Add better ModTime in gitfs and ArchGitTime helper (for `SOURCE…

…_DATE_EPOCH`)

cmd/bashbrew/git.go

@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"strings"
+	"time"
 
 	"github.com/urfave/cli"
 
@@ -110,6 +111,21 @@ func (r Repo) archGitFS(arch string, entry *manifest.Manifest2822Entry) (fs.FS,
 	return fs.Sub(gitFS, entry.ArchDirectory(arch))
 }
 
+// returns the timestamp of the ArchGitCommit -- useful for SOURCE_DATE_EPOCH
+func (r Repo) ArchGitTime(arch string, entry *manifest.Manifest2822Entry) (time.Time, error) {
+	f, err := r.archGitFS(arch, entry)
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	fi, err := fs.Stat(f, ".")
+	if err != nil {
+		return time.Time{}, err
+	}
+
+	return fi.ModTime(), nil
+}
+
 func gitCommitFS(commit string) (fs.FS, error) {
 	if err := ensureGitInit(); err != nil {
 		return nil, err

pkg/gitfs/fs.go

@@ -17,6 +17,17 @@ import (
 
 // https://github.com/go-git/go-git/issues/296
 
+func CommitTime(commit *goGitPlumbingObject.Commit) time.Time {
+	if commit == nil {
+		return time.Time{}
+	}
+	if commit.Author.When.After(commit.Committer.When) {
+		return commit.Author.When
+	} else {
+		return commit.Committer.When
+	}
+}
+
 func CommitHash(repo *goGit.Repository, commit string) (fs.FS, error) {
 	gitCommit, err := repo.CommitObject(goGitPlumbing.NewHash(commit))
 	if err != nil {
@@ -31,6 +42,7 @@ func CommitHash(repo *goGit.Repository, commit string) (fs.FS, error) {
 			storer: repo.Storer,
 			tree:   tree,
 			name:   ".",
+			Mod:    CommitTime(gitCommit),
 		},
 	}, nil
 }
@@ -49,6 +61,8 @@ type gitFS struct {
 	tree   *goGitPlumbingObject.Tree
 	entry  *goGitPlumbingObject.TreeEntry // might be nil ("." at the top-level of the repo)
 
+	Mod time.Time
+
 	// cached values
 	name string // full path from the repository root
 	size int64  // Tree.Size value for non-directories (more efficient than opening/reading the blob)
@@ -343,7 +357,7 @@ func (f gitFS) Mode() fs.FileMode {
 
 // https://pkg.go.dev/io/fs#FileInfo: modification time
 func (f gitFS) ModTime() time.Time {
-	return time.Time{} // TODO maybe pass down whichever is more recent of commit.Author.When vs commit.Committer.When ?
+	return f.Mod
 }
 
 // https://pkg.go.dev/io/fs#FileInfo: abbreviation for Mode().IsDir()