1 files changed, 85 insertions, 0 deletions
diff --git a/autogen.go b/autogen.go
new file mode 100644
index 0000000..b157d03
--- /dev/null
+++ b/autogen.go
@@ -0,0 +1,85 @@
+package gitpb
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// files   : a list of files to save ["go.mod", "go.sum"]
+// refname : could be "master" or "v0.1.5" or "a605119c2cc41"
+// del     : true means empty out existing notes, otherwise append
+func (repo *Repo) AutogenSave(files []string, refname string, del bool) error {
+	if del {
+		cmd := []string{"git", "notes", "remove", refname}
+		if err := repo.StrictRun(cmd); err != nil {
+			return err
+		}
+	}
+	for _, fname := range files {
+		autotag := "// `autogen:" + fname + "`"
+		cmd := []string{"git", "notes", "append", "-m", autotag, refname}
+		if err := repo.StrictRun(cmd); err != nil {
+			return err
+		}
+		cmd = []string{"git", "notes", "append", "-F", fname, refname}
+		if err := repo.StrictRun(cmd); err != nil {
+			return err
+		}
+	}
+	// a tag with a blank name indicates the end of the autogen file or files
+	autotag := "// `autogen:`"
+	cmd := []string{"git", "notes", "append", "-m", autotag, refname}
+	if err := repo.StrictRun(cmd); err != nil {
+		return err
+	}
+	return nil
+}
+
+// restores files from git metadata (notes)
+func (repo *Repo) AutogenRestore() error {
+	result := repo.Run([]string{"git", "notes", "show"})
+	if result.Exit != 0 {
+		return errors.New(fmt.Sprint("git notes show returned ", result.Exit))
+	}
+	if result.Error != nil {
+		return result.Error
+	}
+	if len(result.Stdout) == 0 {
+		return nil
+	}
+
+	var newf *os.File
+	var err error
+	var body string
+	for _, line := range result.Stdout {
+		if strings.HasPrefix(line, "// `autogen:") {
+			if newf != nil {
+				fmt.Fprintln(newf, strings.TrimSpace(body))
+				newf.Close()
+				newf = nil
+				body = ""
+			}
+			fbase := strings.TrimPrefix(line, "// `autogen:")
+			fbase = strings.TrimSpace(fbase)
+			fbase = strings.TrimSuffix(fbase, "`")
+			// if line == // `autogen:`  , then the filename is blank
+			if fbase != "" {
+				fname := filepath.Join(filepath.Join(repo.FullPath, fbase))
+				newf, err = os.OpenFile(fname, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
+				if err != nil {
+					return err
+				}
+			}
+			continue
+		}
+		body += line + "\n"
+	}
+	if newf != nil {
+		fmt.Fprintln(newf, strings.TrimSpace(body))
+		newf.Close()
+	}
+	return nil
+}