Add SelectedSubmodule to SessionState

Introduce the 'SelectedSubmodule' struct and allow using it as a
placeholder value.
Add a corresponding test.
Update the documentation to include it among the listed placeholder
values.

docs-master/Custom_Command_Keybindings.md

@@ -299,6 +299,7 @@ SelectedCommit
 SelectedCommitRange
 SelectedFile
 SelectedPath
+SelectedSubmodule
 SelectedLocalBranch
 SelectedRemoteBranch
 SelectedRemote

pkg/gui/services/custom_commands/models.go

@@ -43,6 +43,12 @@ type File struct {
 	IsWorktree              bool
 }
 
+type Submodule struct {
+	Name string
+	Path string
+	Url  string
+}
+
 type Branch struct {
 	Name           string
 	DisplayName    string

pkg/gui/services/custom_commands/session_state_loader.go

@@ -62,6 +62,18 @@ func fileShimFromModelFile(file *models.File) *File {
 	}
 }
 
+func submoduleShimFromModelSubmodule(submodule *models.SubmoduleConfig) *Submodule {
+	if submodule == nil {
+		return nil
+	}
+
+	return &Submodule{
+		Name: submodule.Name,
+		Path: submodule.Path,
+		Url:  submodule.Url,
+	}
+}
+
 func branchShimFromModelBranch(branch *models.Branch) *Branch {
 	if branch == nil {
 		return nil
@@ -186,6 +198,7 @@ type SessionState struct {
 	SelectedCommit         *Commit
 	SelectedCommitRange    *CommitRange
 	SelectedFile           *File
+	SelectedSubmodule      *Submodule
 	SelectedPath           string
 	SelectedLocalBranch    *Branch
 	SelectedRemoteBranch   *RemoteBranch
@@ -225,6 +238,7 @@ func (self *SessionStateLoader) call() *SessionState {
 
 	return &SessionState{
 		SelectedFile:           fileShimFromModelFile(self.c.Contexts().Files.GetSelectedFile()),
+		SelectedSubmodule:      submoduleShimFromModelSubmodule(self.c.Contexts().Submodules.GetSelected()),
 		SelectedPath:           selectedPath,
 		SelectedLocalCommit:    selectedLocalCommit,
 		SelectedReflogCommit:   selectedReflogCommit,

pkg/integration/tests/custom_commands/selected_submodule.go

@@ -0,0 +1,52 @@
+package custom_commands
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var SelectedSubmodule = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Use the {{ .SelectedSubmodule }} template variable",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("Initial commit")
+		shell.CloneIntoSubmodule("submodule", "path/submodule")
+		shell.Commit("Add submodule")
+	},
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().CustomCommands = []config.CustomCommand{
+			{
+				Key:     "X",
+				Context: "submodules",
+				Command: "printf '%s' '{{ .SelectedSubmodule.Path }}' > file.txt",
+			},
+			{
+				Key:     "U",
+				Context: "submodules",
+				Command: "printf '%s' '{{ .SelectedSubmodule.Url }}' > file.txt",
+			},
+			{
+				Key:     "N",
+				Context: "submodules",
+				Command: "printf '%s' '{{ .SelectedSubmodule.Name }}' > file.txt",
+			},
+		}
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Submodules().
+			Focus().
+			Lines(
+				Contains("submodule").IsSelected(),
+			)
+
+		t.Views().Submodules().Press("X")
+		t.FileSystem().FileContent("file.txt", Equals("path/submodule"))
+
+		t.Views().Submodules().Press("U")
+		t.FileSystem().FileContent("file.txt", Equals("../submodule"))
+
+		t.Views().Submodules().Press("N")
+		t.FileSystem().FileContent("file.txt", Equals("submodule"))
+	},
+})

pkg/integration/tests/test_list.go

@@ -178,6 +178,7 @@ var tests = []*components.IntegrationTest{
 	custom_commands.SelectedCommit,
 	custom_commands.SelectedCommitRange,
 	custom_commands.SelectedPath,
+	custom_commands.SelectedSubmodule,
 	custom_commands.ShowOutputInPanel,
 	custom_commands.SuggestionsCommand,
 	custom_commands.SuggestionsPreset,