wip!: variant derivation

Author: oahshtsua

src/lib.rs

@@ -39,6 +39,33 @@ pub fn init(repo: &Repository) -> Result<()> {
     Ok(())
 }
 
+pub fn derive(repo: &Repository, name: &str, features: &[String]) -> Result<()> {
+    println!("Deriving variant '{}' with features: {:?}", name, features);
+    // create a new orphan branch
+    // walk the commit graph
+    let mut revwalk = repo.revwalk()?;
+    revwalk.push_head()?;
+    revwalk.set_sorting(Sort::TOPOLOGICAL | Sort::TIME | Sort::REVERSE)?;
+
+    let target_features: HashSet<String> = features.iter().cloned().collect();
+    for oid in revwalk {
+        let oid = oid?;
+        let commit = repo.find_commit(oid)?;
+
+        let summary = commit.summary().context("Error extracting summary")?;
+        if let Some(feature) = extract_scope(summary) {
+            if target_features.contains(feature) {
+                println!("Applying commit: {} {}", oid, summary);
+            }
+        }
+    }
+
+    // for each commit that is in the specified feature set, extract the delta
+    // put together the delta
+    // add a custom reference to the newly created branch to keep track of variants
+    Ok(())
+}
+
 pub fn diff(repo: &Repository, target: &str, reverse: bool) -> Result<()> {
     let current_ref = repo.head()?;
     let target_ref = repo
@@ -121,6 +148,12 @@ fn extract_change_id(msg: &str) -> Option<String> {
         .and_then(|caps| caps.get(1).map(|m| m.as_str().to_string()))
 }
 
+fn extract_scope(commit: &str) -> Option<&str> {
+    let re = Regex::new(r"^(?P<type>[a-z]+)(?:\((?P<scope>[^)]+)\))?(?P<breaking>!)?:").unwrap();
+    re.captures(commit)
+        .and_then(|caps| caps.name("scope").map(|m| m.as_str()))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -160,4 +193,27 @@ CHANGE_ID: fec54ceb-74fe-4c6e-b467-cee066ffa268abc
         let result = extract_change_id(msg);
         assert_eq!(result, None);
     }
+
+    #[test]
+    fn extracts_scope_when_present() {
+        assert_eq!(extract_scope("feat(auth): add login"), Some("auth"));
+    }
+
+    #[test]
+    fn extracts_scope_with_breaking_change() {
+        assert_eq!(
+            extract_scope("feat(api)!: change response format"),
+            Some("api")
+        );
+    }
+
+    #[test]
+    fn returns_none_when_no_scope() {
+        assert_eq!(extract_scope("fix: missing semicolon"), None);
+    }
+
+    #[test]
+    fn does_not_match_invalid_format() {
+        assert_eq!(extract_scope("not a conventional commit"), None);
+    }
 }

src/main.rs

@@ -2,7 +2,7 @@ use anyhow::{Context, Result};
 use clap::{Parser, Subcommand};
 use git2::Repository;
 
-use git_varcs::{diff, init};
+use git_varcs::{derive, diff, init};
 
 #[derive(Parser)]
 #[command(name = "git-vms", version)]
@@ -15,6 +15,14 @@ struct Cli {
 enum Commands {
     /// Initialize variant management support in the git repository
     Init,
+    /// Derive a new variant from the specified set of features
+    Derive {
+        /// The name of the variant
+        name: String,
+        /// The set of features to use for the derivation
+        #[arg(short, long = "feature", required = true)]
+        features: Vec<String>,
+    },
     /// List the commits exist in the target branch but not in the current branch
     Diff {
         /// The branch to compare against
@@ -33,6 +41,9 @@ fn main() -> Result<()> {
         Commands::Init => {
             init(&repo).context("Failed to initialize VMS support")?;
         }
+        Commands::Derive { name, features } => {
+            derive(&repo, &name, &features).context("Failed to derive variant")?;
+        }
         Commands::Diff { target, reverse } => {
             diff(&repo, &target, reverse).context(format!(
                 "Failed to diff current branch against '{}'",