Expose {{.SelectedCommitRange}} to custom commands (#4204)

- **PR Description**

Expose `{{.SelectedCommitRange}}` to custom commands. It has fields .To
and .From (the hashes of the last and the first selected commits,
respectively), and it is useful for creating git commands that act on a
range of commits.

Fixes #4184.

- **Please check if the PR fulfills these requirements**

* [x] Cheatsheets are up-to-date (run `go generate ./...`)
* [x] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [x] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [x] Docs have been updated if necessary
* [x] You've read through your own file changes for silly mistakes etc

docs/Custom_Command_Keybindings.md

@@ -297,6 +297,7 @@ Your commands can contain placeholder strings using Go's [template syntax](https
 
 ```
 SelectedCommit
+SelectedCommitRange
 SelectedFile
 SelectedPath
 SelectedLocalBranch
@@ -314,6 +315,11 @@ CheckedOutBranch
 
 To see what fields are available on e.g. the `SelectedFile`, see [here](https://github.com/jesseduffield/lazygit/blob/master/pkg/gui/services/custom_commands/models.go) (all the modelling lives in the same file).
 
+We don't support accessing all elements of a range selection yet. We might add this in the future, but as a special case you can access the range of selected commits by using `SelectedCommitRange`, which has two properties `.To` and `.From` which are the hashes of the bottom and top selected commits, respectively. This is useful for passing them to a git command that operates on a range of commits. For example, to create patches for all selected commits, you might use
+```yml
+  command: "git format-patch {{.SelectedCommitRange.From}}^..{{.SelectedCommitRange.To}}"
+```
+
 ## Keybinding collisions
 
 If your custom keybinding collides with an inbuilt keybinding that is defined for the same context, only the custom keybinding will be executed. This also applies to the global context. However, one caveat is that if you have a custom keybinding defined on the global context for some key, and there is an in-built keybinding defined for the same key and for a specific context (say the 'files' context), then the in-built keybinding will take precedence. See how to change in-built keybindings [here](https://github.com/jesseduffield/lazygit/blob/master/docs/Config.md#keybindings)

pkg/gui/services/custom_commands/session_state_loader.go

@@ -162,12 +162,29 @@ func worktreeShimFromModelRemote(worktree *models.Worktree) *Worktree {
 	}
 }
 
+type CommitRange struct {
+	From string
+	To   string
+}
+
+func makeCommitRange(commits []*models.Commit, _ int, _ int) *CommitRange {
+	if len(commits) == 0 {
+		return nil
+	}
+
+	return &CommitRange{
+		From: commits[len(commits)-1].Hash,
+		To:   commits[0].Hash,
+	}
+}
+
 // SessionState captures the current state of the application for use in custom commands
 type SessionState struct {
 	SelectedLocalCommit    *Commit // deprecated, use SelectedCommit
 	SelectedReflogCommit   *Commit // deprecated, use SelectedCommit
 	SelectedSubCommit      *Commit // deprecated, use SelectedCommit
 	SelectedCommit         *Commit
+	SelectedCommitRange    *CommitRange
 	SelectedFile           *File
 	SelectedPath           string
 	SelectedLocalBranch    *Branch
@@ -183,14 +200,20 @@ type SessionState struct {
 
 func (self *SessionStateLoader) call() *SessionState {
 	selectedLocalCommit := commitShimFromModelCommit(self.c.Contexts().LocalCommits.GetSelected())
+	selectedLocalCommitRange := makeCommitRange(self.c.Contexts().LocalCommits.GetSelectedItems())
 	selectedReflogCommit := commitShimFromModelCommit(self.c.Contexts().ReflogCommits.GetSelected())
+	selectedReflogCommitRange := makeCommitRange(self.c.Contexts().ReflogCommits.GetSelectedItems())
 	selectedSubCommit := commitShimFromModelCommit(self.c.Contexts().SubCommits.GetSelected())
+	selectedSubCommitRange := makeCommitRange(self.c.Contexts().SubCommits.GetSelectedItems())
 
 	selectedCommit := selectedLocalCommit
+	selectedCommitRange := selectedLocalCommitRange
 	if self.c.Context().IsCurrentOrParent(self.c.Contexts().ReflogCommits) {
 		selectedCommit = selectedReflogCommit
+		selectedCommitRange = selectedReflogCommitRange
 	} else if self.c.Context().IsCurrentOrParent(self.c.Contexts().SubCommits) {
 		selectedCommit = selectedSubCommit
+		selectedCommitRange = selectedSubCommitRange
 	}
 
 	selectedPath := self.c.Contexts().Files.GetSelectedPath()
@@ -207,6 +230,7 @@ func (self *SessionStateLoader) call() *SessionState {
 		SelectedReflogCommit:   selectedReflogCommit,
 		SelectedSubCommit:      selectedSubCommit,
 		SelectedCommit:         selectedCommit,
+		SelectedCommitRange:    selectedCommitRange,
 		SelectedLocalBranch:    branchShimFromModelBranch(self.c.Contexts().Branches.GetSelected()),
 		SelectedRemoteBranch:   remoteBranchShimFromModelRemoteBranch(self.c.Contexts().RemoteBranches.GetSelected()),
 		SelectedRemote:         remoteShimFromModelRemote(self.c.Contexts().Remotes.GetSelected()),

pkg/integration/tests/custom_commands/selected_commit_range.go

@@ -0,0 +1,41 @@
+package custom_commands
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var SelectedCommitRange = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Use the {{ .SelectedCommitRange }} template variable",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupRepo: func(shell *Shell) {
+		shell.CreateNCommits(3)
+	},
+	SetupConfig: func(cfg *config.AppConfig) {
+		cfg.GetUserConfig().CustomCommands = []config.CustomCommand{
+			{
+				Key:     "X",
+				Context: "global",
+				Command: `git log --format="%s" {{.SelectedCommitRange.From}}^..{{.SelectedCommitRange.To}} > file.txt`,
+			},
+		}
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().Focus().
+			Lines(
+				Contains("commit 03").IsSelected(),
+				Contains("commit 02"),
+				Contains("commit 01"),
+			)
+
+		t.GlobalPress("X")
+		t.FileSystem().FileContent("file.txt", Equals("commit 03\n"))
+
+		t.Views().Commits().Focus().
+			Press(keys.Universal.RangeSelectDown)
+
+		t.GlobalPress("X")
+		t.FileSystem().FileContent("file.txt", Equals("commit 03\ncommit 02\n"))
+	},
+})

pkg/integration/tests/test_list.go

@@ -139,6 +139,7 @@ var tests = []*components.IntegrationTest{
 	custom_commands.MultipleContexts,
 	custom_commands.MultiplePrompts,
 	custom_commands.SelectedCommit,
+	custom_commands.SelectedCommitRange,
 	custom_commands.SelectedPath,
 	custom_commands.ShowOutputInPanel,
 	custom_commands.SuggestionsCommand,