1 files changed, 163 insertions, 0 deletions
diff --git a/core/command/fetch.go b/core/command/fetch.go
new file mode 100644
index 0000000..cc827bf
--- /dev/null
+++ b/core/command/fetch.go
@@ -0,0 +1,163 @@
+package command
+
+import (
+	"os"
+	"strings"
+
+	gerr "github.com/isacikgoz/gitbatch/core/errors"
+	"github.com/isacikgoz/gitbatch/core/git"
+	log "github.com/sirupsen/logrus"
+	gogit "gopkg.in/src-d/go-git.v4"
+	"gopkg.in/src-d/go-git.v4/config"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport"
+	"gopkg.in/src-d/go-git.v4/plumbing/transport/http"
+)
+
+var (
+	fetchCmdMode  string
+	fetchTryCount int
+
+	fetchCommand       = "fetch"
+	fetchCmdModeLegacy = "git"
+	fetchCmdModeNative = "go-git"
+	fetchMaxTry        = 1
+)
+
+// FetchOptions defines the rules for fetch operation
+type FetchOptions struct {
+	// Name of the remote to fetch from. Defaults to origin.
+	RemoteName string
+	// Credentials holds the user and pswd information
+	Credentials git.Credentials
+	// Before fetching, remove any remote-tracking references that no longer
+	// exist on the remote.
+	Prune bool
+	// Show what would be done, without making any changes.
+	DryRun bool
+	// Process logs the output to stdout
+	Progress bool
+	// Force allows the fetch to update a local branch even when the remote
+	// branch does not descend from it.
+	Force bool
+	// There should be more room for authentication, tags and progress
+}
+
+// Fetch branches refs from one or more other repositories, along with the
+// objects necessary to complete their histories
+func Fetch(r *git.Repository, options FetchOptions) (err error) {
+	// here we configure fetch operation
+	// default mode is go-git (this may be configured)
+	fetchCmdMode = fetchCmdModeNative
+	fetchTryCount = 0
+	// prune and dry run is not supported from go-git yet, rely on old friend
+	if options.Prune || options.DryRun {
+		fetchCmdMode = fetchCmdModeLegacy
+	}
+	switch fetchCmdMode {
+	case fetchCmdModeLegacy:
+		err = fetchWithGit(r, options)
+		return err
+	case fetchCmdModeNative:
+		// this should be the refspec as default, let's give it a try
+		// TODO: Fix for quick mode, maybe better read config file
+		var refspec string
+		if r.State.Branch == nil {
+			refspec = "+refs/heads/*:refs/remotes/origin/*"
+		} else {
+			refspec = "+" + "refs/heads/" + r.State.Branch.Name + ":" + "/refs/remotes/" + r.State.Remote.Branch.Name
+		}
+		err = fetchWithGoGit(r, options, refspec)
+		return err
+	}
+	return nil
+}
+
+// fetchWithGit is simply a bare git fetch <remote> command which is flexible
+// for complex operations, but on the other hand, it ties the app to another
+// tool. To avoid that, using native implementation is preferred.
+func fetchWithGit(r *git.Repository, options FetchOptions) (err error) {
+	args := make([]string, 0)
+	args = append(args, fetchCommand)
+	// parse options to command line arguments
+	if len(options.RemoteName) > 0 {
+		args = append(args, options.RemoteName)
+	}
+	if options.Prune {
+		args = append(args, "-p")
+	}
+	if options.Force {
+		args = append(args, "-f")
+	}
+	if options.DryRun {
+		args = append(args, "--dry-run")
+	}
+	if out, err := GenericGitCommandWithOutput(r.AbsPath, args); err != nil {
+		return gerr.ParseGitError(out, err)
+	}
+	r.SetWorkStatus(git.Success)
+	// till this step everything should be ok
+	return r.Refresh()
+}
+
+// fetchWithGoGit is the primary fetch method and refspec is the main feature.
+// RefSpec is a mapping from local branches to remote references The format of
+// the refspec is an optional +, followed by <src>:<dst>, where <src> is the
+// pattern for references on the remote side and <dst> is where those references
+// will be written locally. The + tells Git to update the reference even if it
+// isn’t a fast-forward.
+func fetchWithGoGit(r *git.Repository, options FetchOptions, refspec string) (err error) {
+	opt := &gogit.FetchOptions{
+		RemoteName: options.RemoteName,
+		RefSpecs:   []config.RefSpec{config.RefSpec(refspec)},
+		Force:      options.Force,
+	}
+	// if any credential is given, let's add it to the git.FetchOptions
+	if len(options.Credentials.User) > 0 {
+		protocol, err := git.AuthProtocol(r.State.Remote)
+		if err != nil {
+			return err
+		}
+		if protocol == git.AuthProtocolHTTP || protocol == git.AuthProtocolHTTPS {
+			opt.Auth = &http.BasicAuth{
+				Username: options.Credentials.User,
+				Password: options.Credentials.Password,
+			}
+		} else {
+			return gerr.ErrInvalidAuthMethod
+		}
+	}
+	if options.Progress {
+		opt.Progress = os.Stdout
+	}
+
+	if err := r.Repo.Fetch(opt); err != nil {
+		if err == gogit.NoErrAlreadyUpToDate {
+			// Already up-to-date
+			log.Warn(err.Error())
+			// TODO: submit a PR for this kind of error, this type of catch is lame
+		} else if strings.Contains(err.Error(), "couldn't find remote ref") {
+			// we dont have remote ref, so lets pull other things.. maybe it'd be useful
+			rp := r.State.Remote.RefSpecs[0]
+			if fetchTryCount < fetchMaxTry {
+				fetchTryCount++
+				fetchWithGoGit(r, options, rp)
+			} else {
+				return err
+			}
+			// TODO: submit a PR for this kind of error, this type of catch is lame
+		} else if strings.Contains(err.Error(), "SSH_AUTH_SOCK") {
+			// The env variable SSH_AUTH_SOCK is not defined, maybe git can handle this
+			return fetchWithGit(r, options)
+		} else if err == transport.ErrAuthenticationRequired {
+			log.Warn(err.Error())
+			return gerr.ErrAuthenticationRequired
+		} else {
+			log.Warn(err.Error())
+			return fetchWithGit(r, options)
+		}
+	}
+
+	r.SetWorkStatus(git.Success)
+	// till this step everything should be ok
+	return r.Refresh()
+}