Refactor sha1 and time-limited code (#31023)

Remove "EncodeSha1", it shouldn't be used as a general purpose hasher
(just like we have removed "EncodeMD5" in #28622)

Rewrite the "time-limited code" related code and write better tests, the
old code doesn't seem quite right.

services/gitdiff/gitdiff.go

@@ -23,7 +23,6 @@ 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"
@@ -746,7 +745,7 @@ parsingLoop:
 	diffLineTypeBuffers[DiffLineAdd] = new(bytes.Buffer)
 	diffLineTypeBuffers[DiffLineDel] = new(bytes.Buffer)
 	for _, f := range diff.Files {
-		f.NameHash = base.EncodeSha1(f.Name)
+		f.NameHash = git.HashFilePathForWebUI(f.Name)
 
 		for _, buffer := range diffLineTypeBuffers {
 			buffer.Reset()