Add coauthor (#2)

Add co-author to commits

Add addCoAuthor command for commits

- Implement the `addCoAuthor` command to add co-authors to commits.
- Utilize suggestions helpers to populate author names from the suggestions list.
- Added command to gui at `LocalCommitsController`.

This commit introduces the `addCoAuthor` command, which allows users to easily add co-authors to their commits. The co-author names are populated from the suggestions list, minimizing the chances of user input errors. The co-authors are added using the Co-authored-by metadata format recognized by GitHub and GitLab.

pkg/integration/tests/commit/add_co_author.go

@@ -0,0 +1,40 @@
+package commit
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var AddCoAuthor = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Add co-author on a commit",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("initial commit")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("initial commit").IsSelected(),
+			).
+			Press(keys.Commits.ResetCommitAuthor).
+			Tap(func() {
+				t.ExpectPopup().Menu().
+					Title(Equals("Amend commit attribute")).
+					Select(Contains("Add co-author")).
+					Confirm()
+
+				t.ExpectPopup().Prompt().
+					Title(Contains("Add co-author")).
+					Type("John Smith <jsmith@gmail.com>").
+					Confirm()
+			})
+
+		t.Views().Main().ContainsLines(
+			Contains("initial commit"),
+			Contains("Co-authored-by: John Smith <jsmith@gmail.com>"),
+		)
+	},
+})