Add ahead/behind detection, clean up tests

new/status.go

@@ -1,6 +1,9 @@
 package new
 
 import (
+	"sort"
+	"strings"
+
 	"github.com/go-git/go-git/v5"
 	"github.com/go-git/go-git/v5/plumbing"
 	"github.com/pkg/errors"
@@ -9,21 +12,14 @@ import (
 type RepoStatus struct {
 	HasUntrackedFiles     bool
 	HasUncommittedChanges bool
-	Branches              map[string]*BranchStatus
+	Branches              []*BranchStatus
 }
 
 type BranchStatus struct {
 	Name      string
-	Upstream  *Upstream
+	Upstream  string
 	NeedsPull bool
 	NeedsPush bool
-	Ahead     int
-	Behind    int
-}
-
-type Upstream struct {
-	Remote string
-	Branch string
 }
 
 func (r *Repo) LoadStatus() error {
@@ -37,10 +33,10 @@ func (r *Repo) LoadStatus() error {
 		return errors.Wrap(err, "Failed getting worktree status")
 	}
 
-	r.Status.HasUncommittedChanges = !status.IsClean()
+	r.Status.HasUncommittedChanges = hasUncommitted(status)
 	r.Status.HasUntrackedFiles = hasUntracked(status)
 
-	err = r.LoadBranchesStatus()
+	err = r.loadBranchesStatus()
 	if err != nil {
 		return err
 	}
@@ -51,15 +47,32 @@ func (r *Repo) LoadStatus() error {
 // hasUntracked returns true if there are any untracked files in the worktree
 func hasUntracked(status git.Status) bool {
 	for _, fs := range status {
-		if fs.Worktree == git.Untracked {
+		if fs.Worktree == git.Untracked || fs.Staging == git.Untracked {
 			return true
 		}
 	}
-	return false
 
+	return false
 }
 
-func (r *Repo) LoadBranchesStatus() error {
+// hasUncommitted returns true if there are any uncommitted (but tracked) files in the worktree
+func hasUncommitted(status git.Status) bool {
+	// If repo is clean it means every file in worktree and staging has 'Unmodified' state
+	if status.IsClean() {
+		return false
+	}
+
+	// If repo is not clean, check if any file has state different than 'Untracked' - it means they are tracked and have uncommitted modifications
+	for _, fs := range status {
+		if fs.Worktree != git.Untracked || fs.Staging != git.Untracked {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (r *Repo) loadBranchesStatus() error {
 	iter, err := r.repo.Branches()
 	if err != nil {
 		return errors.Wrap(err, "Failed getting branches iterator")
@@ -71,60 +84,132 @@ func (r *Repo) LoadBranchesStatus() error {
 			return err
 		}
 
-		r.Status.Branches[bs.Name] = bs
+		r.Status.Branches = append(r.Status.Branches, bs)
 		return nil
 	})
 	if err != nil {
 		return errors.Wrap(err, "Failed iterating over branches")
 	}
 
+	// Sort branches by name. It's useful to have them sorted for printing and testing.
+	sort.Slice(r.Status.Branches, func(i, j int) bool {
+		return strings.Compare(r.Status.Branches[i].Name, r.Status.Branches[j].Name) < 0
+	})
 	return nil
 }
 
 func (r *Repo) newBranchStatus(branch string) (*BranchStatus, error) {
+	bs := &BranchStatus{
+		Name: branch,
+	}
+
 	upstream, err := r.upstream(branch)
 	if err != nil {
 		return nil, err
 	}
 
-	return &BranchStatus{
-		Name:     branch,
-		Upstream: upstream,
-	}, nil
+	if upstream == "" {
+		return bs, nil
+	}
+
+	needsPull, needsPush, err := r.needsPullOrPush(branch, upstream)
+	if err != nil {
+		return nil, err
+	}
+
+	bs.Upstream = upstream
+	bs.NeedsPush = needsPush
+	bs.NeedsPull = needsPull
+
+	return bs, nil
 }
 
 // upstream finds if a given branch tracks an upstream.
-// Returns found upstream or nil if branch doesn't track an upstream.
+// Returns found upstream branch name (eg, origin/master) or empty string if branch doesn't track an upstream.
 //
 // Information about upstream is taken from .git/config file.
 // If a branch has an upstream, there's a [branch] section in the file with two fields:
 // "remote" - name of the remote containing upstreamn branch (or "." if upstream is a local branch)
 // "merge" - full ref name of the upstream branch (eg, ref/heads/master)
-func (r *Repo) upstream(branch string) (*Upstream, error) {
+func (r *Repo) upstream(branch string) (string, error) {
 	cfg, err := r.repo.Config()
 	if err != nil {
-		return nil, errors.Wrap(err, "Failed getting repo config")
+		return "", errors.Wrap(err, "Failed getting repo config")
 	}
 
-	// Find our branch in "branch" config sections
+	// Check if our branch exists in "branch" config sections. If not, it doesn't have an upstream configured.
 	bcfg := cfg.Branches[branch]
 	if bcfg == nil {
-		return nil, nil
+		return "", nil
 	}
 
 	remote := bcfg.Remote
 	if remote == "" {
-		return nil, nil
+		return "", nil
 	}
 
-	// TODO: check if this should be short or full ref name
 	merge := bcfg.Merge.Short()
 	if merge == "" {
-		return nil, nil
+		return "", nil
+	}
+	return remote + "/" + merge, nil
+}
+
+func (r *Repo) needsPullOrPush(localBranch string, upstreamBranch string) (needsPull bool, needsPush bool, err error) {
+	localHash, err := r.repo.ResolveRevision(plumbing.Revision(localBranch))
+	if err != nil {
+		return false, false, errors.Wrapf(err, "Failed resolving revision %s", localBranch)
 	}
 
-	return &Upstream{
-		Remote: remote,
-		Branch: merge,
-	}, nil
+	upstreamHash, err := r.repo.ResolveRevision(plumbing.Revision(upstreamBranch))
+	if err != nil {
+		return false, false, errors.Wrapf(err, "Failed resolving revision %s", upstreamBranch)
+	}
+
+	localCommit, err := r.repo.CommitObject(*localHash)
+	if err != nil {
+		return false, false, errors.Wrapf(err, "Failed finding a commit for hash %s", localHash.String())
+	}
+
+	upstreamCommit, err := r.repo.CommitObject(*upstreamHash)
+	if err != nil {
+		return false, false, errors.Wrapf(err, "Failed finding a commit for hash %s", upstreamHash.String())
+	}
+
+	// If local branch hash is the same as upstream, it means there is no difference between local and upstream
+	if *localHash == *upstreamHash {
+		return false, false, nil
+	}
+
+	commons, err := localCommit.MergeBase(upstreamCommit)
+	if err != nil {
+		return false, false, errors.Wrapf(err, "Failed finding common ancestors for branches %s & %s", localBranch, upstreamBranch)
+	}
+
+	if len(commons) == 0 {
+		// TODO: No common ancestors. This should be an error
+		return false, false, nil
+	}
+
+	if len(commons) > 1 {
+		// TODO: multiple best ancestors. How to handle this?
+		return false, false, nil
+	}
+
+	mergeBase := commons[0]
+
+	// If merge base is the same as upstream branch, local branch is ahead and push is needed
+	// If merge base is the same as local branch, local branch is behind and pull is needed
+	// If merge base is something else, branches have diverged and merge is needed (both pull and push)
+	// ref: https://stackoverflow.com/a/17723781/1085632
+
+	if mergeBase.Hash == *upstreamHash {
+		return false, true, nil
+	}
+
+	if mergeBase.Hash == *localHash {
+		return true, false, nil
+	}
+
+	return true, true, nil
 }