Calculate filename hash only once (#19654)

* Calculate hash only once.

* remove unused Sha1 template helper function, use ctx.Data["FileNameHash"]

* fix unit tests

services/gitdiff/gitdiff.go

@@ -25,6 +25,7 @@ import (
 	pull_model "code.gitea.io/gitea/models/pull"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/analyze"
+	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/charset"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/highlight"
@@ -604,6 +605,7 @@ func (diffSection *DiffSection) GetComputedInlineDiffFor(diffLine *DiffLine) Dif
 // DiffFile represents a file diff.
 type DiffFile struct {
 	Name                      string
+	NameHash                  string
 	OldName                   string
 	Index                     int
 	Addition, Deletion        int
@@ -952,7 +954,6 @@ parsingLoop:
 				break curFileLoop
 			}
 		}
-
 	}
 
 	// TODO: There are numerous issues with this:
@@ -964,6 +965,8 @@ parsingLoop:
 	diffLineTypeBuffers[DiffLineAdd] = new(bytes.Buffer)
 	diffLineTypeBuffers[DiffLineDel] = new(bytes.Buffer)
 	for _, f := range diff.Files {
+		f.NameHash = base.EncodeSha1(f.Name)
+
 		for _, buffer := range diffLineTypeBuffers {
 			buffer.Reset()
 		}