Retarget intermediate branches during rebase

Author: quodlibetor

src/main.rs

@@ -138,6 +138,13 @@ fn do_rebase_inner(
 ) -> Result<(), anyhow::Error> {
     let sig = repo.signature()?;
 
+    let mut branches: HashMap<Oid, Branch> = HashMap::new();
+    for (branch, _type) in repo.branches(Some(git2::BranchType::Local))?.flatten() {
+        let oid = branch.get().peel_to_commit()?.id();
+        // TODO: handle multiple branches pointing to the same commit
+        branches.insert(oid, branch);
+    }
+
     match rebase.next() {
         Some(ref res) => {
             let op = res.as_ref().map_err(|e| anyhow!("No commit: {}", e))?;
@@ -169,7 +176,12 @@ fn do_rebase_inner(
             Some(Pick) => {
                 let commit = repo.find_commit(op.id())?;
                 if commit.message() != fixup_message {
-                    rebase.commit(None, &sig, None)?;
+                    let new_id = rebase.commit(None, &sig, None)?;
+                    if let Some(branch) = branches.get_mut(&commit.id()) {
+                        branch
+                            .get_mut()
+                            .set_target(new_id, "git-fixup retarget historical branch")?;
+                    }
                 }
             }
             Some(Fixup) | Some(Squash) | Some(Exec) | Some(Edit) | Some(Reword) => {

tests/basic.rs

@@ -76,14 +76,10 @@ fn simple_straightline_commits() {
     let td = assert_fs::TempDir::new().unwrap();
     git_init(&td);
 
-    for n in &["a", "b"] {
-        git_file_commit(n, &td);
-    }
+    git_commits(&["a", "b"], &td);
     git(&["checkout", "-b", "changes"], &td);
     git(&["branch", "-u", "main"], &td);
-    for n in &["target", "d"] {
-        git_file_commit(&n, &td);
-    }
+    git_commits(&["target", "d"], &td);
 
     let log = git_log(&td);
     assert_eq!(
@@ -122,14 +118,10 @@ fn test_no_commit_in_range() {
     let td = assert_fs::TempDir::new().unwrap();
     git_init(&td);
 
-    for n in &["a", "b", "c", "d"] {
-        git_file_commit(n, &td);
-    }
+    git_commits(&["a", "b", "c", "d"], &td);
     git(&["checkout", "-b", "changes", ":/c"], &td);
     git(&["branch", "-u", "main"], &td);
-    for n in &["target", "f", "g"] {
-        git_file_commit(&n, &td);
-    }
+    git_commits(&["target", "f", "g"], &td);
 
     let out = git_log(&td);
     assert_eq!(
@@ -171,9 +163,62 @@ new
     );
 }
 
+#[test]
+fn retarget_branches_in_range() {
+    let td = assert_fs::TempDir::new().unwrap();
+    git_init(&td);
+
+    git_commits(&["a", "b"], &td);
+    git(&["checkout", "-b", "intermediate"], &td);
+    git_commits(&["target", "c", "d"], &td);
+
+    git(&["checkout", "-b", "changes"], &td);
+    git_commits(&["e", "f"], &td);
+
+    let expected = "\
+* f HEAD -> changes
+* e
+* d intermediate
+* c
+* target
+* b main
+* a
+";
+    let out = git_log(&td);
+    assert_eq!(out, expected, "log:\n{}\nexpected:\n{}", out, expected);
+
+    td.child("new").touch().unwrap();
+    git(&["add", "new"], &td);
+
+    fixup(&td).args(&["-P", "target"]).assert().success();
+
+    let (files, err) = git_changed_files("target", &td);
+
+    assert_eq!(
+        files,
+        "\
+file_target
+new
+",
+        "out: {} err: {}",
+        files,
+        err
+    );
+
+    // should be identical to before
+    let out = git_log(&td);
+    assert_eq!(out, expected, "\nactual:\n{}\nexpected:\n{}", out, expected);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Helpers
 
+fn git_commits(ids: &[&str], tempdir: &assert_fs::TempDir) {
+    for n in ids {
+        git_file_commit(n, &tempdir);
+    }
+}
+
 fn git_init(tempdir: &assert_fs::TempDir) {
     git(&["init", "--initial-branch=main"], &tempdir);
     git(&["config", "user.email", "[email protected]"], &tempdir);