Add command to find base commit for creating a fixup

pkg/gui/controllers/files_controller.go

@@ -64,6 +64,12 @@ func (self *FilesController) GetKeybindings(opts types.KeybindingsOpts) []*types
 			Handler:     self.c.Helpers().WorkingTree.HandleCommitEditorPress,
 			Description: self.c.Tr.CommitChangesWithEditor,
 		},
+		{
+			Key:         opts.GetKey(opts.Config.Files.FindBaseCommitForFixup),
+			Handler:     self.c.Helpers().FixupHelper.HandleFindBaseCommitForFixupPress,
+			Description: self.c.Tr.FindBaseCommitForFixup,
+			Tooltip:     self.c.Tr.FindBaseCommitForFixupTooltip,
+		},
 		{
 			Key:         opts.GetKey(opts.Config.Universal.Edit),
 			Handler:     self.checkSelectedFileNode(self.edit),

pkg/gui/controllers/helpers/fixup_helper.go

@@ -0,0 +1,178 @@
+package helpers
+
+import (
+	"regexp"
+	"strings"
+	"sync"
+
+	"github.com/jesseduffield/generics/set"
+	"github.com/jesseduffield/lazygit/pkg/commands/models"
+	"github.com/jesseduffield/lazygit/pkg/gui/types"
+	"github.com/jesseduffield/lazygit/pkg/utils"
+	"github.com/samber/lo"
+)
+
+type FixupHelper struct {
+	c *HelperCommon
+}
+
+func NewFixupHelper(
+	c *HelperCommon,
+) *FixupHelper {
+	return &FixupHelper{
+		c: c,
+	}
+}
+
+type deletedLineInfo struct {
+	filename     string
+	startLineIdx int
+	numLines     int
+}
+
+func (self *FixupHelper) HandleFindBaseCommitForFixupPress() error {
+	diff, hasStagedChanges, err := self.getDiff()
+	if err != nil {
+		return err
+	}
+	if diff == "" {
+		return self.c.ErrorMsg(self.c.Tr.NoChangedFiles)
+	}
+
+	deletedLineInfos := self.parseDiff(diff)
+	if len(deletedLineInfos) == 0 {
+		return self.c.ErrorMsg(self.c.Tr.NoDeletedLinesInDiff)
+	}
+
+	shas := self.blameDeletedLines(deletedLineInfos)
+
+	if len(shas) == 0 {
+		// This should never happen
+		return self.c.ErrorMsg(self.c.Tr.NoBaseCommitsFound)
+	}
+	if len(shas) > 1 {
+		subjects, err := self.c.Git().Commit.GetShasAndCommitMessagesFirstLine(shas)
+		if err != nil {
+			return err
+		}
+		message := lo.Ternary(hasStagedChanges,
+			self.c.Tr.MultipleBaseCommitsFoundStaged,
+			self.c.Tr.MultipleBaseCommitsFoundUnstaged)
+		return self.c.ErrorMsg(message + "\n\n" + subjects)
+	}
+
+	commit, index, ok := lo.FindIndexOf(self.c.Model().Commits, func(commit *models.Commit) bool {
+		return commit.Sha == shas[0]
+	})
+	if !ok {
+		commits := self.c.Model().Commits
+		if commits[len(commits)-1].Status == models.StatusMerged {
+			// If the commit is not found, it's most likely because it's already
+			// merged, and more than 300 commits away. Check if the last known
+			// commit is already merged; if so, show the "already merged" error.
+			return self.c.ErrorMsg(self.c.Tr.BaseCommitIsAlreadyOnMainBranch)
+		}
+		// If we get here, the current branch must have more then 300 commits. Unlikely...
+		return self.c.ErrorMsg(self.c.Tr.BaseCommitIsNotInCurrentView)
+	}
+	if commit.Status == models.StatusMerged {
+		return self.c.ErrorMsg(self.c.Tr.BaseCommitIsAlreadyOnMainBranch)
+	}
+
+	if !useIndex {
+		if err := self.c.Git().WorkingTree.StageAll(); err != nil {
+			return err
+		}
+		_ = self.c.Refresh(types.RefreshOptions{Mode: types.SYNC, Scope: []types.RefreshableView{types.FILES}})
+	}
+
+	self.c.Contexts().LocalCommits.SetSelectedLineIdx(index)
+	return self.c.PushContext(self.c.Contexts().LocalCommits)
+}
+
+func (self *FixupHelper) getDiff() (string, bool, error) {
+	args := []string{"-U0", "--ignore-submodules=all", "HEAD", "--"}
+
+	// Try staged changes first
+	hasStagedChanges := true
+	diff, err := self.c.Git().Diff.DiffIndexCmdObj(append([]string{"--cached"}, args...)...).RunWithOutput()
+
+	if err == nil && diff == "" {
+		hasStagedChanges = false
+		// If there are no staged changes, try unstaged changes
+		diff, err = self.c.Git().Diff.DiffIndexCmdObj(args...).RunWithOutput()
+	}
+
+	return diff, hasStagedChanges, err
+}
+
+func (self *FixupHelper) parseDiff(diff string) []*deletedLineInfo {
+	lines := strings.Split(strings.TrimSuffix(diff, "\n"), "\n")
+
+	deletedLineInfos := []*deletedLineInfo{}
+
+	hunkHeaderRegexp := regexp.MustCompile(`@@ -(\d+)(?:,\d+)? \+\d+(?:,\d+)? @@`)
+
+	var filename string
+	var currentLineInfo *deletedLineInfo
+	finishHunk := func() {
+		if currentLineInfo != nil && currentLineInfo.numLines > 0 {
+			deletedLineInfos = append(deletedLineInfos, currentLineInfo)
+		}
+	}
+	for _, line := range lines {
+		if strings.HasPrefix(line, "diff --git") {
+			finishHunk()
+			currentLineInfo = nil
+		} else if strings.HasPrefix(line, "--- ") {
+			// For some reason, the line ends with a tab character if the file
+			// name contains spaces
+			filename = strings.TrimRight(line[6:], "\t")
+		} else if strings.HasPrefix(line, "@@ ") {
+			finishHunk()
+			match := hunkHeaderRegexp.FindStringSubmatch(line)
+			startIdx := utils.MustConvertToInt(match[1])
+			currentLineInfo = &deletedLineInfo{filename, startIdx, 0}
+		} else if currentLineInfo != nil && line[0] == '-' {
+			currentLineInfo.numLines++
+		}
+	}
+	finishHunk()
+
+	return deletedLineInfos
+}
+
+// returns the list of commit hashes that introduced the lines which have now been deleted
+func (self *FixupHelper) blameDeletedLines(deletedLineInfos []*deletedLineInfo) []string {
+	var wg sync.WaitGroup
+	shaChan := make(chan string)
+
+	for _, info := range deletedLineInfos {
+		wg.Add(1)
+		go func(info *deletedLineInfo) {
+			defer wg.Done()
+
+			blameOutput, err := self.c.Git().Blame.BlameLineRange(info.filename, "HEAD", info.startLineIdx, info.numLines)
+			if err != nil {
+				self.c.Log.Errorf("Error blaming file '%s': %v", info.filename, err)
+				return
+			}
+			blameLines := strings.Split(strings.TrimSuffix(blameOutput, "\n"), "\n")
+			for _, line := range blameLines {
+				shaChan <- strings.Split(line, " ")[0]
+			}
+		}(info)
+	}
+
+	go func() {
+		wg.Wait()
+		close(shaChan)
+	}()
+
+	result := set.New[string]()
+	for sha := range shaChan {
+		result.Add(sha)
+	}
+
+	return result.ToSlice()
+}

pkg/gui/controllers/helpers/helpers.go

@@ -33,6 +33,7 @@ type Helpers struct {
 	GPG            *GpgHelper
 	Upstream       *UpstreamHelper
 	AmendHelper    *AmendHelper
+	FixupHelper    *FixupHelper
 	Commits        *CommitsHelper
 	Snake          *SnakeHelper
 	// lives in context package because our contexts need it to render to main
@@ -70,6 +71,7 @@ func NewStubHelpers() *Helpers {
 		GPG:               &GpgHelper{},
 		Upstream:          &UpstreamHelper{},
 		AmendHelper:       &AmendHelper{},
+		FixupHelper:       &FixupHelper{},
 		Commits:           &CommitsHelper{},
 		Snake:             &SnakeHelper{},
 		Diff:              &DiffHelper{},