Cannot merge pull request

[badhezi]

Description

Needs feedback
Can't seem to merge a pull request

When creating a simple pull request from the UI and then trying to "create merge commit"
gitea server errors out with below log

Possibly introduced by this commit 69f5ee9

gitea/modules/git/gitcmd/command.go

Line 473 in 03fce8f

panic("stdout and stderr field must be nil when using RunStdBytes")

panics because c.opts.Stdout and c.opts.Stderr and not nil

gitea/modules/git/gitcmd/command.go

Line 471 in 03fce8f

if c.opts.Stdout != nil || c.opts.Stderr != nil {

Debugger shows c.opts.Stdout and c.opts.Stderr are not nil and are initialized to
io.Writer(*strings.Builder) *{addr: *strings.Builder nil, buf: []uint8 len: 0, cap: 0, nil}

Gitea Version

main 03fce8f

Can you reproduce the bug on the Gitea demo site?

No

Log Gist

No response

Screenshots

logs:

2025/10/08 15:42:56 HTTPRequest [W] router: failed    POST /gitea_admin/merge-me/pulls/1/merge for [::1]:57214, panic in 212.7ms @ repo/pull.go:1014(repo.MergePullRequest), err=stdout and stderr field must be nil when using RunStdBytes
2025/10/08 15:42:56 routers/common/errpage.go:25:RenderPanicErrorPage() [E] PANIC: stdout and stderr field must be nil when using RunStdBytes
/usr/local/go/src/runtime/panic.go:783 (0x10090eaff)
        gopanic: fn()
/Users/heziaharon/Documents/repos/gitea/modules/web/routing/logger_manager.go:116 (0x1019792cb)
        (*requestRecordsManager).handler-fm.(*requestRecordsManager).handler.func1.1: panic(localPanicErr)
/usr/local/go/src/runtime/panic.go:783 (0x10090eaff)
        gopanic: fn()
/Users/heziaharon/Documents/repos/gitea/modules/git/gitcmd/command.go:473 (0x101139cf3)
        (*Command).runStdBytes: panic("stdout and stderr field must be nil when using RunStdBytes")
/Users/heziaharon/Documents/repos/gitea/modules/git/gitcmd/command.go:461 (0x1011399cb)
        (*Command).RunStdString: stdoutBytes, stderrBytes, runErr := c.WithParentCallerInfo().runStdBytes(ctx)
/Users/heziaharon/Documents/repos/gitea/services/pull/merge_prepare.go:76 (0x102048387)
        createTemporaryRepoForMerge: trackingCommitID, _, err := mergeCtx.PrepareGitCmd(gitcmd.NewCommand("show-ref", "--hash").AddDynamicArguments(git.BranchPrefix + trackingBranch)).RunStdString(ctx)
/Users/heziaharon/Documents/repos/gitea/services/pull/merge.go:331 (0x102044047)
        doMergeAndPush: mergeCtx, cancel, err := createTemporaryRepoForMerge(ctx, pr, doer, expectedHeadCommitID)
/Users/heziaharon/Documents/repos/gitea/services/pull/merge.go:262 (0x102043853)
        Merge: _, err = doMergeAndPush(ctx, pr, doer, mergeStyle, expectedHeadCommitID, message, repo_module.PushTriggerPRMergeToBase)
/Users/heziaharon/Documents/repos/gitea/routers/web/repo/pull.go:1115 (0x1029938c3)
        MergePullRequest: if err := pull_service.Merge(ctx, pr, ctx.Doer, ctx.Repo.GitRepo, repo_model.MergeStyle(form.Do), form.HeadCommitID, message, false); err != nil {
/usr/local/go/src/reflect/value.go:581 (0x10099508f)
        Value.call: call(frametype, fn, stackArgs, uint32(frametype.Size()), uint32(abid.retOffset), uint32(frameSize), &regArgs)
/usr/local/go/src/reflect/value.go:365 (0x100994563)
        Value.Call: return v.call("Call", in)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:161 (0x101981467)
        toHandlerProvider.func1.1: ret := fn.Call(argsIn)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/chain.go:31 (0x101979b8b)
        (*ChainHandler).ServeHTTP: c.chain.ServeHTTP(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:477 (0x10197c66b)
        (*Mux).routeHTTP: h.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/middleware/get_head.go:37 (0x1029176a7)
        GetHead.func1: next.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:168 (0x1019814bb)
        toHandlerProvider.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/services/context/context.go:210 (0x101ed05b3)
        Contexter.func1.1: next.ServeHTTP(ctx.Resp, ctx.Req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/gitea.com/go-chi/session@v0.0.0-20250926004215-636cadd82e15/session.go:257 (0x10192bc0b)
        Sessioner.func1.1: next.ServeHTTP(w, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:73 (0x10197a663)
        (*Mux).ServeHTTP: mx.handler.ServeHTTP(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:321 (0x10197bc53)
        (*Mux).Mount.func1: handler.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:477 (0x10197c66b)
        (*Mux).routeHTTP: h.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:73 (0x10197a663)
        (*Mux).ServeHTTP: mx.handler.ServeHTTP(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:321 (0x10197bc53)
        (*Mux).Mount.func1: handler.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:477 (0x10197c66b)
        (*Mux).routeHTTP: h.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/routing/logger_manager.go:122 (0x101979187)
        (*requestRecordsManager).handler-fm.(*requestRecordsManager).handler.func1: next.ServeHTTP(w, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/chi-middleware/proxy@v1.1.1/middleware.go:37 (0x10287523b)
        ForwardedHeadersHandler.ForwardedHeaders.func1.1: h.ServeHTTP(w, r)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/routers/common/middleware.go:78 (0x1028774df)
        ProtocolMiddlewares.RequestContextHandler.func2.1: next.ServeHTTP(respWriter, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/routers/common/middleware.go:93 (0x10287713b)
        ProtocolMiddlewares.ChiRoutePathHandler.func1.1: next.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/handler.go:125 (0x101981883)
        toHandlerProvider.wrapHandlerProvider[...].func2.1: h.ServeHTTP(resp, req)
/usr/local/go/src/net/http/server.go:2322 (0x100d72017)
        HandlerFunc.ServeHTTP: f(w, r)
/Users/heziaharon/go/pkg/mod/github.com/go-chi/chi/v5@v5.2.3/mux.go:90 (0x10197a623)
        (*Mux).ServeHTTP: mx.handler.ServeHTTP(w, r)
/Users/heziaharon/Documents/repos/gitea/modules/web/router.go:243 (0x10198306b)
        (*Router).normalizeRequestPath: next.ServeHTTP(resp, req)
/Users/heziaharon/Documents/repos/gitea/modules/web/router.go:181 (0x101982b6f)
        (*Router).ServeHTTP: r.normalizeRequestPath(w, req, r.chiRouter)
/usr/local/go/src/net/http/server.go:3340 (0x100d8f1ff)
        serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
/usr/local/go/src/net/http/server.go:2109 (0x100d70407)
        (*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
/usr/local/go/src/runtime/asm_arm64.s:1268 (0x100917503)
        goexit: MOVD    R0, R0  // NOP

Git Version

2.39.5

Operating System

macos

How are you running Gitea?

Local setup make watch

Database

PostgreSQL

[badhezi]

FYI setting stdout and stderr to nil instead of an empty builder resolves the issue
Before:

func (ctx *mergeContext) PrepareGitCmd(cmd *gitcmd.Command) *gitcmd.Command {
	ctx.outbuf.Reset()
	ctx.errbuf.Reset()
	return cmd.WithEnv(ctx.env).
		WithDir(ctx.tmpBasePath).
		WithParentCallerInfo().
		WithStdout(ctx.outbuf).
		WithStderr(ctx.errbuf)
}

After:

func (ctx *mergeContext) PrepareGitCmd(cmd *gitcmd.Command) *gitcmd.Command {
	ctx.outbuf.Reset()
	ctx.errbuf.Reset()
	return cmd.WithEnv(ctx.env).
		WithDir(ctx.tmpBasePath).
		WithParentCallerInfo().
		WithStdout(nil).
		WithStderr(nil)
}

I'm just not sure what are the other implications of this perhaps @lunny can help, other commands run fine as PrepareGitCmd is only called in merge flows, it seems.

it stems from using WithStdout() or WithStderr() set to an empty io.Writer and then the command is called from RunStdString() or RunStdBytes()

Edit:
The test case at

gitea/tests/integration/pull_merge_test.go

Line 46 in 03fce8f

func testPullMerge(t *testing.T, session *TestSession, user, repo, pullnum string, mergeStyle repo_model.MergeStyle, deleteBranch bool) *httptest.ResponseRecorder {

does not fail because it is required to supply the request form with head_commit_id which will take us to

	if expectedHeadCommitID != "" {
		trackingCommitID, _, err := mergeCtx.PrepareGitCmd(gitcmd.NewCommand("show-ref", "--hash").AddDynamicArguments(git.BranchPrefix + trackingBranch)).RunStdString(ctx)

it's included when calling merge from the UI but not from this test case.