Add a "Mark commit as base commit for rebase" command

This allows to do the equivalent of "git rebase --onto <target> <base>", by
first marking the <base> commit with the new command, and then selecting the
target branch and invoking the usual rebase command there.

10 files changed, 109 insertions, 10 deletions

diff --git a/pkg/gui/context/local_commits_context.go b/pkg/gui/context/local_commits_context.go
index 417a4f30a..f8f7848f2 100644
--- a/pkg/gui/context/local_commits_context.go
+++ b/pkg/gui/context/local_commits_context.go
@@ -49,6 +49,7 @@ func NewLocalCommitsContext(c *ContextCommon) *LocalCommitsContext {
 			c.State().GetRepoState().GetScreenMode() != types.SCREEN_NORMAL,
 			c.Modes().CherryPicking.SelectedShaSet(),
 			c.Modes().Diffing.Ref,
+			c.Modes().MarkedBaseCommit.GetSha(),
 			c.UserConfig.Gui.TimeFormat,
 			c.UserConfig.Gui.ShortTimeFormat,
 			time.Now(),
diff --git a/pkg/gui/context/sub_commits_context.go b/pkg/gui/context/sub_commits_context.go
index ba2f5e3f6..2643d294b 100644
--- a/pkg/gui/context/sub_commits_context.go
+++ b/pkg/gui/context/sub_commits_context.go
@@ -65,6 +65,7 @@ func NewSubCommitsContext(
 			c.State().GetRepoState().GetScreenMode() != types.SCREEN_NORMAL,
 			c.Modes().CherryPicking.SelectedShaSet(),
 			c.Modes().Diffing.Ref,
+			"",
 			c.UserConfig.Gui.TimeFormat,
 			c.UserConfig.Gui.ShortTimeFormat,
 			time.Now(),
diff --git a/pkg/gui/controllers/helpers/merge_and_rebase_helper.go b/pkg/gui/controllers/helpers/merge_and_rebase_helper.go
index e9140e102..03c3abb4b 100644
--- a/pkg/gui/controllers/helpers/merge_and_rebase_helper.go
+++ b/pkg/gui/controllers/helpers/merge_and_rebase_helper.go
@@ -224,8 +224,18 @@ func (self *MergeAndRebaseHelper) RebaseOntoRef(ref string) error {
 			Key:   's',
 			OnPress: func() error {
 				self.c.LogAction(self.c.Tr.Actions.RebaseBranch)
-				err := self.c.Git().Rebase.RebaseBranch(ref)
-				return self.CheckMergeOrRebase(err)
+				baseCommit := self.c.Modes().MarkedBaseCommit.GetSha()
+				var err error
+				if baseCommit != "" {
+					err = self.c.Git().Rebase.RebaseBranchFromBaseCommit(ref, baseCommit)
+				} else {
+					err = self.c.Git().Rebase.RebaseBranch(ref)
+				}
+				err = self.CheckMergeOrRebase(err)
+				if err == nil {
+					self.c.Modes().MarkedBaseCommit.Reset()
+				}
+				return err
 			},
 		},
 		{
@@ -234,17 +244,26 @@ func (self *MergeAndRebaseHelper) RebaseOntoRef(ref string) error {
 			Tooltip: self.c.Tr.InteractiveRebaseTooltip,
 			OnPress: func() error {
 				self.c.LogAction(self.c.Tr.Actions.RebaseBranch)
-				err := self.c.Git().Rebase.EditRebase(ref)
+				baseCommit := self.c.Modes().MarkedBaseCommit.GetSha()
+				var err error
+				if baseCommit != "" {
+					err = self.c.Git().Rebase.EditRebaseFromBaseCommit(ref, baseCommit)
+				} else {
+					err = self.c.Git().Rebase.EditRebase(ref)
+				}
 				if err = self.CheckMergeOrRebase(err); err != nil {
 					return err
 				}
+				self.c.Modes().MarkedBaseCommit.Reset()
 				return self.c.PushContext(self.c.Contexts().LocalCommits)
 			},
 		},
 	}
 
 	title := utils.ResolvePlaceholderString(
-		self.c.Tr.RebasingTitle,
+		lo.Ternary(self.c.Modes().MarkedBaseCommit.GetSha() != "",
+			self.c.Tr.RebasingFromBaseCommitTitle,
+			self.c.Tr.RebasingTitle),
 		map[string]string{
 			"checkedOutBranch": checkedOutBranch,
 			"ref":              ref,
@@ -283,3 +302,8 @@ func (self *MergeAndRebaseHelper) MergeRefIntoCheckedOutBranch(refName string) e
 		},
 	})
 }
+
+func (self *MergeAndRebaseHelper) ResetMarkedBaseCommit() error {
+	self.c.Modes().MarkedBaseCommit.Reset()
+	return self.c.PostRefreshUpdate(self.c.Contexts().LocalCommits)
+}
diff --git a/pkg/gui/controllers/helpers/mode_helper.go b/pkg/gui/controllers/helpers/mode_helper.go
index f5f3c738c..b3d9549a4 100644
--- a/pkg/gui/controllers/helpers/mode_helper.go
+++ b/pkg/gui/controllers/helpers/mode_helper.go
@@ -83,6 +83,16 @@ func (self *ModeHelper) Statuses() []ModeStatus {
 			Reset: self.ExitFilterMode,
 		},
 		{
+			IsActive: self.c.Modes().MarkedBaseCommit.Active,
+			Description: func() string {
+				return self.withResetButton(
+					self.c.Tr.MarkedBaseCommitStatus,
+					style.FgCyan,
+				)
+			},
+			Reset: self.mergeAndRebaseHelper.ResetMarkedBaseCommit,
+		},
+		{
 			IsActive: self.c.Modes().CherryPicking.Active,
 			Description: func() string {
 				copiedCount := len(self.c.Modes().CherryPicking.CherryPickedCommits)
diff --git a/pkg/gui/controllers/local_commits_controller.go b/pkg/gui/controllers/local_commits_controller.go
index a8df8811c..49f664a29 100644
--- a/pkg/gui/controllers/local_commits_controller.go
+++ b/pkg/gui/controllers/local_commits_controller.go
@@ -103,6 +103,12 @@ func (self *LocalCommitsController) GetKeybindings(opts types.KeybindingsOpts) [
 			Handler:     self.paste,
 			Description: self.c.Tr.PasteCommits,
 		},
+		{
+			Key:         opts.GetKey(opts.Config.Commits.MarkCommitAsBaseForRebase),
+			Handler:     self.checkSelected(self.markAsBaseCommit),
+			Description: self.c.Tr.MarkAsBaseCommit,
+			Tooltip:     self.c.Tr.MarkAsBaseCommitTooltip,
+		},
 		// overriding these navigation keybindings because we might need to load
 		// more commits on demand
 		{
@@ -840,6 +846,16 @@ func (self *LocalCommitsController) paste() error {
 	return self.c.Helpers().CherryPick.Paste()
 }
 
+func (self *LocalCommitsController) markAsBaseCommit(commit *models.Commit) error {
+	if commit.Sha == self.c.Modes().MarkedBaseCommit.GetSha() {
+		// Reset when invoking it again on the marked commit
+		self.c.Modes().MarkedBaseCommit.SetSha("")
+	} else {
+		self.c.Modes().MarkedBaseCommit.SetSha(commit.Sha)
+	}
+	return self.c.PostRefreshUpdate(self.c.Contexts().LocalCommits)
+}
+
 func (self *LocalCommitsController) isHeadCommit() bool {
 	return models.IsHeadCommit(self.c.Model().Commits, self.context().GetSelectedLineIdx())
 }
diff --git a/pkg/gui/gui.go b/pkg/gui/gui.go
index 8db98238c..4da5d5e96 100644
--- a/pkg/gui/gui.go
+++ b/pkg/gui/gui.go
@@ -24,6 +24,7 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/cherrypicking"
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/diffing"
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/filtering"
+	"github.com/jesseduffield/lazygit/pkg/gui/modes/marked_base_commit"
 	"github.com/jesseduffield/lazygit/pkg/gui/popup"
 	"github.com/jesseduffield/lazygit/pkg/gui/presentation"
 	"github.com/jesseduffield/lazygit/pkg/gui/presentation/authors"
@@ -362,9 +363,10 @@ func (gui *Gui) resetState(startArgs appTypes.StartArgs) types.Context {
 			Authors:               map[string]*models.Author{},
 		},
 		Modes: &types.Modes{
-			Filtering:     filtering.New(startArgs.FilterPath),
-			CherryPicking: cherrypicking.New(),
-			Diffing:       diffing.New(),
+			Filtering:        filtering.New(startArgs.FilterPath),
+			CherryPicking:    cherrypicking.New(),
+			Diffing:          diffing.New(),
+			MarkedBaseCommit: marked_base_commit.New(),
 		},
 		ScreenMode: initialScreenMode,
 		// TODO: only use contexts from context manager
diff --git a/pkg/gui/modes/marked_base_commit/marked_base_commit.go b/pkg/gui/modes/marked_base_commit/marked_base_commit.go
new file mode 100644
index 000000000..516dd0f2f
--- /dev/null
+++ b/pkg/gui/modes/marked_base_commit/marked_base_commit.go
@@ -0,0 +1,25 @@
+package marked_base_commit
+
+type MarkedBaseCommit struct {
+	sha string // the sha of the commit used as a rebase base commit; empty string when unset
+}
+
+func New() MarkedBaseCommit {
+	return MarkedBaseCommit{}
+}
+
+func (m *MarkedBaseCommit) Active() bool {
+	return m.sha != ""
+}
+
+func (m *MarkedBaseCommit) Reset() {
+	m.sha = ""
+}
+
+func (m *MarkedBaseCommit) SetSha(sha string) {
+	m.sha = sha
+}
+
+func (m *MarkedBaseCommit) GetSha() string {
+	return m.sha
+}
diff --git a/pkg/gui/presentation/commits.go b/pkg/gui/presentation/commits.go
index c00564e9d..f5915a7ee 100644
--- a/pkg/gui/presentation/commits.go
+++ b/pkg/gui/presentation/commits.go
@@ -45,6 +45,7 @@ func GetCommitListDisplayStrings(
 	fullDescription bool,
 	cherryPickedCommitShaSet *set.Set[string],
 	diffName string,
+	markedBaseCommit string,
 	timeFormat string,
 	shortTimeFormat string,
 	now time.Time,
@@ -128,6 +129,7 @@ func GetCommitListDisplayStrings(
 
 	lines := make([][]string, 0, len(filteredCommits))
 	var bisectStatus BisectStatus
+	willBeRebased := markedBaseCommit == ""
 	for i, commit := range filteredCommits {
 		unfilteredIdx := i + startIdx
 		bisectStatus = getBisectStatus(unfilteredIdx, commit.Sha, bisectInfo, bisectBounds)
@@ -136,11 +138,17 @@ func GetCommitListDisplayStrings(
 			isYouAreHereCommit = true
 			showYouAreHereLabel = false
 		}
+		isMarkedBaseCommit := commit.Sha != "" && commit.Sha == markedBaseCommit
+		if isMarkedBaseCommit {
+			willBeRebased = true
+		}
 		lines = append(lines, displayCommit(
 			common,
 			commit,
 			branchHeadsToVisualize,
 			cherryPickedCommitShaSet,
+			isMarkedBaseCommit,
+			willBeRebased,
 			diffName,
 			timeFormat,
 			shortTimeFormat,
@@ -290,6 +298,8 @@ func displayCommit(
 	commit *models.Commit,
 	branchHeadsToVisualize *set.Set[string],
 	cherryPickedCommitShaSet *set.Set[string],
+	isMarkedBaseCommit bool,
+	willBeRebased bool,
 	diffName string,
 	timeFormat string,
 	shortTimeFormat string,
@@ -335,6 +345,12 @@ func displayCommit(
 		color := lo.Ternary(commit.Action == models.ActionConflict, style.FgRed, style.FgYellow)
 		youAreHere := color.Sprintf("<-- %s ---", common.Tr.YouAreHere)
 		name = fmt.Sprintf("%s %s", youAreHere, name)
+	} else if isMarkedBaseCommit {
+		rebaseFromHere := style.FgYellow.Sprint(common.Tr.MarkedCommitMarker)
+		name = fmt.Sprintf("%s %s", rebaseFromHere, name)
+	} else if !willBeRebased {
+		willBeRebased := style.FgYellow.Sprint("✓")
+		name = fmt.Sprintf("%s %s", willBeRebased, name)
 	}
 
 	authorFunc := authors.ShortAuthor
diff --git a/pkg/gui/presentation/commits_test.go b/pkg/gui/presentation/commits_test.go
index 4bf4c09af..65122961e 100644
--- a/pkg/gui/presentation/commits_test.go
+++ b/pkg/gui/presentation/commits_test.go
@@ -33,6 +33,7 @@ func TestGetCommitListDisplayStrings(t *testing.T) {
 		hasUpdateRefConfig       bool
 		fullDescription          bool
 		cherryPickedCommitShaSet *set.Set[string]
+		markedBaseCommit         string
 		diffName                 string
 		timeFormat               string
 		shortTimeFormat          string
@@ -408,6 +409,7 @@ func TestGetCommitListDisplayStrings(t *testing.T) {
 					s.fullDescription,
 					s.cherryPickedCommitShaSet,
 					s.diffName,
+					s.markedBaseCommit,
 					s.timeFormat,
 					s.shortTimeFormat,
 					s.now,
diff --git a/pkg/gui/types/modes.go b/pkg/gui/types/modes.go
index ba135de63..a11ed0081 100644
--- a/pkg/gui/types/modes.go
+++ b/pkg/gui/types/modes.go
@@ -4,10 +4,12 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/cherrypicking"
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/diffing"
 	"github.com/jesseduffield/lazygit/pkg/gui/modes/filtering"
+	"github.com/jesseduffield/lazygit/pkg/gui/modes/marked_base_commit"
 )
 
 type Modes struct {
-	Filtering     filtering.Filtering
-	CherryPicking *cherrypicking.CherryPicking
-	Diffing       diffing.Diffing
+	Filtering        filtering.Filtering
+	CherryPicking    *cherrypicking.CherryPicking
+	Diffing          diffing.Diffing
+	MarkedBaseCommit marked_base_commit.MarkedBaseCommit
 }