Refactor LFS SSH and internal routers (#32473)

Gitea instance keeps reporting a lot of errors like "LFS SSH transfer connection denied, pure SSH protocol is disabled". When starting debugging the problem, there are more problems found. Try to address most of them:

* avoid unnecessary server side error logs (change `fail()` to not log them)
* figure out the broken tests/user2/lfs.git (added comments)
* avoid `migratePushMirrors` failure when a repository doesn't exist (ignore them)
* avoid "Authorization" (internal&lfs) header conflicts, remove the tricky "swapAuth" and use "X-Gitea-Internal-Auth"
* make internal token comparing constant time (it wasn't a serous problem because in a real world it's nearly impossible to timing-attack the token, but good to fix and backport)
* avoid duplicate routers (introduce AddOwnerRepoGitLFSRoutes)
* avoid "internal (private)" routes using session/web context (they should use private context)
* fix incorrect "path" usages (use "filepath")
* fix incorrect mocked route point handling (need to check func nil correctly)
* split some tests from "git general tests" to "git misc tests" (to keep "git_general_test.go" simple)

Still no correct result for Git LFS SSH tests. So the code is kept there
(`tests/integration/git_lfs_ssh_test.go`) and a FIXME explains the details.

models/fixtures/lfs_meta_object.yml

@@ -1,4 +1,11 @@
 # These are the LFS objects in user2/lfs.git
+# user2/lfs is an INVALID repository
+#
+#  commit e9c32647bab825977942598c0efa415de300304b (HEAD -> master)
+#  Author: Rowan Bohde <rowan.bohde@gmail.com>
+#  Date:   Thu Aug 1 14:38:23 2024 -0500
+#
+#      add invalid lfs file
 -
 
   id: 1
@@ -11,7 +18,7 @@
 
   id: 2
   oid: 2eccdb43825d2a49d99d542daa20075cff1d97d9d2349a8977efe9c03661737c
-  size: 107
+  size: 107 # real size is 2048
   repository_id: 54
   created_unix: 1671607299
 
@@ -30,3 +37,12 @@
   size: 25
   repository_id: 54
   created_unix: 1671607299
+
+# this file is missing
+# -
+#
+#   id: 5
+#   oid: 9d178b5f15046343fd32f451df93acc2bdd9e6373be478b968e4cad6b6647351
+#   size: 25
+#   repository_id: 54
+#   created_unix: 1671607299

models/migrations/v1_21/v276.go

@@ -12,6 +12,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	giturl "code.gitea.io/gitea/modules/git/url"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 
 	"xorm.io/xorm"
 )
@@ -163,7 +164,9 @@ func migratePushMirrors(x *xorm.Engine) error {
 
 func getRemoteAddress(ownerName, repoName, remoteName string) (string, error) {
 	repoPath := filepath.Join(setting.RepoRootPath, strings.ToLower(ownerName), strings.ToLower(repoName)+".git")
-
+	if exist, _ := util.IsExist(repoPath); !exist {
+		return "", nil
+	}
 	remoteURL, err := git.GetRemoteAddress(context.Background(), repoPath, remoteName)
 	if err != nil {
 		return "", fmt.Errorf("get remote %s's address of %s/%s failed: %v", remoteName, ownerName, repoName, err)