Implement MVP merge logic (#2)

What?
- Add default cobra CLI project structure
- Implement bare minimum logic to merge repos into the current working
directory using:
  - https://jeffkreeftmeijer.com/git-combine/
  - https://alexharv074.github.io/puppet/2017/10/04/merge-a-git-repository-and-its-history-into-a-subdirectory-of-a-second-git-repository.html

Notes
- Does not currently support merging local repos, or remotes pulled from
a non SSH remote.
- Documentation has not been added yet

cmd/root.go

@@ -0,0 +1,19 @@
+package cmd
+
+import (
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+var rootCmd = &cobra.Command{
+	Use:   "many2mono",
+	Short: "TBD",
+}
+
+func Execute() {
+	err := rootCmd.Execute()
+	if err != nil {
+		os.Exit(1)
+	}
+}

cmd/run.go

@@ -0,0 +1,72 @@
+package cmd
+
+import (
+	"log"
+	"strings"
+
+	"github.com/oliverhohn/many2mono/helper"
+	"github.com/oliverhohn/many2mono/model"
+	"github.com/spf13/cobra"
+)
+
+// CLI flags
+var defaultBranch string
+var dryRun bool
+
+var runCmd = &cobra.Command{
+	Use:   "run",
+	Short: "TBD",
+	Args:  cobra.MatchAll(cobra.MinimumNArgs(1)),
+	Run: func(cmd *cobra.Command, args []string) {
+		repos := []*model.Repo{}
+		for _, path := range args {
+			r, err := model.NewRepo(path)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			repos = append(repos, r)
+		}
+
+		if duplicateRepos := findDuplicateRepoNames(repos); len(duplicateRepos) > 0 {
+			log.Fatalf("Cannot merge as repos with duplicate names found: %s", strings.Join(duplicateRepos, ", "))
+		}
+
+		for _, r := range repos {
+			helper.FetchRemote(r, dryRun)
+			helper.MergeHistories(r, defaultBranch, dryRun)
+			helper.PrefixFiles(r, defaultBranch, dryRun)
+			helper.CommitChange(r, dryRun)
+			helper.RemoveRemote(r, dryRun)
+		}
+	},
+}
+
+func findDuplicateRepoNames(repos []*model.Repo) []string {
+	reposByName := map[string][]*model.Repo{}
+
+	for _, r := range repos {
+		if _, ok := reposByName[r.NameWithoutOrg()]; !ok {
+			reposByName[r.NameWithoutOrg()] = []*model.Repo{}
+		}
+
+		reposByName[r.NameWithoutOrg()] = append(reposByName[r.NameWithoutOrg()], r)
+	}
+
+	ret := []string{}
+	for name, repos := range reposByName {
+		if len(repos) > 1 {
+			ret = append(ret, name)
+		}
+	}
+
+	return ret
+}
+
+func init() {
+	rootCmd.AddCommand(runCmd)
+
+	runCmd.Flags().StringVarP(&defaultBranch, "branch", "b", "main", "TBD")
+
+	runCmd.Flags().BoolVar(&dryRun, "dry-run", false, "TBD")
+}

go.mod

@@ -1,3 +1,13 @@
 module github.com/oliverhohn/many2mono
 
 go 1.20
+
+require (
+	github.com/spf13/cobra v1.7.0
+	github.com/whilp/git-urls v1.0.0
+)
+
+require (
+	github.com/inconshreveable/mousetrap v1.1.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+)

go.sum

@@ -0,0 +1,12 @@
+github.com/cpuguy83/go-md2man/v2 v2.0.2/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
+github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
+github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
+github.com/spf13/cobra v1.7.0 h1:hyqWnYt1ZQShIddO5kBpj3vu05/++x6tJ6dg8EC572I=
+github.com/spf13/cobra v1.7.0/go.mod h1:uLxZILRyS/50WlhOIKD7W6V5bgeIt+4sICxh6uRMrb0=
+github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
+github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/whilp/git-urls v1.0.0 h1:95f6UMWN5FKW71ECsXRUd3FVYiXdrE7aX4NZKcPmIjU=
+github.com/whilp/git-urls v1.0.0/go.mod h1:J16SAmobsqc3Qcy98brfl5f5+e0clUvg1krgwk/qCfE=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

helper/operations.go

@@ -0,0 +1,69 @@
+package helper
+
+import (
+	"fmt"
+	"log"
+	"os/exec"
+
+	"github.com/oliverhohn/many2mono/model"
+)
+
+func FetchRemote(r *model.Repo, dryRun bool) {
+	cmd := exec.Command("git", "remote", "add", "-f", r.Name(), r.URL.String())
+
+	err := runCommand(cmd, dryRun)
+	if err != nil {
+		log.Fatalf("unable to fetch remote %s, due to: %v", r.URL.String(), err)
+	}
+}
+
+func RemoveRemote(r *model.Repo, dryRun bool) {
+	cmd := exec.Command("git", "remote", "remove", r.Name())
+
+	err := runCommand(cmd, dryRun)
+	if err != nil {
+		log.Fatalf("unable to remove remote %s, due to: %v", r.Name(), err)
+	}
+}
+
+func MergeHistories(r *model.Repo, branch string, dryRun bool) {
+	remote := fmt.Sprintf("%s/%s", r.Name(), branch)
+	cmd := exec.Command("git", "merge", "--allow-unrelated-histories", "--strategy=ours", "--no-commit", remote)
+
+	err := runCommand(cmd, dryRun)
+	if err != nil {
+		log.Fatalf("unable to merge histories from remote %s, due to: %v", remote, err)
+	}
+}
+
+func PrefixFiles(r *model.Repo, branch string, dryRun bool) {
+	remote := fmt.Sprintf("%s/%s", r.Name(), branch)
+	cmd := exec.Command("git", "read-tree", fmt.Sprintf("--prefix=%s", r.NameWithoutOrg()), "-u", remote)
+
+	err := runCommand(cmd, dryRun)
+	if err != nil {
+		log.Fatalf("unable to prefix files from remote %s, due to: %v", remote, err)
+	}
+}
+
+func CommitChange(r *model.Repo, dryRun bool) {
+	cmd := exec.Command("git", "commit", fmt.Sprintf("--message=\"Merged %s\"", r.Name()))
+
+	err := runCommand(cmd, dryRun)
+	if err != nil {
+		log.Fatalf("unable to commit merge from remote %s, due to: %v", r.Name(), err)
+	}
+}
+
+func runCommand(cmd *exec.Cmd, dryRun bool) error {
+	fmt.Printf("Running %s\n", cmd.String())
+
+	if !dryRun {
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("%v\ntrace:%s", err, out)
+		}
+	}
+
+	return nil
+}

main.go

@@ -1,7 +1,7 @@
 package main
 
-import "fmt"
+import "github.com/oliverhohn/many2mono/cmd"
 
 func main() {
-	fmt.Println("Hello, world!")
+	cmd.Execute()
 }

model/repo.go

@@ -0,0 +1,41 @@
+package model
+
+import (
+	"fmt"
+	"net/url"
+	"path/filepath"
+	"strings"
+
+	gitURLs "github.com/whilp/git-urls"
+)
+
+type Repo struct {
+	URL *url.URL
+}
+
+func NewRepo(path string) (*Repo, error) {
+	u, err := gitURLs.Parse(path)
+	if err != nil {
+		return nil, fmt.Errorf("unable to initialize repo from %s, due to: %w", path, err)
+	}
+
+	if u.Scheme != "ssh" {
+		return nil, fmt.Errorf("%s is an unsupported scheme for repo URLs, only ssh is supported", u.Scheme)
+	}
+
+	return &Repo{URL: u}, nil
+}
+
+func (r *Repo) Name() string {
+	ext := filepath.Ext(r.URL.Path)
+
+	name := strings.TrimSuffix(r.URL.Path, ext)
+
+	return strings.TrimSpace(name)
+}
+
+func (r *Repo) NameWithoutOrg() string {
+	nameComponents := strings.Split(r.Name(), "/")
+
+	return nameComponents[len(nameComponents)-1]
+}