fix: git cache (#38763)

1. always use "last commit cache"
2. correctly build the cache key for any input (SafeCacheKey)
3. fix the git note "last commit cache FIXME" and avoid OOM

modules/git/git.go

@@ -13,6 +13,7 @@ import (
 	"runtime"
 	"strings"
 
+	"gitea.dev/modules/cache"
 	"gitea.dev/modules/git/gitcmd"
 	"gitea.dev/modules/globallock"
 	"gitea.dev/modules/log"
@@ -191,6 +192,7 @@ func RunGitTests(m interface{ Run() int }) {
 }
 
 func runGitTests(m interface{ Run() int }) int {
+	_ = cache.Init()
 	gitHomePath, cleanup, err := tempdir.OsTempDir("gitea-test").MkdirTempRandom("git-home")
 	if err != nil {
 		return testlogger.MainErrorf("unable to create temp dir: %v", err)