On showing diff/file, use the tab_width specified on .editorconfig, if any (#3241)

Closes #3182

modules/context/repo.go

@@ -6,10 +6,12 @@ package context
 
 import (
 	"fmt"
+	"io/ioutil"
 	"path"
 	"strings"
 
 	"github.com/Unknwon/com"
+	"gopkg.in/editorconfig/editorconfig-core-go.v1"
 	"gopkg.in/macaron.v1"
 
 	"github.com/gogits/git-module"
@@ -69,6 +71,28 @@ func (r *Repository) HasAccess() bool {
 	return r.AccessMode >= models.ACCESS_MODE_READ
 }
 
+// GetEditorconfig returns the .editorconfig definition if found in the
+// HEAD of the default repo branch.
+func (r *Repository) GetEditorconfig() (*editorconfig.Editorconfig, error) {
+	commit, err := r.GitRepo.GetBranchCommit(r.Repository.DefaultBranch)
+	if err != nil {
+		return nil, err
+	}
+	treeEntry, err := commit.GetTreeEntryByPath(".editorconfig")
+	if err != nil {
+		return nil, err
+	}
+	reader, err := treeEntry.Blob().Data()
+	if err != nil {
+		return nil, err
+	}
+	data, err := ioutil.ReadAll(reader)
+	if err != nil {
+		return nil, err
+	}
+	return editorconfig.ParseBytes(data)
+}
+
 func RetrieveBaseRepo(ctx *Context, repo *models.Repository) {
 	// Non-fork repository will not return error in this method.
 	if err := repo.GetBaseRepo(); err != nil {

modules/template/template.go

@@ -17,6 +17,7 @@ import (
 
 	"golang.org/x/net/html/charset"
 	"golang.org/x/text/transform"
+	"gopkg.in/editorconfig/editorconfig-core-go.v1"
 
 	"github.com/gogits/gogs/models"
 	"github.com/gogits/gogs/modules/base"
@@ -109,6 +110,15 @@ func NewFuncMap() []template.FuncMap {
 			mimeType := mime.TypeByExtension(filepath.Ext(filename))
 			return strings.HasPrefix(mimeType, "image/")
 		},
+		"TabSizeClass": func(ec *editorconfig.Editorconfig, filename string) string {
+			if ec != nil {
+				def := ec.GetDefinitionForFilename(filename)
+				if def.TabWidth > 0 {
+					return fmt.Sprintf("tab-size-%d", def.TabWidth)
+				}
+			}
+			return "tab-size-8"
+		},
 	}}
 }