Refactor CatFile batch implementation and introduce batch-command for git 2.36

[lunny]

For git version 2.36, git cat-file --batch-command was introduced which can replace git cat-file --batch and git cat-file --batch-check.

This PR implements an abstract layer for the batch commands so that both git 2.36 and lower version git can work.
If git version is lower than 2.36, it will start two subprocesses git cat-file --batch and git cat-file --batch-check.
If git version is greater than 2.36, only git cat-file --batch-command will be started.

This reduced half of child processes of git catfiles.

[lunny]

It's ready to review again.

[wxiaoguang]

Saw many flaky tests:

--- FAIL: TestPullCreate (0.71s)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed GET /user/login for test-mock:12345, 200 OK in 7.8ms @ auth/auth.go:184(auth.SignIn)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed POST /user/login for test-mock:12345, 303 See Other in 9.8ms @ auth/auth.go:197(auth.SignInPost)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed GET /user1/repo1 for test-mock:12345, 404 Not Found in 3.4ms @ context/repo.go:417(context.RepoAssignment)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed GET /user2/repo1 for test-mock:12345, 200 OK in 86.0ms @ repo/view_home.go:367(repo.Home)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed GET /user2/repo1/fork for test-mock:12345, 200 OK in 27.3ms @ repo/fork.go:126(repo.Fork)
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed POST /user2/repo1/fork for test-mock:12345, 500 Internal Server Error in 22.5ms @ repo/fork.go:137(repo.ForkPost)
    repo_fork_test.go:54: Response length:  2439
    repo_fork_test.go:54: 
        	Error Trace:	/home/runner/work/gitea/gitea/tests/integration/integration_test.go:354
        	            				/home/runner/work/gitea/gitea/tests/integration/integration_test.go:160
        	            				/home/runner/work/gitea/gitea/tests/integration/repo_fork_test.go:54
        	            				/home/runner/work/gitea/gitea/tests/integration/pull_create_test.go:138
        	            				/home/runner/work/gitea/gitea/tests/integration/git_helper_for_declarative_test.go:88
        	            				/home/runner/work/gitea/gitea/tests/integration/pull_create_test.go:136
        	Error:      	Not equal: 
        	            	expected: 200
        	            	actual  : 500
        	Test:       	TestPullCreate
        	Messages:   	Request: POST /user2/repo1/fork
    testlogger.go:134: Flushing queues failed with error context canceled
=== TestPullCreate_TitleEscape (tests/integration/pull_create_test.go:164)
--- FAIL: TestPullCreate_TitleEscape (0.64s)
    git_helper_for_declarative_test.go:62: 
        	Error Trace:	/home/runner/work/gitea/gitea/tests/test_utils.go:236
        	            				/home/runner/work/gitea/gitea/tests/integration/git_helper_for_declarative_test.go:62
        	            				/home/runner/work/gitea/gitea/tests/integration/pull_create_test.go:164
        	Error:      	Received unexpected error:
        	            	failed to generate sequence update: context canceled
        	Test:       	TestPullCreate_TitleEscape
    testlogger.go:61: 2025/10/27 00:39:18 HTTPRequest [I] router: completed GET /user/login for test-mock:12345, 200 OK in 8.0ms @ auth/auth.go:184(auth.SignIn)
    testlogger.go:61: 2025/10/27 00:39:19 HTTPRequest [I] router: completed POST /user/login for test-mock:12345, 303 See Other in 10.1ms @ auth/auth.go:197(auth.SignInPost)
    testlogger.go:61: 2025/10/27 00:39:19 HTTPRequest [I] router: completed GET /user1/repo1 for test-mock:12345, 404 Not Found in 4.0ms @ context/repo.go:417(context.RepoAssignment)
    testlogger.go:61: 2025/10/27 00:39:19 HTTPRequest [I] router: completed GET /user2/repo1 for test-mock:12345, 200 OK in 86.5ms @ repo/view_home.go:367(repo.Home)
    testlogger.go:61: 2025/10/27 00:39:19 HTTPRequest [I] router: completed GET /user2/repo1/fork for test-mock:12345, 200 OK in 31.8ms @ repo/fork.go:126(repo.Fork)
    testlogger.go:61: 2025/10/27 00:39:19 HTTPRequest [I] router: completed POST /user2/repo1/fork for test-mock:12345, 500 Internal Server Error in 27.8ms @ repo/fork.go:137(repo.ForkPost)
    repo_fork_test.go:54: Response length:  2439
    repo_fork_test.go:54: 
        	Error Trace:	/home/runner/work/gitea/gitea/tests/integration/integration_test.go:354
        	            				/home/runner/work/gitea/gitea/tests/integration/integration_test.go:160
        	            				/home/runner/work/gitea/gitea/tests/integration/repo_fork_test.go:54
        	            				/home/runner/work/gitea/gitea/tests/integration/pull_create_test.go:166
        	            				/home/runner/work/gitea/gitea/tests/integration/git_helper_for_declarative_test.go:88
        	            				/home/runner/work/gitea/gitea/tests/integration/pull_create_test.go:164
        	Error:      	Not equal: 
        	            	expected: 200
        	            	actual  : 500
        	Test:       	TestPullCreate_TitleEscape
        	Messages:   	Request: POST /user2/repo1/fork
    testlogger.go:134: Flushing queues failed with error context canceled
=== TestPullBranchDelete (tests/integration/pull_create_test.go:226)

---

=== TestAPIChangeFiles (tests/integration/api_repo_files_change_test.go:63)
	/home/runner/go/pkg/mod/github.com/syndtr/[email protected]/leveldb/db.go:142 +0x447
goroutine 692 [select]:
github.com/syndtr/goleveldb/leveldb/util.(*BufferPool).drain(0xc002960620)
	/home/runner/go/pkg/mod/github.com/syndtr/[email protected]/leveldb/util/buffer_pool.go:206 +0xc8
created by github.com/syndtr/goleveldb/leveldb/util.NewBufferPool in goroutine 691
	/home/runner/go/pkg/mod/github.com/syndtr/[email protected]/leveldb/util/buffer_pool.go:237 +0x17a
goroutine 1179514 [sync.WaitGroup.Wait, 10 minutes]:
sync.runtime_SemacquireWaitGroup(0xc0047158c0?, 0x0?)
	/opt/hostedtoolcache/go/1.25.3/x64/src/runtime/sema.go:114 +0x2e
sync.(*WaitGroup).Wait(0xc001f30320)
	/opt/hostedtoolcache/go/1.25.3/x64/src/sync/waitgroup.go:206 +0x85
code.gitea.io/gitea/tests/integration.TestRepoCommitsStatusParallel(0xc0085fddc0)
	/home/runner/work/gitea/gitea/tests/integration/repo_commits_test.go:208 +0x2aa
testing.tRunner(0xc0085fddc0, 0x40e0668)
	/opt/hostedtoolcache/go/1.25.3/x64/src/testing/testing.go:1934 +0xea
created by testing.(*T).Run in goroutine 1
	/opt/hostedtoolcache/go/1.25.3/x64/src/testing/testing.go:1997 +0x465
goroutine 653866 [select, 16 minutes]:
code.gitea.io/gitea/modules/log.(*EventWriterBaseImpl).Run(0xc00806b860, {0x457a4f8, 0xc0040b94c0})
	/home/runner/work/gitea/gitea/modules/log/event_writer_base.go:81 +0x279
code.gitea.io/gitea/modules/log.eventWriterStartGo.func1()
	/home/runner/work/gitea/gitea/modules/log/event_writer_base.go:157 +0xa5
created by code.gitea.io/gitea/modules/log.eventWriterStartGo in goroutine 653864
	/home/runner/work/gitea/gitea/modules/log/event_writer_base.go:153 +0x191

[wxiaoguang]

No easy fix unless rewrite more legacy code

Do you have the determination to continue.

// FIXME: for debugging purpose only
// At the moment, the old logic (debugTestAlwaysNewBatch=false: reuse the existing batch if not in use)
// causes random test failures: it makes the `t.Context()` occasionally canceled with unknown reasons.
// In theory, the `t.Context()` should never be affected by testing code and can never be canceled, but it does happen.
// The stranger thing is that the failure tests are almost around TestAPIPullUpdateByRebase,
// it almost are during MSSQL testing, sometimes PGSQL, never others.

[wxiaoguang]

Give up. Old branch is saved at https://github.com/lunny/gitea/tree/lunny/catfile_batch_refactor-old , but it can't be merged because there are unclear random CI failures.

Even I have rewritten from scratch by a simpler approach, the unclear random failure still exists.

I have traced down the problem to GetRefCommitID. If we force it to always use a new --batch process (but not reuse the previous created one), then CI can always succeed. However:

1. Keep creating new process for GetRefCommitID is not right.
2. Don't know the root cause, no clue what happens.