Fix MR Selection, Go Code Refactor (#358)

refactor: Refactors the Go codebase into a more modular and idiomatic approach
fix: require selection of specific MR when there are multiple targets for a given source branch
feat: Allows for the passing of Gitlab's filter options when choosing an MR, improves MR selection
feat: API to choose an MR from a list based on the provided username's involvement as an assignee/reviewer/author

This is a #MINOR release

cmd/app/git/git.go

@@ -0,0 +1,131 @@
+package git
+
+import (
+	"fmt"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+type GitManager interface {
+	RefreshProjectInfo(remote string) error
+	GetProjectUrlFromNativeGitCmd(remote string) (url string, err error)
+	GetCurrentBranchNameFromNativeGitCmd() (string, error)
+	GetLatestCommitOnRemote(remote string, branchName string) (string, error)
+}
+
+type GitData struct {
+	RemoteUrl   string
+	Namespace   string
+	ProjectName string
+	BranchName  string
+}
+
+type Git struct{}
+
+/*
+projectPath returns the Gitlab project full path, which isn't necessarily the same as its name.
+See https://docs.gitlab.com/ee/api/rest/index.html#namespaced-path-encoding for more information.
+*/
+func (g GitData) ProjectPath() string {
+	return g.Namespace + "/" + g.ProjectName
+}
+
+/*
+Extracts information about the current repository and returns
+it to the client for initialization. The current directory must be a valid
+Gitlab project and the branch must be a feature branch
+*/
+func NewGitData(remote string, g GitManager) (GitData, error) {
+	err := g.RefreshProjectInfo(remote)
+	if err != nil {
+		return GitData{}, fmt.Errorf("Could not get latest information from remote: %v", err)
+	}
+
+	url, err := g.GetProjectUrlFromNativeGitCmd(remote)
+	if err != nil {
+		return GitData{}, fmt.Errorf("Could not get project Url: %v", err)
+	}
+
+	/*
+	   This should match following formats:
+	       namespace: namespace, projectName: dummy-test-repo:
+	           https://gitlab.com/namespace/dummy-test-repo.git
+	           git@gitlab.com:namespace/dummy-test-repo.git
+	           ssh://git@gitlab.com/namespace/dummy-test-repo.git
+
+	       namespace: namespace/subnamespace, projectName: dummy-test-repo:
+	           ssh://git@gitlab.com/namespace/subnamespace/dummy-test-repo
+	           https://git@gitlab.com/namespace/subnamespace/dummy-test-repo.git
+	           git@git@gitlab.com:namespace/subnamespace/dummy-test-repo.git
+	*/
+	re := regexp.MustCompile(`(?:^https?:\/\/|^ssh:\/\/|^git@)(?:[^\/:]+)(?::\d+)?[\/:](.*)\/([^\/]+?)(?:\.git)?$`)
+	matches := re.FindStringSubmatch(url)
+	if len(matches) != 3 {
+		return GitData{}, fmt.Errorf("Invalid Git URL format: %s", url)
+	}
+
+	namespace := matches[1]
+	projectName := matches[2]
+
+	branchName, err := g.GetCurrentBranchNameFromNativeGitCmd()
+	if err != nil {
+		return GitData{}, fmt.Errorf("Failed to get current branch: %v", err)
+	}
+
+	return GitData{
+			RemoteUrl:   url,
+			Namespace:   namespace,
+			ProjectName: projectName,
+			BranchName:  branchName,
+		},
+		nil
+}
+
+/* Gets the current branch name */
+func (g Git) GetCurrentBranchNameFromNativeGitCmd() (res string, e error) {
+	gitCmd := exec.Command("git", "rev-parse", "--abbrev-ref", "HEAD")
+
+	output, err := gitCmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("Error running git rev-parse: %w", err)
+	}
+
+	branchName := strings.TrimSpace(string(output))
+
+	return branchName, nil
+}
+
+/* Gets the project SSH or HTTPS url */
+func (g Git) GetProjectUrlFromNativeGitCmd(remote string) (string, error) {
+	cmd := exec.Command("git", "remote", "get-url", remote)
+	url, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("Could not get remote")
+	}
+
+	return strings.TrimSpace(string(url)), nil
+}
+
+/* Pulls down latest commit information from Gitlab */
+func (g Git) RefreshProjectInfo(remote string) error {
+	cmd := exec.Command("git", "fetch", remote)
+	_, err := cmd.Output()
+	if err != nil {
+		return fmt.Errorf("Failed to run `git fetch %s`: %v", remote, err)
+	}
+
+	return nil
+}
+
+func (g Git) GetLatestCommitOnRemote(remote string, branchName string) (string, error) {
+	cmd := exec.Command("git", "log", "-1", "--format=%H", fmt.Sprintf("%s/%s", remote, branchName))
+
+	out, err := cmd.Output()
+	if err != nil {
+		return "", fmt.Errorf("Failed to run `git log -1 --format=%%H " + fmt.Sprintf("%s/%s", remote, branchName))
+	}
+
+	commit := strings.TrimSpace(string(out))
+	return commit, nil
+}