7 @@ Upstream ref: {upstream_sha}
 Filtered ref: {incoming_ref}
             "#,
             upstream_head_short = &upstream_sha[..12],
-            filter = construct_filter(&self.context.config.path)
+            filter = self.context.config.construct_josh_filter()
         );
 
         // Merge the fetched commit.
@@ -203,7 +198,7 @@ Filtered ref: {incoming_ref}
         let josh_url = josh.git_url(
             &format!("{username}/rust"),
             None,
-            &construct_filter(&self.context.config.path),
+            &self.context.config.construct_josh_filter(),
         );
         let user_upstream_url = format!("https://github.com/{username}/rust");