Preliminary fix and debug information to investigate panic

src/git/backend_commands.go

@@ -126,13 +126,26 @@ func ParseVerboseBranchesOutput(output string) (domain.BranchInfos, domain.Local
 	lines := stringslice.Lines(output)
 	checkedoutBranch := domain.EmptyLocalBranchName()
 	for _, line := range lines {
-		if line == "" {
+		if strings.TrimSpace(line) == "" {
 			continue
 		}
 		parts := spaceRE.Split(line[2:], 3)
 		if parts[0] == "remotes/origin/HEAD" {
 			continue
 		}
+		if len(parts) < 2 {
+			// This shouldn't happen, but did happen in https://github.com/git-town/git-town/issues/2562.
+			fmt.Println("ERROR: Encountered irregular Git output")
+			fmt.Println()
+			fmt.Println("PLEASE REPORT THE OUTPUT BELOW AT https://github.com/git-town/git-town/issues/new")
+			fmt.Println()
+			fmt.Printf("Problematic line: %q\n", line)
+			fmt.Println()
+			fmt.Println("BEGIN OUTPUT FROM 'git branch -vva'")
+			fmt.Println(output)
+			fmt.Println("END OUTPUT FROM 'git branch -vva'")
+			os.Exit(1)
+		}
 		branchName := parts[0]
 		var sha domain.SHA
 		if parts[1] == "branch," {