github__gh-stack/internal/git/gitops.go

package git

import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

// RebaseOpts holds optional parameters for git rebase operations.
type RebaseOpts struct {
	CommitterDateIsAuthorDate bool
}

// ErrRemoteBranchNotFound indicates that a requested branch does not exist on
// the remote. It is distinct from transport, authentication, and other fetch
// failures.
var ErrRemoteBranchNotFound = errors.New("remote branch not found")

// Ops defines the interface for git operations used by commands.
// The package-level functions are the default production implementation.
// Tests can substitute a mock via SetOps().
type Ops interface {
	GitDir() (string, error)
	RootDir() (string, error)
	CurrentBranch() (string, error)
	BranchExists(name string) bool
	RemoteTrackingRefs(branch string) ([]string, error)
	CheckoutBranch(name string) error
	Fetch(remote string) error
	FetchBranch(remote, branch string) error
	FetchBranches(remote string, branches []string) error
	DefaultBranch() (string, error)
	CreateBranch(name, base string) error
	Push(remote string, branches []string, force, atomic bool) error
	ResolveRemote(branch string) (string, error)
	Rebase(base string, opts RebaseOpts) error
	EnableRerere() error
	IsRerereEnabled() (bool, error)
	IsRerereDeclined() (bool, error)
	SaveRerereDeclined() error
	GetSavedRemote() (string, error)
	SaveRemote(remote string) error
	ClearRemote() error
	RebaseOnto(newBase, oldBase, branch string, opts RebaseOpts) error
	RebaseContinue(opts RebaseOpts) error
	RebaseAbort() error
	IsRebaseInProgress() bool
	ConflictedFiles() ([]string, error)
	FindConflictMarkers(filePath string) (*ConflictMarkerInfo, error)
	IsAncestor(ancestor, descendant string) (bool, error)
	RevParse(ref string) (string, error)
	RevParseMulti(refs []string) ([]string, error)
	MergeBase(a, b string) (string, error)
	MergeBaseForkPoint(ref, branch string) (string, error)
	Log(ref string, maxCount int) ([]CommitInfo, error)
	LogRange(base, head string) ([]CommitInfo, error)
	DiffStatRange(base, head string) (additions, deletions int, err error)
	DiffStatFiles(base, head string) ([]FileDiffStat, error)
	DeleteBranch(name string, force bool) error
	DeleteRemoteBranch(remote, branch string) error
	DeleteTrackingRef(remote, branch string) error
	ResetHard(ref string) error
	SetUpstreamTracking(branch, remote string) error
	UpstreamRemote(branch string) (string, error)
	MergeFF(target string) error
	UpdateBranchRef(branch, sha string) error
	StageAll() error
	StageTracked() error
	HasStagedChanges() bool
	Commit(message string) (string, error)
	CommitInteractive() (string, error)
	ValidateRefName(name string) error
	RenameBranch(oldName, newName string) error
	CherryPick(commits []string) error
	CherryPickQuit() error
	CherryPickAbort() error
	CherryPickContinue() error
	IsCherryPickInProgress() bool
	HasUncommittedChanges() (bool, error)
	LogMerges(base, head string) ([]CommitInfo, error)
}

// defaultOps implements Ops by delegating to the real git client and helpers.
type defaultOps struct{}

var _ Ops = (*defaultOps)(nil)

// ops is the current implementation. Tests replace this via SetOps().
var ops Ops = &defaultOps{}

// SetOps replaces the git operations implementation. Returns a restore function.
func SetOps(o Ops) func() {
	old := ops
	ops = o
	return func() { ops = old }
}

// CurrentOps returns the current Ops implementation.
func CurrentOps() Ops {
	return ops
}

// --- defaultOps method implementations ---

func (d *defaultOps) GitDir() (string, error) {
	return client.GitDir(context.Background())
}

func (d *defaultOps) RootDir() (string, error) {
	return run("rev-parse", "--show-toplevel")
}

func (d *defaultOps) CurrentBranch() (string, error) {
	return client.CurrentBranch(context.Background())
}

func (d *defaultOps) BranchExists(name string) bool {
	return client.HasLocalBranch(context.Background(), name)
}

func (d *defaultOps) RemoteTrackingRefs(branch string) ([]string, error) {
	remoteOutput, err := run("remote")
	if err != nil {
		return nil, fmt.Errorf("listing remotes: %w", err)
	}
	remotes := strings.Fields(remoteOutput)
	if len(remotes) == 0 {
		return nil, nil
	}

	refOutput, err := run("for-each-ref", "--format=%(refname)", "refs/remotes/")
	if err != nil {
		return nil, fmt.Errorf("listing remote-tracking refs: %w", err)
	}
	available := make(map[string]struct{})
	for _, ref := range strings.Fields(refOutput) {
		available[ref] = struct{}{}
	}

	var matches []string
	for _, remote := range remotes {
		ref := fmt.Sprintf("refs/remotes/%s/%s", remote, branch)
		if _, ok := available[ref]; ok {
			matches = append(matches, ref)
		}
	}
	return matches, nil
}

func (d *defaultOps) CheckoutBranch(name string) error {
	return client.CheckoutBranch(context.Background(), name)
}

func (d *defaultOps) Fetch(remote string) error {
	return client.Fetch(context.Background(), remote, "")
}

func (d *defaultOps) FetchBranch(remote, branch string) error {
	refspec := fmt.Sprintf("+refs/heads/%s:refs/remotes/%s/%s", branch, remote, branch)
	if err := runSilent("fetch", remote, refspec); err != nil {
		if isMissingRemoteRefError(err) {
			return fmt.Errorf("%w: %s/%s", ErrRemoteBranchNotFound, remote, branch)
		}
		return err
	}
	return nil
}

func (d *defaultOps) FetchBranches(remote string, branches []string) error {
	if len(branches) == 0 {
		return nil
	}
	// Build explicit refspecs that create/update tracking refs for every
	// branch, regardless of whether a tracking ref already exists.
	// The + prefix allows non-fast-forward tracking-ref updates.
	refspecs := make([]string, len(branches))
	for i, b := range branches {
		refspecs[i] = fmt.Sprintf("+refs/heads/%s:refs/remotes/%s/%s", b, remote, b)
	}
	// Fast path: fetch all branches in a single call.
	args := []string{"fetch", remote}
	args = append(args, refspecs...)
	if err := runSilent(args...); err == nil {
		return nil
	}
	// Fallback: one branch may be absent on the remote or deleted since
	// the last fetch. Fetch individually so one missing branch doesn't
	// block the rest, while still surfacing real fetch failures.
	var fetchErr error
	for _, rs := range refspecs {
		err := runSilent("fetch", remote, rs)
		if err == nil || isMissingRemoteRefError(err) {
			continue
		}
		if fetchErr == nil {
			fetchErr = fmt.Errorf("fetching from %s: %w", remote, err)
		}
	}
	return fetchErr
}

func isMissingRemoteRefError(err error) bool {
	return err != nil && strings.Contains(err.Error(), "couldn't find remote ref")
}

func (d *defaultOps) DefaultBranch() (string, error) {
	ref, err := run("symbolic-ref", "refs/remotes/origin/HEAD")
	if err != nil {
		for _, name := range []string{"main", "master"} {
			if BranchExists(name) {
				return name, nil
			}
		}
		return "", err
	}
	return strings.TrimPrefix(ref, "refs/remotes/origin/"), nil
}

func (d *defaultOps) CreateBranch(name, base string) error {
	return runSilent("branch", name, base)
}

func (d *defaultOps) Push(remote string, branches []string, force, atomic bool) error {
	args := []string{"push", remote}
	if force {
		// Build explicit per-branch leases and refspecs. This removes
		// dependence on push.default / upstream configuration and
		// ensures correct lease values for branches whose tracking ref
		// was missing before the preceding FetchBranches call.
		for _, b := range branches {
			trackingRef := fmt.Sprintf("refs/remotes/%s/%s", remote, b)
			sha, err := run("rev-parse", "--verify", "--quiet", trackingRef)
			if err == nil && sha != "" {
				// Tracking ref exists: lease against the known SHA.
				args = append(args, fmt.Sprintf("--force-with-lease=refs/heads/%s:%s", b, sha))
			} else {
				// No tracking ref: branch is absent on remote (never
				// pushed). Empty expected value means "must not exist".
				args = append(args, fmt.Sprintf("--force-with-lease=refs/heads/%s:", b))
			}
		}
	}
	if atomic {
		args = append(args, "--atomic")
	}
	// Fully-qualified refspecs: refs/heads/<local>:refs/heads/<remote>.
	// Qualifying the source (not a bare branch name) ensures a branch name is
	// never reinterpreted as refspec syntax — e.g. a leading "+" is part of the
	// ref, not a force modifier. This form is identical whether or not the push
	// is forced; force is supplied out-of-band by the --force-with-lease flags
	// built above.
	for _, b := range branches {
		args = append(args, fmt.Sprintf("refs/heads/%s:refs/heads/%s", b, b))
	}
	return runSilent(args...)
}

// ResolveRemote determines the remote for pushing a branch. It checks git
// config keys in priority order (branch.<name>.pushRemote, remote.pushDefault,
// branch.<name>.remote), then checks the gh-stack.remote saved preference,
// then falls back to listing all remotes. If exactly one remote exists it is
// returned. If multiple exist, ErrMultipleRemotes is returned with the list
// attached. If none exist, a plain error is returned.
func (d *defaultOps) ResolveRemote(branch string) (string, error) {
	candidates := []string{
		"branch." + branch + ".pushRemote",
		"remote.pushDefault",
		"branch." + branch + ".remote",
	}
	for _, key := range candidates {
		out, err := run("config", "--get", key)
		if err == nil && out != "" {
			return out, nil
		}
	}

	// Check gh-stack saved remote preference.
	if saved, err := d.GetSavedRemote(); err == nil && saved != "" {
		return saved, nil
	}

	out, err := run("remote")
	if err != nil {
		return "", fmt.Errorf("could not list remotes: %w", err)
	}
	remotes := strings.Fields(strings.TrimSpace(out))
	if len(remotes) == 1 {
		return remotes[0], nil
	}
	if len(remotes) > 1 {
		return "", &ErrMultipleRemotes{Remotes: remotes}
	}
	return "", fmt.Errorf("no remotes configured")
}

func (d *defaultOps) Rebase(base string, opts RebaseOpts) error {
	args := []string{"rebase"}
	if opts.CommitterDateIsAuthorDate {
		args = append(args, "--committer-date-is-author-date")
	}
	args = append(args, base)
	return runRebaseCommand(args, opts)
}

func (d *defaultOps) EnableRerere() error {
	if err := runSilent("config", "rerere.enabled", "true"); err != nil {
		return err
	}
	return runSilent("config", "rerere.autoupdate", "true")
}

func (d *defaultOps) IsRerereEnabled() (bool, error) {
	out, err := run("config", "--get", "rerere.enabled")
	if err != nil {
		// Missing key — not enabled.
		return false, nil
	}
	return strings.EqualFold(strings.TrimSpace(out), "true"), nil
}

func (d *defaultOps) IsRerereDeclined() (bool, error) {
	out, err := run("config", "--get", "gh-stack.rerere-declined")
	if err != nil {
		return false, nil
	}
	return strings.EqualFold(strings.TrimSpace(out), "true"), nil
}

func (d *defaultOps) SaveRerereDeclined() error {
	return runSilent("config", "gh-stack.rerere-declined", "true")
}

func (d *defaultOps) GetSavedRemote() (string, error) {
	out, err := run("config", "--get", "gh-stack.remote")
	if err != nil {
		return "", err
	}
	return out, nil
}

func (d *defaultOps) SaveRemote(remote string) error {
	return runSilent("config", "gh-stack.remote", remote)
}

func (d *defaultOps) ClearRemote() error {
	return runSilent("config", "--unset", "gh-stack.remote")
}

func (d *defaultOps) RebaseOnto(newBase, oldBase, branch string, opts RebaseOpts) error {
	args := []string{"rebase"}
	if opts.CommitterDateIsAuthorDate {
		args = append(args, "--committer-date-is-author-date")
	}
	args = append(args, "--onto", newBase, oldBase, branch)
	return runRebaseCommand(args, opts)
}

func (d *defaultOps) RebaseContinue(opts RebaseOpts) error {
	err := rebaseContinueOnce(opts)
	if err == nil {
		return nil
	}
	return tryAutoResolveRebase(err, opts)
}

func (d *defaultOps) RebaseAbort() error {
	return runSilent("rebase", "--abort")
}

func (d *defaultOps) IsRebaseInProgress() bool {
	gitDir, err := GitDir()
	if err != nil {
		return false
	}
	for _, dir := range []string{"rebase-merge", "rebase-apply"} {
		rebasePath := filepath.Join(gitDir, dir)
		if info, err := os.Stat(rebasePath); err == nil && info.IsDir() {
			return true
		}
	}
	return false
}

func (d *defaultOps) ConflictedFiles() ([]string, error) {
	output, err := run("diff", "--name-only", "--diff-filter=U")
	if err != nil {
		return nil, err
	}
	if output == "" {
		return nil, nil
	}
	return strings.Split(output, "\n"), nil
}

func (d *defaultOps) FindConflictMarkers(filePath string) (*ConflictMarkerInfo, error) {
	output, err := run("diff", "--check", "--", filePath)
	if output == "" && err != nil {
		return nil, err
	}

	info := &ConflictMarkerInfo{File: filePath}
	var currentSection *ConflictSection

	for _, line := range strings.Split(output, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		parts := strings.SplitN(line, ":", 3)
		if len(parts) < 3 {
			continue
		}
		lineNo, parseErr := strconv.Atoi(strings.TrimSpace(parts[1]))
		if parseErr != nil {
			continue
		}
		marker := strings.TrimSpace(parts[2])
		if strings.Contains(marker, "leftover conflict marker") {
			if currentSection == nil || currentSection.EndLine != 0 {
				currentSection = &ConflictSection{StartLine: lineNo}
				info.Sections = append(info.Sections, *currentSection)
			}
			info.Sections[len(info.Sections)-1].EndLine = lineNo
		}
	}

	return info, nil
}

func (d *defaultOps) IsAncestor(ancestor, descendant string) (bool, error) {
	err := runSilent("merge-base", "--is-ancestor", ancestor, descendant)
	if err == nil {
		return true, nil
	}
	var exitErr *exec.ExitError
	if errors.As(err, &exitErr) && exitErr.ExitCode() == 1 {
		return false, nil
	}
	return false, err
}

func (d *defaultOps) RevParse(ref string) (string, error) {
	return run("rev-parse", ref)
}

func (d *defaultOps) RevParseMulti(refs []string) ([]string, error) {
	if len(refs) == 0 {
		return nil, nil
	}
	args := append([]string{"rev-parse"}, refs...)
	out, err := run(args...)
	if err != nil {
		return nil, err
	}
	shas := strings.Split(out, "\n")
	if len(shas) != len(refs) {
		return nil, fmt.Errorf("rev-parse returned %d SHAs for %d refs", len(shas), len(refs))
	}
	return shas, nil
}

func (d *defaultOps) MergeBase(a, b string) (string, error) {
	return run("merge-base", a, b)
}

func (d *defaultOps) MergeBaseForkPoint(ref, branch string) (string, error) {
	return run("merge-base", "--fork-point", ref, branch)
}

func (d *defaultOps) Log(ref string, maxCount int) ([]CommitInfo, error) {
	format := "%H\t%s\t%at"
	output, err := run("log", ref, "--format="+format, "-n", strconv.Itoa(maxCount))
	if err != nil {
		return nil, err
	}
	if output == "" {
		return nil, nil
	}

	var commits []CommitInfo
	for _, line := range strings.Split(output, "\n") {
		parts := strings.SplitN(line, "\t", 3)
		if len(parts) < 3 {
			continue
		}
		ts, _ := strconv.ParseInt(parts[2], 10, 64)
		commits = append(commits, CommitInfo{
			SHA:     parts[0],
			Subject: parts[1],
			Time:    time.Unix(ts, 0),
		})
	}
	return commits, nil
}

func (d *defaultOps) LogRange(base, head string) ([]CommitInfo, error) {
	format := "%H%x01%B%x01%at%x00"
	rangeSpec := base + ".." + head
	output, err := run("log", rangeSpec, "--format="+format)
	if err != nil {
		return nil, err
	}
	if output == "" {
		return nil, nil
	}

	var commits []CommitInfo
	for _, record := range strings.Split(output, "\x00") {
		record = strings.TrimSpace(record)
		if record == "" {
			continue
		}
		parts := strings.SplitN(record, "\x01", 3)
		if len(parts) < 3 {
			continue
		}
		ts, _ := strconv.ParseInt(strings.TrimSpace(parts[2]), 10, 64)
		subject, body := splitCommitMessage(parts[1])
		commits = append(commits, CommitInfo{
			SHA:     parts[0],
			Subject: subject,
			Body:    body,
			Time:    time.Unix(ts, 0),
		})
	}
	return commits, nil
}

// splitCommitMessage splits a full commit message into subject (first line)
// and body (remaining lines with leading/trailing blank lines trimmed).
func splitCommitMessage(msg string) (subject, body string) {
	msg = strings.TrimSpace(msg)
	if i := strings.IndexByte(msg, '\n'); i >= 0 {
		subject = msg[:i]
		body = strings.TrimSpace(msg[i+1:])
	} else {
		subject = msg
	}
	return
}

func (d *defaultOps) DiffStatRange(base, head string) (additions, deletions int, err error) {
	output, err := run("diff", "--numstat", base+".."+head)
	if err != nil {
		return 0, 0, err
	}
	if output == "" {
		return 0, 0, nil
	}
	for _, line := range strings.Split(output, "\n") {
		parts := strings.Fields(line)
		if len(parts) < 2 {
			continue
		}
		if parts[0] == "-" {
			continue
		}
		a, _ := strconv.Atoi(parts[0])
		d, _ := strconv.Atoi(parts[1])
		additions += a
		deletions += d
	}
	return additions, deletions, nil
}

func (d *defaultOps) DiffStatFiles(base, head string) ([]FileDiffStat, error) {
	output, err := run("diff", "--numstat", base+".."+head)
	if err != nil {
		return nil, err
	}
	if output == "" {
		return nil, nil
	}
	var files []FileDiffStat
	for _, line := range strings.Split(output, "\n") {
		parts := strings.Fields(line)
		if len(parts) < 3 {
			continue
		}
		a, _ := strconv.Atoi(parts[0])
		d, _ := strconv.Atoi(parts[1])
		files = append(files, FileDiffStat{
			Path:      parts[2],
			Additions: a,
			Deletions: d,
		})
	}
	return files, nil
}

func (d *defaultOps) DeleteBranch(name string, force bool) error {
	flag := "-d"
	if force {
		flag = "-D"
	}
	return runSilent("branch", flag, name)
}

func (d *defaultOps) DeleteRemoteBranch(remote, branch string) error {
	// Fully-qualify the ref so a branch name is never reinterpreted as
	// refspec syntax.
	return runSilent("push", remote, "--delete", "refs/heads/"+branch)
}

func (d *defaultOps) DeleteTrackingRef(remote, branch string) error {
	return runSilent("branch", "-dr", remote+"/"+branch)
}

func (d *defaultOps) ResetHard(ref string) error {
	return runSilent("reset", "--hard", ref)
}

func (d *defaultOps) SetUpstreamTracking(branch, remote string) error {
	return runSilent("branch", "--set-upstream-to="+remote+"/"+branch, branch)
}

func (d *defaultOps) UpstreamRemote(branch string) (string, error) {
	return run("config", "--get", "branch."+branch+".remote")
}

func (d *defaultOps) MergeFF(target string) error {
	return runSilent("merge", "--ff-only", target)
}

func (d *defaultOps) UpdateBranchRef(branch, sha string) error {
	return runSilent("branch", "-f", branch, sha)
}

func (d *defaultOps) StageAll() error {
	return runSilent("add", "-A")
}

func (d *defaultOps) StageTracked() error {
	return runSilent("add", "-u")
}

func (d *defaultOps) HasStagedChanges() bool {
	err := runSilent("diff", "--cached", "--quiet")
	return err != nil
}

func (d *defaultOps) Commit(message string) (string, error) {
	if err := runSilent("commit", "-m", message); err != nil {
		return "", err
	}
	return run("rev-parse", "HEAD")
}

// CommitInteractive launches the user's editor for the commit message.
func (d *defaultOps) CommitInteractive() (string, error) {
	if err := runInteractive("commit"); err != nil {
		return "", err
	}
	return run("rev-parse", "HEAD")
}

func (d *defaultOps) ValidateRefName(name string) error {
	_, err := run("check-ref-format", "--branch", name)
	return err
}

func (d *defaultOps) RenameBranch(oldName, newName string) error {
	return runSilent("branch", "-m", oldName, newName)
}

func (d *defaultOps) CherryPick(commits []string) error {
	args := append([]string{"cherry-pick"}, commits...)
	return runSilent(args...)
}

// CherryPickQuit clears the in-progress cherry-pick sequencer state without
// touching the working tree or index (git cherry-pick --quit). Used to clear
// any stale sequencer state before starting a fresh cherry-pick.
func (d *defaultOps) CherryPickQuit() error {
	return runSilent("cherry-pick", "--quit")
}

// CherryPickAbort cancels an in-progress cherry-pick and restores the working
// tree and index to the state before the cherry-pick began
// (git cherry-pick --abort). Errors if no cherry-pick is in progress, so
// callers should gate this with IsCherryPickInProgress.
func (d *defaultOps) CherryPickAbort() error {
	return runSilent("cherry-pick", "--abort")
}

func (d *defaultOps) CherryPickContinue() error {
	cmd := exec.Command("git", "cherry-pick", "--continue")
	cmd.Env = append(os.Environ(), "GIT_EDITOR=true")
	return cmd.Run()
}

// IsCherryPickInProgress reports whether a cherry-pick is currently in progress
// by checking for the CHERRY_PICK_HEAD marker in the git directory.
func (d *defaultOps) IsCherryPickInProgress() bool {
	gitDir, err := GitDir()
	if err != nil {
		return false
	}
	if _, err := os.Stat(filepath.Join(gitDir, "CHERRY_PICK_HEAD")); err == nil {
		return true
	}
	return false
}

func (d *defaultOps) HasUncommittedChanges() (bool, error) {
	out, err := run("status", "--porcelain")
	if err != nil {
		return false, err
	}
	return out != "", nil
}

func (d *defaultOps) LogMerges(base, head string) ([]CommitInfo, error) {
	format := "%H%x01%B%x01%at%x00"
	rangeSpec := base + ".." + head
	output, err := run("log", "--merges", rangeSpec, "--format="+format)
	if err != nil {
		return nil, err
	}
	if output == "" {
		return nil, nil
	}

	var commits []CommitInfo
	for _, record := range strings.Split(output, "\x00") {
		record = strings.TrimSpace(record)
		if record == "" {
			continue
		}
		parts := strings.SplitN(record, "\x01", 3)
		if len(parts) < 3 {
			continue
		}
		ts, _ := strconv.ParseInt(strings.TrimSpace(parts[2]), 10, 64)
		subject, body := splitCommitMessage(parts[1])
		commits = append(commits, CommitInfo{
			SHA:     parts[0],
			Subject: subject,
			Body:    body,
			Time:    time.Unix(ts, 0),
		})
	}
	return commits, nil
}