allow user to discard old file changes for a given commit

11 files changed, 221 insertions, 95 deletions

diff --git a/pkg/commands/errors.go b/pkg/commands/errors.go
new file mode 100644
index 000000000..4723eb95d
--- /dev/null
+++ b/pkg/commands/errors.go
@@ -0,0 +1,14 @@
+package commands
+
+import "github.com/go-errors/errors"
+
+// WrapError wraps an error for the sake of showing a stack trace at the top level
+// the go-errors package, for some reason, does not return nil when you try to wrap
+// a non-error, so we're just doing it here
+func WrapError(err error) error {
+	if err == nil {
+		return err
+	}
+
+	return errors.Wrap(err, 0)
+}
diff --git a/pkg/commands/git.go b/pkg/commands/git.go
index 96b25316c..c4de147cd 100644
--- a/pkg/commands/git.go
+++ b/pkg/commands/git.go
@@ -32,11 +32,11 @@ func navigateToRepoRootDirectory(stat func(string) (os.FileInfo, error), chdir f
 		}
 
 		if !os.IsNotExist(err) {
-			return errors.Wrap(err, 0)
+			return WrapError(err)
 		}
 
 		if err = chdir(".."); err != nil {
-			return errors.Wrap(err, 0)
+			return WrapError(err)
 		}
 	}
 }
@@ -797,10 +797,25 @@ func (c *GitCommand) CherryPickCommits(commits []*Commit) error {
 	return c.OSCommand.RunPreparedCommand(cmd)
 }
 
-// CommitFiles get the specified commit files
-func (c *GitCommand) CommitFiles(commitID string) (string, error) {
+// GetCommitFiles get the specified commit files
+func (c *GitCommand) GetCommitFiles(commitID string) ([]*CommitFile, error) {
 	cmd := fmt.Sprintf("git show --pretty= --name-only %s", commitID)
-	return c.OSCommand.RunCommandWithOutput(cmd)
+	files, err := c.OSCommand.RunCommandWithOutput(cmd)
+	if err != nil {
+		return nil, err
+	}
+
+	commitFiles := make([]*CommitFile, 0)
+
+	for _, file := range strings.Split(strings.TrimRight(files, "\n"), "\n") {
+		commitFiles = append(commitFiles, &CommitFile{
+			Sha:           commitID,
+			Name:          file,
+			DisplayString: file,
+		})
+	}
+
+	return commitFiles, nil
 }
 
 // ShowCommitFile get the diff of specified commit file
@@ -814,3 +829,55 @@ func (c *GitCommand) CheckoutFile(commitSha, fileName string) error {
 	cmd := fmt.Sprintf("git checkout %s %s", commitSha, fileName)
 	return c.OSCommand.RunCommand(cmd)
 }
+
+// DiscardOldFileChanges discards changes to a file from an old commit
+func (c *GitCommand) DiscardOldFileChanges(commits []*Commit, commitIndex int, fileName string) error {
+	// we can make this GPG thing possible it just means we need to do this in two parts:
+	// one where we handle the possibility of a credential request, and the other
+	// where we continue the rebase
+	if c.usingGpg() {
+		errors.New("feature not available for users using GPG")
+	}
+
+	commitSha := commits[commitIndex].Sha
+
+	todo, err := c.GenerateGenericRebaseTodo(commits, commitIndex, "edit")
+	if err != nil {
+		return err
+	}
+
+	cmd, err := c.PrepareInteractiveRebaseCommand(commitSha+"^", todo, true)
+	if err != nil {
+		return err
+	}
+
+	if err := c.OSCommand.RunPreparedCommand(cmd); err != nil {
+		return err
+	}
+
+	// check if file exists in previous commit (this command returns an error if the file doesn't exist)
+	if err := c.OSCommand.RunCommand(fmt.Sprintf("git cat-file -e HEAD^:%s", fileName)); err != nil {
+		if err := c.OSCommand.RemoveFile(fileName); err != nil {
+			return err
+		}
+		if err := c.StageFile(fileName); err != nil {
+			return err
+		}
+	} else {
+		if err := c.CheckoutFile("HEAD^", fileName); err != nil {
+			return err
+		}
+	}
+
+	// amend the commit
+	cmd, err = c.AmendHead()
+	if cmd != nil {
+		errors.New("received unexpected pointer to cmd")
+	}
+	if err != nil {
+		return err
+	}
+
+	// continue
+	return c.GenericMerge("rebase", "continue")
+}
diff --git a/pkg/commands/os.go b/pkg/commands/os.go
index a7a1fdaa4..9e0967cba 100644
--- a/pkg/commands/os.go
+++ b/pkg/commands/os.go
@@ -145,7 +145,7 @@ func sanitisedCommandOutput(output []byte, err error) (string, error) {
 		// errors like 'exit status 1' are not very useful so we'll create an error
 		// from the combined output
 		if outputString == "" {
-			return "", errors.Wrap(err, 0)
+			return "", WrapError(err)
 		}
 		return outputString, errors.New(outputString)
 	}
@@ -224,13 +224,13 @@ func (c *OSCommand) Unquote(message string) string {
 func (c *OSCommand) AppendLineToFile(filename, line string) error {
 	f, err := os.OpenFile(filename, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0600)
 	if err != nil {
-		return errors.Wrap(err, 0)
+		return WrapError(err)
 	}
 	defer f.Close()
 
 	_, err = f.WriteString("\n" + line)
 	if err != nil {
-		return errors.Wrap(err, 0)
+		return WrapError(err)
 	}
 	return nil
 }
@@ -240,16 +240,16 @@ func (c *OSCommand) CreateTempFile(filename, content string) (string, error) {
 	tmpfile, err := ioutil.TempFile("", filename)
 	if err != nil {
 		c.Log.Error(err)
-		return "", errors.Wrap(err, 0)
+		return "", WrapError(err)
 	}
 
 	if _, err := tmpfile.WriteString(content); err != nil {
 		c.Log.Error(err)
-		return "", errors.Wrap(err, 0)
+		return "", WrapError(err)
 	}
 	if err := tmpfile.Close(); err != nil {
 		c.Log.Error(err)
-		return "", errors.Wrap(err, 0)
+		return "", WrapError(err)
 	}
 
 	return tmpfile.Name(), nil
@@ -258,7 +258,7 @@ func (c *OSCommand) CreateTempFile(filename, content string) (string, error) {
 // RemoveFile removes a file at the specified path
 func (c *OSCommand) RemoveFile(filename string) error {
 	err := os.Remove(filename)
-	return errors.Wrap(err, 0)
+	return WrapError(err)
 }
 
 // FileExists checks whether a file exists at the specified path
diff --git a/pkg/gui/commit_files_panel.go b/pkg/gui/commit_files_panel.go
index 1d54a2bcf..7feda9628 100644
--- a/pkg/gui/commit_files_panel.go
+++ b/pkg/gui/commit_files_panel.go
@@ -53,12 +53,49 @@ func (gui *Gui) handleSwitchToCommitsPanel(g *gocui.Gui, v *gocui.View) error {
 }
 
 func (gui *Gui) handleCheckoutCommitFile(g *gocui.Gui, v *gocui.View) error {
-	commitSha := gui.State.Commits[gui.State.Panels.Commits.SelectedLine].Sha
-	fileName := gui.State.CommitFiles[gui.State.Panels.CommitFiles.SelectedLine].Name
+	file := gui.State.CommitFiles[gui.State.Panels.CommitFiles.SelectedLine]
 
-	if err := gui.GitCommand.CheckoutFile(commitSha, fileName); err != nil {
+	if err := gui.GitCommand.CheckoutFile(file.Sha, file.Name); err != nil {
 		return gui.createErrorPanel(gui.g, err.Error())
 	}
 
 	return gui.refreshFiles()
 }
+
+func (gui *Gui) handleDiscardOldFileChange(g *gocui.Gui, v *gocui.View) error {
+	fileName := gui.State.CommitFiles[gui.State.Panels.CommitFiles.SelectedLine].Name
+
+	return gui.createConfirmationPanel(gui.g, v, gui.Tr.SLocalize("DiscardFileChangesTitle"), gui.Tr.SLocalize("DiscardFileChangesPrompt"), func(g *gocui.Gui, v *gocui.View) error {
+		return gui.WithWaitingStatus(gui.Tr.SLocalize("RebasingStatus"), func() error {
+			if err := gui.GitCommand.DiscardOldFileChanges(gui.State.Commits, gui.State.Panels.Commits.SelectedLine, fileName); err != nil {
+				if err := gui.handleGenericMergeCommandResult(err); err != nil {
+					return err
+				}
+			}
+
+			return gui.refreshSidePanels(gui.g)
+		})
+	}, nil)
+}
+
+func (gui *Gui) refreshCommitFilesView() error {
+	commit := gui.getSelectedCommit(gui.g)
+	if commit == nil {
+		return nil
+	}
+
+	files, err := gui.GitCommand.GetCommitFiles(commit.Sha)
+	if err != nil {
+		return gui.createErrorPanel(gui.g, err.Error())
+	}
+
+	gui.State.CommitFiles = files
+
+	gui.refreshSelectedLine(&gui.State.Panels.CommitFiles.SelectedLine, len(gui.State.CommitFiles))
+
+	if err := gui.renderListPanel(gui.getCommitFilesView(), gui.State.CommitFiles); err != nil {
+		return err
+	}
+
+	return gui.handleCommitFileSelect(gui.g, gui.getCommitFilesView())
+}
diff --git a/pkg/gui/commits_panel.go b/pkg/gui/commits_panel.go
index 0de71e875..9b83d725d 100644
--- a/pkg/gui/commits_panel.go
+++ b/pkg/gui/commits_panel.go
@@ -3,7 +3,6 @@ package gui
 import (
 	"fmt"
 	"strconv"
-	"strings"
 
 	"github.com/go-errors/errors"
 
@@ -72,9 +71,12 @@ func (gui *Gui) refreshCommits(g *gocui.Gui) error {
 		fmt.Fprint(v, list)
 
 		gui.refreshStatus(g)
-		if v == g.CurrentView() {
+		if g.CurrentView() == v {
 			gui.handleCommitSelect(g, v)
 		}
+		if g.CurrentView() == gui.getCommitFilesView() {
+			gui.refreshCommitFilesView()
+		}
 		return nil
 	})
 	return nil
@@ -440,36 +442,9 @@ func (gui *Gui) HandlePasteCommits(g *gocui.Gui, v *gocui.View) error {
 }
 
 func (gui *Gui) handleSwitchToCommitFilesPanel(g *gocui.Gui, v *gocui.View) error {
-	commit := gui.getSelectedCommit(g)
-	if commit == nil {
-		return nil
-	}
-
-	commitfileView, err := g.View("commitFiles")
-	if err != nil {
+	if err := gui.refreshCommitFilesView(); err != nil {
 		return err
 	}
 
-	files, err := gui.GitCommand.CommitFiles(commit.Sha)
-	if err != nil {
-		return gui.createErrorPanel(g, err.Error())
-	}
-
-	gui.State.Panels.CommitFiles = &commitFilesPanelState{SelectedLine: 0}
-	gui.State.CommitFiles = make([]*commands.CommitFile, 0)
-
-	if files == "" {
-		gui.State.Panels.CommitFiles.SelectedLine = -1
-	}
-
-	for _, file := range strings.Split(strings.TrimRight(files, "\n"), "\n") {
-		gui.State.CommitFiles = append(gui.State.CommitFiles, &commands.CommitFile{
-			Sha:           commit.Sha,
-			Name:          file,
-			DisplayString: file,
-		})
-	}
-
-	gui.renderListPanel(gui.getCommitFilesView(), gui.State.CommitFiles)
-	return gui.switchFocus(g, v, commitfileView)
+	return gui.switchFocus(g, v, gui.getCommitFilesView())
 }
diff --git a/pkg/gui/gui.go b/pkg/gui/gui.go
index fc40cda07..bd1045105 100644
--- a/pkg/gui/gui.go
+++ b/pkg/gui/gui.go
@@ -155,11 +155,12 @@ func NewGui(log *logrus.Entry, gitCommand *commands.GitCommand, oSCommand *comma
 		StashEntries:        make([]*commands.StashEntry, 0),
 		Platform:            *oSCommand.Platform,
 		Panels: &panelStates{
-			Files:    &filePanelState{SelectedLine: -1},
-			Branches: &branchPanelState{SelectedLine: 0},
-			Commits:  &commitPanelState{SelectedLine: -1},
-			Stash:    &stashPanelState{SelectedLine: -1},
-			Menu:     &menuPanelState{SelectedLine: 0},
+			Files:       &filePanelState{SelectedLine: -1},
+			Branches:    &branchPanelState{SelectedLine: 0},
+			Commits:     &commitPanelState{SelectedLine: -1},
+			CommitFiles: &commitFilesPanelState{SelectedLine: -1},
+			Stash:       &stashPanelState{SelectedLine: -1},
+			Menu:        &menuPanelState{SelectedLine: 0},
 			Merging: &mergingPanelState{
 				ConflictIndex: 0,
 				ConflictTop:   true,
@@ -219,20 +220,21 @@ func max(a, b int) int {
 
 // getFocusLayout returns a manager function for when view gain and lose focus
 func (gui *Gui) getFocusLayout() func(g *gocui.Gui) error {
-	var focusedView *gocui.View
+	var previousView *gocui.View
 	return func(g *gocui.Gui) error {
-		v := gui.g.CurrentView()
-		if v != focusedView {
-			if err := gui.onFocusChange(); err != nil {
-				return err
-			}
-			if err := gui.onFocusLost(focusedView); err != nil {
+		newView := gui.g.CurrentView()
+		if err := gui.onFocusChange(); err != nil {
+			return err
+		}
+		// for now we don't consider losing focus to a popup panel as actually losing focus
+		if newView != previousView && !gui.isPopupPanel(newView.Name()) {
+			if err := gui.onFocusLost(previousView, newView); err != nil {
 				return err
 			}
-			if err := gui.onFocus(v); err != nil {
+			if err := gui.onFocus(newView); err != nil {
 				return err
 			}
-			focusedView = v
+			previousView = newView
 		}
 		return nil
 	}
@@ -246,31 +248,23 @@ func (gui *Gui) onFocusChange() error {
 	return gui.setMainTitle()
 }
 
-func (gui *Gui) onFocusLost(v *gocui.View) error {
+func (gui *Gui) onFocusLost(v *gocui.View, newView *gocui.View) error {
 	if v == nil {
 		return nil
 	}
 	if v.Name() == "branches" {
+		// This stops the branches panel from showing the upstream/downstream changes to the selected branch, when it loses focus
+		// inside renderListPanel it checks to see if the panel has focus
 		if err := gui.renderListPanel(gui.getBranchesView(), gui.State.Branches); err != nil {
 			return err
 		}
 	} else if v.Name() == "main" {
-		// if we have lost focus to a popup panel, that's okay
-		if gui.popupPanelFocused() {
-			return nil
-		}
-
 		// if we have lost focus to a first-class panel, we need to do some cleanup
 		if err := gui.changeContext("main", "normal"); err != nil {
 			return err
 		}
 
 	} else if v.Name() == "commitFiles" {
-		// if we have lost focus to a popup panel, that's okay
-		if gui.popupPanelFocused() {
-			return nil
-		}
-
 		gui.g.SetViewOnBottom(v.Name())
 	}
 	gui.Log.Info(v.Name() + " focus lost")
diff --git a/pkg/gui/keybindings.go b/pkg/gui/keybindings.go
index c5eb758e9..d06280ef0 100644
--- a/pkg/gui/keybindings.go
+++ b/pkg/gui/keybindings.go
@@ -459,10 +459,16 @@ func (gui *Gui) GetInitialKeybindings() []*Binding {
 			Modifier:    gocui.ModNone,
 			Handler:     gui.handleCheckoutCommitFile,
 			Description: gui.Tr.SLocalize("checkoutCommitFile"),
+		}, {
+			ViewName:    "commitFiles",
+			Key:         'd',
+			Modifier:    gocui.ModNone,
+			Handler:     gui.handleDiscardOldFileChange,
+			Description: gui.Tr.SLocalize("discardOldFileChange"),
 		},
 	}
 
-	for _, viewName := range []string{"status", "branches", "files", "commits", "stash", "menu"} {
+	for _, viewName := range []string{"status", "branches", "files", "commits", "commitFiles", "stash", "menu"} {
 		bindings = append(bindings, []*Binding{
 			{ViewName: viewName, Key: gocui.KeyTab, Modifier: gocui.ModNone, Handler: gui.nextView},
 			{ViewName: viewName, Key: gocui.KeyArrowLeft, Modifier: gocui.ModNone, Handler: gui.previousView},
diff --git a/pkg/gui/view_helpers.go b/pkg/gui/view_helpers.go
index eb46a7f8b..372c5d43e 100644
--- a/pkg/gui/view_helpers.go
+++ b/pkg/gui/view_helpers.go
@@ -22,6 +22,11 @@ func (gui *Gui) refreshSidePanels(g *gocui.Gui) error {
 	if err := gui.refreshCommits(g); err != nil {
 		return err
 	}
+
+	if err := gui.refreshCommitFilesView(); err != nil {
+		return err
+	}
+
 	return gui.refreshStashEntries(g)
 }
 
@@ -30,8 +35,13 @@ func (gui *Gui) nextView(g *gocui.Gui, v *gocui.View) error {
 	if v == nil || v.Name() == cyclableViews[len(cyclableViews)-1] {
 		focusedViewName = cyclableViews[0]
 	} else {
+		// if we're in the commitFiles view we'll act like we're in the commits view
+		viewName := v.Name()
+		if viewName == "commitFiles" {
+			viewName = "commits"
+		}
 		for i := range cyclableViews {
-			if v.Name() == cyclableViews[i] {
+			if viewName == cyclableViews[i] {
 				focusedViewName = cyclableViews[i+1]
 				break
 			}
@@ -39,7 +49,7 @@ func (gui *Gui) nextView(g *gocui.Gui, v *gocui.View) error {
 				message := gui.Tr.TemplateLocalize(
 					"IssntListOfViews",
 					Teml{
-						"name": v.Name(),
+						"name": viewName,
 					},
 				)
 				gui.Log.Info(message)
@@ -59,8 +69,13 @@ func (gui *Gui) previousView(g *gocui.Gui, v *gocui.View) error {
 	if v == nil || v.Name() == cyclableViews[0] {
 		focusedViewName = cyclableViews[len(cyclableViews)-1]
 	} else {
+		// if we're in the commitFiles view we'll act like we're in the commits view
+		viewName := v.Name()
+		if viewName == "commitFiles" {
+			viewName = "commits"
+		}
 		for i := range cyclableViews {
-			if v.Name() == cyclableViews[i] {
+			if viewName == cyclableViews[i] {
 				focusedViewName = cyclableViews[i-1] // TODO: make this work properly
 				break
 			}
@@ -68,7 +83,7 @@ func (gui *Gui) previousView(g *gocui.Gui, v *gocui.View) error {
 				message := gui.Tr.TemplateLocalize(
 					"IssntListOfViews",
 					Teml{
-						"name": v.Name(),
+						"name": viewName,
 					},
 				)
 				gui.Log.Info(message)
@@ -131,15 +146,10 @@ func (gui *Gui) returnFocus(g *gocui.Gui, v *gocui.View) error {
 // pass in oldView = nil if you don't want to be able to return to your old view
 // TODO: move some of this logic into our onFocusLost and onFocus hooks
 func (gui *Gui) switchFocus(g *gocui.Gui, oldView, newView *gocui.View) error {
-	// we assume we'll never want to return focus to a confirmation panel i.e.
-	// we should never stack confirmation panels
-	if oldView != nil && oldView.Name() != "confirmation" {
-		// second class panels should never have focus restored to them because
-		// once they lose focus they are effectively 'destroyed'
-		secondClassPanels := []string{"confirmation", "menu"}
-		if !utils.IncludesString(secondClassPanels, oldView.Name()) {
-			gui.State.PreviousView = oldView.Name()
-		}
+	// we assume we'll never want to return focus to a popup panel i.e.
+	// we should never stack popup panels
+	if oldView != nil && !gui.isPopupPanel(oldView.Name()) {
+		gui.State.PreviousView = oldView.Name()
 	}
 
 	gui.Log.Info("setting highlight to true for view" + newView.Name())
@@ -301,7 +311,7 @@ func (gui *Gui) currentViewName() string {
 
 func (gui *Gui) resizeCurrentPopupPanel(g *gocui.Gui) error {
 	v := g.CurrentView()
-	if v.Name() == "commitMessage" || v.Name() == "credentials" || v.Name() == "confirmation" {
+	if gui.isPopupPanel(v.Name()) {
 		return gui.resizePopupPanel(g, v)
 	}
 	return nil
@@ -393,14 +403,10 @@ func (gui *Gui) handleFocusView(g *gocui.Gui, v *gocui.View) error {
 	return err
 }
 
+func (gui *Gui) isPopupPanel(viewName string) bool {
+	return viewName == "commitMessage" || viewName == "credentials" || viewName == "confirmation" || viewName == "menu"
+}
+
 func (gui *Gui) popupPanelFocused() bool {
-	viewNames := []string{"commitMessage",
-		"credentials",
-		"menu"}
-	for _, viewName := range viewNames {
-		if gui.currentViewName() == viewName {
-			return true
-		}
-	}
-	return false
+	return gui.isPopupPanel(gui.currentViewName())
 }
diff --git a/pkg/i18n/dutch.go b/pkg/i18n/dutch.go
index 4d2ee4236..13eb1ee0c 100644
--- a/pkg/i18n/dutch.go
+++ b/pkg/i18n/dutch.go
@@ -658,6 +658,15 @@ func addDutch(i18nObject *i18n.Bundle) error {
 		}, &i18n.Message{
 			ID:    "checkoutCommitFile",
 			Other: "checkout file",
+		}, &i18n.Message{
+			ID:    "discardOldFileChange",
+			Other: "discard this commit's changes to this file",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesTitle",
+			Other: "Discard file changes",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesPrompt",
+			Other: "Are you sure you want to discard this commit's changes to this file? If this file was created in this commit, it will be deleted",
 		},
 	)
 }
diff --git a/pkg/i18n/english.go b/pkg/i18n/english.go
index c9eda4ce6..925b9db38 100644
--- a/pkg/i18n/english.go
+++ b/pkg/i18n/english.go
@@ -681,6 +681,15 @@ func addEnglish(i18nObject *i18n.Bundle) error {
 		}, &i18n.Message{
 			ID:    "checkoutCommitFile",
 			Other: "checkout file",
+		}, &i18n.Message{
+			ID:    "discardOldFileChange",
+			Other: "discard this commit's changes to this file",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesTitle",
+			Other: "Discard file changes",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesPrompt",
+			Other: "Are you sure you want to discard this commit's changes to this file? If this file was created in this commit, it will be deleted",
 		},
 	)
 }
diff --git a/pkg/i18n/polish.go b/pkg/i18n/polish.go
index 30462a7c3..37791d9e5 100644
--- a/pkg/i18n/polish.go
+++ b/pkg/i18n/polish.go
@@ -641,6 +641,15 @@ func addPolish(i18nObject *i18n.Bundle) error {
 		}, &i18n.Message{
 			ID:    "checkoutCommitFile",
 			Other: "checkout file",
+		}, &i18n.Message{
+			ID:    "discardOldFileChange",
+			Other: "discard this commit's changes to this file",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesTitle",
+			Other: "Discard file changes",
+		}, &i18n.Message{
+			ID:    "DiscardFileChangesPrompt",
+			Other: "Are you sure you want to discard this commit's changes to this file? If this file was created in this commit, it will be deleted",
 		},
 	)
 }