4 files changed, 70 insertions, 9 deletions

diff --git a/pkg/git/git.go b/pkg/git/git.go
index 9139261..7fc28fa 100644
--- a/pkg/git/git.go
+++ b/pkg/git/git.go
@@ -31,7 +31,7 @@ func Branches(repoDir string, filter *regexp.Regexp, defaultBranch string) ([]Re
 		if filter != nil && !filter.MatchString(line) && line != defaultBranch {
 			continue
 		}
-		branches = append(branches, Ref(line))
+		branches = append(branches, NewRef(line))
 	}
 	return branches, nil
 }
@@ -88,13 +88,13 @@ func Tags(repoDir string) ([]Tag, error) {
 }
 
 func Files(ref Ref, repoDir string) ([]Blob, error) {
-	if ref == "" {
-		ref = "HEAD"
+	if ref.IsEmpty() {
+		ref = NewRef("HEAD")
 	}
 
 	// -r: recurse into subtrees
 	// -l: include blob size
-	cmd := exec.Command("git", "ls-tree", "--full-tree", "-r", "-l", string(ref))
+	cmd := exec.Command("git", "ls-tree", "--full-tree", "-r", "-l", ref.Ref())
 	if repoDir != "" {
 		cmd.Dir = repoDir
 	}
@@ -196,11 +196,11 @@ func Files(ref Ref, repoDir string) ([]Blob, error) {
 }
 
 func BlobContent(ref Ref, path string, repoDir string) ([]byte, bool, error) {
-	if ref == "" {
-		ref = "HEAD"
+	if ref.IsEmpty() {
+		ref = NewRef("HEAD")
 	}
 	// Use `git show ref:path` to get the blob content at that ref
-	cmd := exec.Command("git", "show", string(ref)+":"+path)
+	cmd := exec.Command("git", "show", ref.Ref()+":"+path)
 	if repoDir != "" {
 		cmd.Dir = repoDir
 	}
@@ -233,7 +233,7 @@ func Commits(ref Ref, repoDir string) ([]Commit, error) {
 		"--date=unix",
 		"--pretty=format:" + strings.Join(format, "\x1F"),
 		"-z", // Separate the commits with NULs instead of newlines
-		string(ref),
+		ref.Ref(),
 	}
 
 	cmd := exec.Command("git", args...)
diff --git a/pkg/git/types.go b/pkg/git/types.go
index 3c12f14..121c7d8 100644
--- a/pkg/git/types.go
+++ b/pkg/git/types.go
@@ -4,7 +4,29 @@ import (
 	"time"
 )
 
-type Ref string
+type Ref struct {
+	ref     string
+	dirName string
+}
+
+func NewRef(ref string) Ref {
+	return Ref{
+		ref:     ref,
+		dirName: RefToFileName(ref),
+	}
+}
+
+func (r Ref) IsEmpty() bool {
+	return r.ref == ""
+}
+
+func (r Ref) Ref() string {
+	return r.ref
+}
+
+func (r Ref) DirName() string {
+	return r.dirName
+}
 
 type Blob struct {
 	Ref      Ref
diff --git a/pkg/git/utils.go b/pkg/git/utils.go
index 24a2b75..68e4497 100644
--- a/pkg/git/utils.go
+++ b/pkg/git/utils.go
@@ -3,6 +3,7 @@ package git
 import (
 	"fmt"
 	"strconv"
+	"strings"
 )
 
 // ParseFileMode converts a git-style file mode (e.g. "100644")
@@ -74,3 +75,17 @@ func IsBinary(b []byte) bool {
 	// If more than 30% of sampled bytes are non-text, consider binary
 	return bad*100 > n*30
 }
+
+func RefToFileName(ref string) string {
+	var result strings.Builder
+	for _, c := range ref {
+		if (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '-' || c == '.' {
+			result.WriteByte(byte(c))
+		} else if c >= 'A' && c <= 'Z' {
+			result.WriteByte(byte(c - 'A' + 'a'))
+		} else {
+			result.WriteByte('-')
+		}
+	}
+	return result.String()
+}
diff --git a/pkg/git/utils_test.go b/pkg/git/utils_test.go
index ecbe952..4dcebe8 100644
--- a/pkg/git/utils_test.go
+++ b/pkg/git/utils_test.go
@@ -54,3 +54,27 @@ func TestParseFileModeInvalid(t *testing.T) {
 		})
 	}
 }
+
+func TestRefToFileName(t *testing.T) {
+	tests := []struct {
+		in   string
+		want string
+	}{
+		{"main", "main"},
+		{"master", "master"},
+		{"release/v1.0", "release-v1.0"},
+		{"feature/add-login", "feature-add-login"},
+		{"bugfix\\windows\\path", "bugfix-windows-path"},
+		{"1.0.0", "1.0.0"},
+		{"1.x", "1.x"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.in, func(t *testing.T) {
+			got := git.RefToFileName(tt.in)
+			if got != tt.want {
+				t.Fatalf("refToFileName(%q) = %q, want %q", tt.in, got, tt.want)
+			}
+		})
+	}
+}