Add command to find base commit for creating a fixup

docs/Config.md

@@ -209,6 +209,7 @@ keybinding:
     commitChangesWithoutHook: 'w' # commit changes without pre-commit hook
     amendLastCommit: 'A'
     commitChangesWithEditor: 'C'
+    findBaseCommitForFixup: '<c-f>'
     confirmDiscard: 'x'
     ignoreFile: 'i'
     refreshFiles: 'r'

docs/Fixup_Commits.md

@@ -0,0 +1,64 @@
+# Fixup Commits
+
+## Background
+
+There's this common scenario that you have a PR in review, the reviewer is
+requesting some changes, and you make those changes and would normally simply
+squash them into the original commit that they came from. If you do that,
+however, there's no way for the reviewer to see what you changed. You could just
+make a separate commit with those changes at the end of the branch, but this is
+not ideal because it results in a git history that is not very clean.
+
+To help with this, git has a concept of fixup commits: you do make a separate
+commit, but the subject of this commit is the string "fixup! " followed by the
+original commit subject. This both tells the reviewer what's going on (you are
+making a change that you later will squash into the designated commit), and it
+provides an easy way to actually perform this squash operation when you are
+ready to do that (before merging).
+
+## Creating fixup commits
+
+You could of course create fixup commits manually by typing in the commit
+message with the prefix yourself. But lazygit has an easier way to do that:
+in the Commits view, select the commit that you want to create a fixup for, and
+press shift-F (for "Create fixup commit for this commit"). This automatically
+creates a commit with the appropriate subject line.
+
+Don't confuse this with the lowercase "f" command ("Fixup commit"); that one
+squashes the selected commit into its parent, this is not what we want here.
+
+## Squashing fixup commits
+
+When you're ready to merge the branch and want to squash all these fixup commits
+that you created, that's very easy to do: select the first commit of your branch
+and hit shift-S (for "Squash all 'fixup!' commits above selected commit
+(autosquash)"). Boom, done.
+
+## Finding the commit to create a fixup for
+
+When you are making changes to code that you changed earlier in a long branch,
+it can be tedious to find the commit to squash it into. Lazygit has a command to
+help you with this, too: in the Files view, press ctrl-f to select the right
+base commit in the Commits view automatically. From there, you can either press
+shift-F to create a fixup commit for it, or shift-A to amend your changes into
+the commit if you haven't published your branch yet.
+
+This command works in many cases, and when it does it almost feels like magic,
+but it's important to understand its limitations because it doesn't always work.
+The way it works is that it looks at the deleted lines of your current
+modifications, blames them to find out which commit those lines come from, and
+if they all come from the same commit, it selects it. So here are cases where it
+doesn't work:
+
+- Your current diff has only added lines, but no deleted lines. In this case
+  there's no way for lazygit to know which commit you want to add them to.
+- The deleted lines belong to multiple different commits. In this case you can
+  help lazygit by staging a set of files or hunks that all belong to the same
+  commit; if some changes are staged, the ctrl-f command works only on those.
+- The found commit is already on master; in this case, lazygit refuses to select
+  it, because it doesn't make sense to create fixups for it, let alone amend to
+  it.
+
+To sum it up: the command works great if you are changing code again that you
+changed or added earlier in the same branch. This is a common enough case to
+make the command useful.

docs/keybindings/Keybindings_en.md

@@ -123,6 +123,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: Commit changes without pre-commit hook
   <kbd>A</kbd>: Amend last commit
   <kbd>C</kbd>: Commit changes using git editor
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: Edit file
   <kbd>o</kbd>: Open file
   <kbd>i</kbd>: Ignore or exclude file

docs/keybindings/Keybindings_ja.md

@@ -196,6 +196,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: pre-commitフックを実行せずに変更をコミット
   <kbd>A</kbd>: 最新のコミットにamend
   <kbd>C</kbd>: gitエディタを使用して変更をコミット
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: ファイルを編集
   <kbd>o</kbd>: ファイルを開く
   <kbd>i</kbd>: ファイルをignore

docs/keybindings/Keybindings_ko.md

@@ -336,6 +336,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: Commit changes without pre-commit hook
   <kbd>A</kbd>: 마지맛 커밋 수정
   <kbd>C</kbd>: Git 편집기를 사용하여 변경 내용을 커밋합니다.
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: 파일 편집
   <kbd>o</kbd>: 파일 닫기
   <kbd>i</kbd>: Ignore file

docs/keybindings/Keybindings_nl.md

@@ -56,6 +56,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: Commit veranderingen zonder pre-commit hook
   <kbd>A</kbd>: Wijzig laatste commit
   <kbd>C</kbd>: Commit veranderingen met de git editor
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: Verander bestand
   <kbd>o</kbd>: Open bestand
   <kbd>i</kbd>: Ignore or exclude file

docs/keybindings/Keybindings_pl.md

@@ -157,6 +157,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: Zatwierdź zmiany bez skryptu pre-commit
   <kbd>A</kbd>: Zmień ostatni commit
   <kbd>C</kbd>: Zatwierdź zmiany używając edytora
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: Edytuj plik
   <kbd>o</kbd>: Otwórz plik
   <kbd>i</kbd>: Ignore or exclude file

docs/keybindings/Keybindings_ru.md

@@ -330,6 +330,7 @@ _Связки клавиш_
   <kbd>w</kbd>: Закоммитить изменения без предварительного хука коммита
   <kbd>A</kbd>: Правка последнего коммита
   <kbd>C</kbd>: Сохранить изменения с помощью редактора git
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: Редактировать файл
   <kbd>o</kbd>: Открыть файл
   <kbd>i</kbd>: Игнорировать или исключить файл

docs/keybindings/Keybindings_zh-CN.md

@@ -204,6 +204,7 @@ _Legend: `<c-b>` means ctrl+b, `<a-b>` means alt+b, `B` means shift+b_
   <kbd>w</kbd>: 提交更改而无需预先提交钩子
   <kbd>A</kbd>: 修补最后一次提交
   <kbd>C</kbd>: 提交更改（使用编辑器编辑提交信息）
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: 编辑文件
   <kbd>o</kbd>: 打开文件
   <kbd>i</kbd>: 忽略文件

docs/keybindings/Keybindings_zh-TW.md

@@ -299,6 +299,7 @@ _說明：`<c-b>` 表示 Ctrl+B、`<a-b>` 表示 Alt+B，`B`表示 Shift+B_
   <kbd>w</kbd>: 沒有預提交 hook 就提交更改
   <kbd>A</kbd>: 修正上次提交
   <kbd>C</kbd>: 使用 git 編輯器提交變更
+  <kbd>&lt;c-f&gt;</kbd>: Find base commit for fixup
   <kbd>e</kbd>: 編輯檔案
   <kbd>o</kbd>: 開啟檔案
   <kbd>i</kbd>: 忽略或排除檔案

pkg/commands/git.go

@@ -21,6 +21,7 @@ import (
 
 // GitCommand is our main git interface
 type GitCommand struct {
+	Blame       *git_commands.BlameCommands
 	Branch      *git_commands.BranchCommands
 	Commit      *git_commands.CommitCommands
 	Config      *git_commands.ConfigCommands
@@ -160,6 +161,7 @@ func NewGitCommandAux(
 	patchCommands := git_commands.NewPatchCommands(gitCommon, rebaseCommands, commitCommands, statusCommands, stashCommands, patchBuilder)
 	bisectCommands := git_commands.NewBisectCommands(gitCommon)
 	worktreeCommands := git_commands.NewWorktreeCommands(gitCommon)
+	blameCommands := git_commands.NewBlameCommands(gitCommon)
 
 	branchLoader := git_commands.NewBranchLoader(cmn, cmd, branchCommands.CurrentBranchInfo, configCommands)
 	commitFileLoader := git_commands.NewCommitFileLoader(cmn, cmd)
@@ -171,6 +173,7 @@ func NewGitCommandAux(
 	tagLoader := git_commands.NewTagLoader(cmn, cmd)
 
 	return &GitCommand{
+		Blame:       blameCommands,
 		Branch:      branchCommands,
 		Commit:      commitCommands,
 		Config:      configCommands,

pkg/commands/git_commands/blame.go

@@ -0,0 +1,33 @@
+package git_commands
+
+import (
+	"fmt"
+)
+
+type BlameCommands struct {
+	*GitCommon
+}
+
+func NewBlameCommands(gitCommon *GitCommon) *BlameCommands {
+	return &BlameCommands{
+		GitCommon: gitCommon,
+	}
+}
+
+// Blame a range of lines. For each line, output the hash of the commit where
+// the line last changed, then a space, then a description of the commit (author
+// and date), another space, and then the line. For example:
+//
+//	ac90ebac688fe8bc2ffd922157a9d2c54681d2aa (Stefan Haller 2023-08-01 14:54:56 +0200 11) func NewBlameCommands(gitCommon *GitCommon) *BlameCommands {
+//	ac90ebac688fe8bc2ffd922157a9d2c54681d2aa (Stefan Haller 2023-08-01 14:54:56 +0200 12) 	return &BlameCommands{
+//	ac90ebac688fe8bc2ffd922157a9d2c54681d2aa (Stefan Haller 2023-08-01 14:54:56 +0200 13) 		GitCommon: gitCommon,
+func (self *BlameCommands) BlameLineRange(filename string, commit string, firstLine int, numLines int) (string, error) {
+	cmdArgs := NewGitCmd("blame").
+		Arg("-l").
+		Arg(fmt.Sprintf("-L%d,+%d", firstLine, numLines)).
+		Arg(commit).
+		Arg("--").
+		Arg(filename)
+
+	return self.cmd.New(cmdArgs.ToArgv()).RunWithOutput()
+}

pkg/commands/git_commands/commit.go

@@ -198,6 +198,20 @@ func (self *CommitCommands) GetCommitMessagesFirstLine(shas []string) (string, e
 	return self.cmd.New(cmdArgs).DontLog().RunWithOutput()
 }
 
+// Example output:
+//
+//	cd50c79ae Preserve the commit message correctly even if the description has blank lines
+//	3ebba5f32 Add test demonstrating a bug with preserving the commit message
+//	9a423c388 Remove unused function
+func (self *CommitCommands) GetShasAndCommitMessagesFirstLine(shas []string) (string, error) {
+	cmdArgs := NewGitCmd("show").
+		Arg("--no-patch", "--pretty=format:%h %s").
+		Arg(shas...).
+		ToArgv()
+
+	return self.cmd.New(cmdArgs).DontLog().RunWithOutput()
+}
+
 func (self *CommitCommands) GetCommitsOneline(shas []string) (string, error) {
 	cmdArgs := NewGitCmd("show").
 		Arg("--no-patch", "--oneline").

pkg/commands/git_commands/diff.go

@@ -78,3 +78,11 @@ func (self *DiffCommands) OpenDiffToolCmdObj(opts DiffToolCmdOptions) oscommands
 		Arg("--", opts.Filepath).
 		ToArgv())
 }
+
+func (self *DiffCommands) DiffIndexCmdObj(diffArgs ...string) oscommands.ICmdObj {
+	return self.cmd.New(
+		NewGitCmd("diff-index").
+			Arg("--submodule", "--no-ext-diff", "--no-color", "--patch").
+			Arg(diffArgs...).ToArgv(),
+	)
+}

pkg/config/user_config.go

@@ -366,6 +366,7 @@ type KeybindingFilesConfig struct {
 	CommitChangesWithoutHook string `yaml:"commitChangesWithoutHook"`
 	AmendLastCommit          string `yaml:"amendLastCommit"`
 	CommitChangesWithEditor  string `yaml:"commitChangesWithEditor"`
+	FindBaseCommitForFixup   string `yaml:"findBaseCommitForFixup"`
 	ConfirmDiscard           string `yaml:"confirmDiscard"`
 	IgnoreFile               string `yaml:"ignoreFile"`
 	RefreshFiles             string `yaml:"refreshFiles"`
@@ -762,6 +763,7 @@ func GetDefaultConfig() *UserConfig {
 				CommitChangesWithoutHook: "w",
 				AmendLastCommit:          "A",
 				CommitChangesWithEditor:  "C",
+				FindBaseCommitForFixup:   "<c-f>",
 				IgnoreFile:               "i",
 				RefreshFiles:             "r",
 				StashAllChanges:          "s",

pkg/gui/controllers.go

@@ -103,6 +103,7 @@ func (gui *Gui) resetHelpersAndControllers() {
 		CherryPick:      cherryPickHelper,
 		Upstream:        helpers.NewUpstreamHelper(helperCommon, suggestionsHelper.GetRemoteBranchesSuggestionsFunc),
 		AmendHelper:     helpers.NewAmendHelper(helperCommon, gpgHelper),
+		FixupHelper:     helpers.NewFixupHelper(helperCommon),
 		Commits:         commitsHelper,
 		Snake:           helpers.NewSnakeHelper(helperCommon),
 		Diff:            diffHelper,

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),