load reflog commits in two stages to speed up startup time

pkg/commands/git.go

@@ -1116,13 +1116,24 @@ func (c *GitCommand) FetchRemote(remoteName string) error {
 	return c.OSCommand.RunCommand("git fetch %s", remoteName)
 }
 
-// GetNewReflogCommits only returns the new reflog commits since the given lastReflogCommit
+type GetReflogCommitsOptions struct {
+	Limit   int
+	Recycle bool
+}
+
+// GetReflogCommits only returns the new reflog commits since the given lastReflogCommit
 // if none is passed (i.e. it's value is nil) then we get all the reflog commits
-func (c *GitCommand) GetNewReflogCommits(lastReflogCommit *Commit) ([]*Commit, bool, error) {
+func (c *GitCommand) GetReflogCommits(lastReflogCommit *Commit, options GetReflogCommitsOptions) ([]*Commit, bool, error) {
 	commits := make([]*Commit, 0)
 	re := regexp.MustCompile(`(\w+).*HEAD@\{([^\}]+)\}: (.*)`)
-	cmd := c.OSCommand.ExecutableFromString("git reflog --abbrev=20 --date=unix")
+
-	foundLastReflogCommit := false
+	limitArg := ""
+	if options.Limit > 0 {
+		limitArg = fmt.Sprintf("-%d", options.Limit)
+	}
+
+	cmd := c.OSCommand.ExecutableFromString(fmt.Sprintf("git reflog --abbrev=20 --date=unix %s", limitArg))
+	onlyObtainedNewReflogCommits := false
 	err := RunLineOutputCmd(cmd, func(line string) (bool, error) {
 		match := re.FindStringSubmatch(line)
 		if len(match) <= 1 {
@@ -1138,8 +1149,8 @@ func (c *GitCommand) GetNewReflogCommits(lastReflogCommit *Commit) ([]*Commit, b
 			Status:        "reflog",
 		}
 
-		if lastReflogCommit != nil && commit.Sha == lastReflogCommit.Sha && commit.UnixTimestamp == lastReflogCommit.UnixTimestamp {
+		if options.Recycle && lastReflogCommit != nil && commit.Sha == lastReflogCommit.Sha && commit.UnixTimestamp == lastReflogCommit.UnixTimestamp {
-			foundLastReflogCommit = true
+			onlyObtainedNewReflogCommits = true
 			// after this point we already have these reflogs loaded so we'll simply return the new ones
 			return true, nil
 		}
@@ -1151,7 +1162,7 @@ func (c *GitCommand) GetNewReflogCommits(lastReflogCommit *Commit) ([]*Commit, b
 		return nil, false, err
 	}
 
-	return commits, foundLastReflogCommit, nil
+	return commits, onlyObtainedNewReflogCommits, nil
 }
 
 func (c *GitCommand) ConfiguredPager() string {

pkg/gui/branches_panel.go

@@ -64,6 +64,8 @@ func (gui *Gui) refreshBranches() {
 	if gui.getBranchesView().Context == "local-branches" {
 		gui.renderLocalBranchesWithSelection()
 	}
+
+	gui.refreshStatus()
 }
 
 func (gui *Gui) renderLocalBranchesWithSelection() error {

pkg/gui/commits_panel.go

@@ -71,21 +71,40 @@ func (gui *Gui) handleCommitSelect(g *gocui.Gui, v *gocui.View) error {
 	return nil
 }
 
+// during startup, the bottleneck is fetching the reflog entries. We need these
+// on startup to sort the branches by recency. So we have two phases: INITIAL, and COMPLETE.
+// In the initial phase we get a small set of reflog entries so that we can ensure
+// the first couple of branches are correctly positioned. Then we asynchronously
+// refresh the reflog again, without a limit, and refresh the branches again when that's done.
+// When we're complete, we can begin recycling reflog entries because we know we've got
+// everything down to the oldest entry.
+func (gui *Gui) refreshReflogCommitsConsideringStartup() {
+	switch gui.State.StartupStage {
+	case INITIAL:
+		gui.refreshReflogCommits(refreshReflogOptions{Limit: 100, Recycle: false})
+
+		go func() {
+			gui.refreshReflogCommits(refreshReflogOptions{Recycle: false})
+			gui.refreshBranches()
+			gui.State.StartupStage = COMPLETE
+		}()
+
+	case COMPLETE:
+		gui.refreshReflogCommits(refreshReflogOptions{Recycle: true})
+	}
+}
+
 // whenever we change commits, we should update branches because the upstream/downstream
 // counts can change. Whenever we change branches we should probably also change commits
-// e.g. in the case of switching branches. We also need the status to be refreshed whenever
+// e.g. in the case of switching branches.
-// the working tree status changes or the branch upstream/downstream value changes.
-// Given how fast the refreshStatus method is, we should really just call it every time
-// we refresh, but I'm not sure how to do that asynchronously that prevents a race condition
-// other than a mutex.
 func (gui *Gui) refreshCommits() error {
 	wg := sync.WaitGroup{}
 	wg.Add(2)
 
 	go func() {
-		gui.refreshReflogCommits()
+		gui.refreshReflogCommitsConsideringStartup()
+
 		gui.refreshBranches()
-		gui.refreshStatus()
 		wg.Done()
 	}()
 

pkg/gui/gui.go

@@ -178,6 +178,12 @@ type searchingState struct {
 	searchString string
 }
 
+// startup stages so we don't need to load everything at once
+const (
+	INITIAL = iota
+	COMPLETE
+)
+
 type guiState struct {
 	Files                 []*commands.File
 	Branches              []*commands.Branch
@@ -208,6 +214,7 @@ type guiState struct {
 	PrevMainWidth         int
 	PrevMainHeight        int
 	OldInformation        string
+	StartupStage          int // one of INITIAL and COMPLETE. Allows us to not load everything at once
 }
 
 // for now the split view will always be on

pkg/gui/reflog_panel.go

@@ -46,18 +46,23 @@ func (gui *Gui) handleReflogCommitSelect(g *gocui.Gui, v *gocui.View) error {
 	return nil
 }
 
-func (gui *Gui) refreshReflogCommits() error {
+type refreshReflogOptions struct {
+	Limit   int
+	Recycle bool
+}
+
+func (gui *Gui) refreshReflogCommits(options refreshReflogOptions) error {
 	var lastReflogCommit *commands.Commit
 	if len(gui.State.ReflogCommits) > 0 {
 		lastReflogCommit = gui.State.ReflogCommits[0]
 	}
 
-	commits, foundLastReflogCommit, err := gui.GitCommand.GetNewReflogCommits(lastReflogCommit)
+	commits, onlyObtainedNewReflogCommits, err := gui.GitCommand.GetReflogCommits(lastReflogCommit, commands.GetReflogCommitsOptions(options))
 	if err != nil {
 		return gui.createErrorPanel(gui.g, err.Error())
 	}
 
-	if foundLastReflogCommit {
+	if onlyObtainedNewReflogCommits {
 		gui.State.ReflogCommits = append(commits, gui.State.ReflogCommits...)
 	} else {
 		// if we haven't found it we're probably in a new repo so we don't want to