showRefGrouper: new implementation for --show-ref

Implement `--show-ref` by logging at the `RefGrouper` level rather
than at the `ReferenceFilter` level. This decouples use of the filter
from logging.

Author: mhagger

internal/refopts/ref_group_builder.go

@@ -235,11 +235,6 @@ func (rgb *RefGroupBuilder) Finish() (sizes.RefGrouper, error) {
 		rgb.topLevelGroup.filter = git.AllReferencesFilter
 	}
 
-	if rgb.ShowRefs {
-		fmt.Fprintf(os.Stderr, "References (included references marked with '+'):\n")
-		rgb.topLevelGroup.filter = showRefFilter{rgb.topLevelGroup.filter}
-	}
-
 	refGrouper := refGrouper{
 		topLevelGroup: rgb.topLevelGroup,
 	}
@@ -256,6 +251,11 @@ func (rgb *RefGroupBuilder) Finish() (sizes.RefGrouper, error) {
 		refGrouper.refGroups = append(refGrouper.refGroups, *refGrouper.ignoredRefGroup)
 	}
 
+	if rgb.ShowRefs {
+		fmt.Fprintf(os.Stderr, "References (included references marked with '+'):\n")
+		return showRefGrouper{&refGrouper, os.Stderr}, nil
+	}
+
 	return &refGrouper, nil
 }
 
@@ -313,18 +313,3 @@ func (refGrouper *refGrouper) Categorize(refname string) (bool, []sizes.RefGroup
 func (refGrouper *refGrouper) Groups() []sizes.RefGroup {
 	return refGrouper.refGroups
 }
-
-// showRefFilter is a `git.ReferenceFilter` that logs its choices to Stderr.
-type showRefFilter struct {
-	f git.ReferenceFilter
-}
-
-func (f showRefFilter) Filter(refname string) bool {
-	b := f.f.Filter(refname)
-	if b {
-		fmt.Fprintf(os.Stderr, "+ %s\n", refname)
-	} else {
-		fmt.Fprintf(os.Stderr, "  %s\n", refname)
-	}
-	return b
-}

internal/refopts/show_ref_grouper.go

@@ -0,0 +1,24 @@
+package refopts
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/github/git-sizer/sizes"
+)
+
+// showRefFilter is a `git.ReferenceFilter` that logs its choices to Stderr.
+type showRefGrouper struct {
+	*refGrouper
+	w io.Writer
+}
+
+func (refGrouper showRefGrouper) Categorize(refname string) (bool, []sizes.RefGroupSymbol) {
+	walk, symbols := refGrouper.refGrouper.Categorize(refname)
+	if walk {
+		fmt.Fprintf(refGrouper.w, "+ %s\n", refname)
+	} else {
+		fmt.Fprintf(refGrouper.w, "  %s\n", refname)
+	}
+	return walk, symbols
+}