`git log -G ...` with golang

Question

I want to write a script which is similar to git log -G with go-git

This code prints all commits of the repos, but how to get the added/removed lines of each commit?

package main

import (
    "fmt"
    "os"
    "path/filepath"

    "github.com/go-git/go-git/v5"
    "github.com/go-git/go-git/v5/plumbing/object"
)

func main() {
    if len(os.Args) != 2 {
        fmt.Println("too few arguments. Please specify a directory containing git repos.")
        os.Exit(1)
    }
    err := SearchLog(os.Args[1])
    if err != nil {
        fmt.Println(err)
        os.Exit(1)
    }
}
func SearchLog(dir string) error {
    files, err := os.ReadDir(dir)
    if err != nil {
        return err
    }
    for _, f := range files {
        if f.IsDir() {
            path := filepath.Join(dir, f.Name())
            r, err := git.PlainOpen(path)
            if err != nil {
                fmt.Printf("%s %v", f.Name(), err)
                continue
            }
            err = searchLogInRepo(r)
            if err != nil {
                return err
            }

        }
    }
    return nil
}

func searchLogInRepo(r *git.Repository) error {
    options := git.LogOptions{}
    cIter, err := r.Log(&options)
    if err != nil {
        return err
    }
    err = cIter.ForEach(func(c *object.Commit) error {
        fmt.Println(c)
        return nil
    })
    return err
}

Answer 1

how to get the added/removed lines of each commit?

A git log -G <regex> alone would not show the commit content .

Only a, for instance, git log -p -G would.
And you would need to grep for your searched expression, in order to isolate the differences whose patch text contains added/removed lines that match <regex> .

For each commit, you would need to get the patch from its parent commit (as in plumbing/object/commit_test.go , and look for your regex.