Gitea/modules/gitrepo/compare.go

// Copyright 2025 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package gitrepo

import (
	"context"
	"fmt"
	"strconv"
	"strings"

	"code.gitea.io/gitea/modules/git/gitcmd"
)

// DivergeObject represents commit count diverging commits
type DivergeObject struct {
	Ahead  int
	Behind int
}

// GetDivergingCommits returns the number of commits a targetBranch is ahead or behind a baseBranch
func GetDivergingCommits(ctx context.Context, repo Repository, baseBranch, targetBranch string) (*DivergeObject, error) {
	cmd := gitcmd.NewCommand("rev-list", "--count", "--left-right").
		AddDynamicArguments(baseBranch + "..." + targetBranch).AddArguments("--")
	stdout, _, err1 := cmd.RunStdString(ctx, &gitcmd.RunOpts{Dir: repoPath(repo)})
	if err1 != nil {
		return nil, err1
	}

	left, right, found := strings.Cut(strings.Trim(stdout, "\n"), "\t")
	if !found {
		return nil, fmt.Errorf("git rev-list output is missing a tab: %q", stdout)
	}

	behind, err := strconv.Atoi(left)
	if err != nil {
		return nil, err
	}
	ahead, err := strconv.Atoi(right)
	if err != nil {
		return nil, err
	}
	return &DivergeObject{Ahead: ahead, Behind: behind}, nil
}