BeforeSourcePath should point to base commit (go-gitea#18880)

Author: jpraet

routers/web/repo/compare.go

@@ -77,8 +77,8 @@ func setPathsCompareContext(ctx *context.Context, base, head *git.Commit, headOw
 	ctx.Data["SourcePath"] = SourceCommitURL(headOwner, headName, head)
 	ctx.Data["RawPath"] = RawCommitURL(headOwner, headName, head)
 	if base != nil {
-		ctx.Data["BeforeSourcePath"] = SourceCommitURL(headOwner, headName, head)
-		ctx.Data["BeforeRawPath"] = RawCommitURL(headOwner, headName, head)
+		ctx.Data["BeforeSourcePath"] = SourceCommitURL(headOwner, headName, base)
+		ctx.Data["BeforeRawPath"] = RawCommitURL(headOwner, headName, base)
 	}
 }