Attach a refs/notes/byre note to each squash merge and push it

internal/git/notes.go

@@ -0,0 +1,75 @@
+package git
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+)
+
+const NotesRef = "refs/notes/byre"
+
+const notesFetch = NotesRef + "*:" + NotesRef + "*"
+
+func ConfigureNotesFetch(repo string) error {
+	key := "remote." + Remote + ".fetch"
+	out, stderr, code, err := runCode(repo, nil, "config", "--get-all", key)
+	if err != nil {
+		return err
+	}
+	if code != 0 && code != 1 {
+		return fmt.Errorf("git config --get-all %s: exit status %d: %s", key, code, stderr)
+	}
+	if slices.Contains(strings.Split(out, "\n"), notesFetch) {
+		return nil
+	}
+	_, err = run(repo, "config", "--add", key, notesFetch)
+	return err
+}
+
+func NoteCommit(repo, commit, note string, env []string) (string, error) {
+	blob, err := runInput(repo, nil, note, "hash-object", "-w", "--stdin")
+	if err != nil {
+		return "", err
+	}
+
+	parent, stderr, code, err := runCode(repo, nil, "rev-parse", "--verify", "--quiet", NotesRef)
+	if err != nil {
+		return "", err
+	}
+	if code != 0 && code != 1 {
+		return "", fmt.Errorf("git rev-parse %s: exit status %d: %s", NotesRef, code, stderr)
+	}
+
+	dir, err := os.MkdirTemp("", "byre-notes-*")
+	if err != nil {
+		return "", err
+	}
+	defer os.RemoveAll(dir)
+	index := []string{"GIT_INDEX_FILE=" + filepath.Join(dir, "index")}
+
+	commitArgs := []string{"commit-tree", "-m", "Notes added by byre"}
+	if code == 0 {
+		_, err = runEnv(repo, index, "read-tree", parent)
+		if err != nil {
+			return "", err
+		}
+		commitArgs = append(commitArgs, "-p", parent)
+	}
+	_, err = runEnv(repo, index, "update-index", "--add", "--cacheinfo", "100644,"+blob+","+commit)
+	if err != nil {
+		return "", err
+	}
+	tree, err := runEnv(repo, index, "write-tree")
+	if err != nil {
+		return "", err
+	}
+
+	return runEnv(repo, env, append(commitArgs, tree)...)
+}
+
+func SetNotes(repo, notes string) error {
+	_, err := run(repo, "update-ref", NotesRef, notes)
+	return err
+}