Refactor repo_paths.go to use git rev-parse

This changes GetRepoPaths() to pull information from `git rev-parse`
instead of effectively reimplementing git's logic for pathfinding. This
change fixes issues with bare repos, esp. versioned homedir use cases,
by aligning lazygit's path handling to what git itself does.

This change also enables lazygit to run from arbitrary subdirectories of
a repository, including correct handling of symlinks, including "deep"
symlinks into a repo, worktree, a repo's submodules, etc.

Integration tests are now resilient against unintended side effects from
the host's environment variables. Of necessity, $PATH and $TERM are the
only env vars allowed through now.

pkg/commands/git_commands/worktree_loader.go

@@ -4,6 +4,7 @@ import (
 	iofs "io/fs"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/go-errors/errors"
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
@@ -57,18 +58,14 @@ func (self *WorktreeLoader) GetWorktrees() ([]*models.Worktree, error) {
 			isCurrent := path == worktreePath
 			isPathMissing := self.pathExists(path)
 
-			var gitDir string
-			gitDir, err := getWorktreeGitDirPath(self.Fs, path)
-			if err != nil {
-				self.Log.Warnf("Could not find git dir for worktree %s: %v", path, err)
-			}
-
 			current = &models.Worktree{
 				IsMain:        isMain,
 				IsCurrent:     isCurrent,
 				IsPathMissing: isPathMissing,
 				Path:          path,
-				GitDir:        gitDir,
+				// we defer populating GitDir until a loop below so that
+				// we can parallelize the calls to git rev-parse
+				GitDir: "",
 			}
 		} else if strings.HasPrefix(splitLine, "branch ") {
 			branch := strings.SplitN(splitLine, " ", 2)[1]
@@ -76,6 +73,28 @@ func (self *WorktreeLoader) GetWorktrees() ([]*models.Worktree, error) {
 		}
 	}
 
+	wg := sync.WaitGroup{}
+	wg.Add(len(worktrees))
+	for _, worktree := range worktrees {
+		worktree := worktree
+
+		go utils.Safe(func() {
+			defer wg.Done()
+
+			if worktree.IsPathMissing {
+				return
+			}
+			gitDir, err := callGitRevParseWithDir(self.cmd, self.version, worktree.Path, "--absolute-git-dir")
+			if err != nil {
+				self.Log.Warnf("Could not find git dir for worktree %s: %v", worktree.Path, err)
+				return
+			}
+
+			worktree.GitDir = gitDir
+		})
+	}
+	wg.Wait()
+
 	names := getUniqueNamesFromPaths(lo.Map(worktrees, func(worktree *models.Worktree, _ int) string {
 		return worktree.Path
 	}))