Support bare worktrees where worktree does not have its own .git file

This was on oversight on my part: I assumed that the --work-tree arg was
always intended for use with linked worktrees which have a .git file
pointing back to the repo.

I'm honestly confused now: seems like there are three kinds of worktrees:
* the main worktree of a non-bare repo
* a linked worktree (with its own gitdir in the repo's worktrees/ dir)
* a random folder which you specify as a worktree with the --work-tree arg

I'm pretty sure the --work-tree arg is only intended to be used with this
third kind or workree

pkg/commands/git_commands/repo_paths.go

@@ -91,10 +91,24 @@ func getRepoPathsAux(
 	if err != nil {
 		return nil, errors.Errorf("failed to get repo git dir path: %v", err)
 	}
-	worktreeGitDirPath, err := worktreeGitDirPath(fs, currentPath)
-	if err != nil {
-		return nil, errors.Errorf("failed to get worktree git dir path: %v", err)
+
+	var worktreeGitDirPath string
+	if env.GetWorkTreeEnv() != "" {
+		// This env is set when you pass --work-tree to lazygit. In that case,
+		// we're not dealing with a linked work-tree, we're dealing with a 'specified'
+		// worktree (for lack of a better term). In this case, the worktree has no
+		// .git file and it just contains a bunch of files: it has no idea it's
+		// pointed to by a bare repo. As such it does not have its own git dir within
+		// the bare repo's git dir. Instead, we just use the bare repo's git dir.
+		worktreeGitDirPath = repoGitDirPath
+	} else {
+		var err error
+		worktreeGitDirPath, err = getWorktreeGitDirPath(fs, currentPath)
+		if err != nil {
+			return nil, errors.Errorf("failed to get worktree git dir path: %v", err)
+		}
 	}
+
 	repoName := path.Base(repoPath)
 
 	return &RepoPaths{
@@ -110,7 +124,7 @@ func getRepoPathsAux(
 // Returns the path of the git-dir for the worktree. For linked worktrees, the worktree has
 // a .git file that points to the git-dir (which itself lives in the git-dir
 // of the repo)
-func worktreeGitDirPath(fs afero.Fs, worktreePath string) (string, error) {
+func getWorktreeGitDirPath(fs afero.Fs, worktreePath string) (string, error) {
 	// if .git is a file, we're in a linked worktree, otherwise we're in
 	// the main worktree
 	dotGitPath := path.Join(worktreePath, ".git")

pkg/commands/git_commands/worktree_loader.go

@@ -58,7 +58,7 @@ func (self *WorktreeLoader) GetWorktrees() ([]*models.Worktree, error) {
 			isPathMissing := self.pathExists(path)
 
 			var gitDir string
-			gitDir, err := worktreeGitDirPath(self.Fs, path)
+			gitDir, err := getWorktreeGitDirPath(self.Fs, path)
 			if err != nil {
 				self.Log.Warnf("Could not find git dir for worktree %s: %v", path, err)
 			}