Backport [v2]: Fix some issues in bash autocompletion

autocomplete/bash_autocomplete

@@ -2,17 +2,31 @@
 
 : ${PROG:=$(basename ${BASH_SOURCE})}
 
+# Macs have bash3 for which the bash-completion package doesn't include
+# _init_completion. This is a minimal version of that function.
+_cli_init_completion() {
+  COMPREPLY=()
+  _get_comp_words_by_ref "$@" cur prev words cword
+}
+
 _cli_bash_autocomplete() {
   if [[ "${COMP_WORDS[0]}" != "source" ]]; then
-    local cur opts base
+    local cur opts base words
     COMPREPLY=()
     cur="${COMP_WORDS[COMP_CWORD]}"
+    if declare -F _init_completion >/dev/null 2>&1; then
+      _init_completion -n "=:" || return
+    else
+      _cli_init_completion -n "=:" || return
+    fi
+    words=("${words[@]:0:$cword}")
     if [[ "$cur" == "-"* ]]; then
-      opts=$( ${COMP_WORDS[@]:0:$COMP_CWORD} ${cur} --generate-bash-completion )
+      requestComp="${words[*]} ${cur} --generate-bash-completion"
     else
-      opts=$( ${COMP_WORDS[@]:0:$COMP_CWORD} --generate-bash-completion )
+      requestComp="${words[*]} --generate-bash-completion"
     fi
-    COMPREPLY=( $(compgen -W "${opts}" -- ${cur}) )
+    opts=$(eval "${requestComp}" 2>/dev/null)
+    COMPREPLY=($(compgen -W "${opts}" -- ${cur}))
     return 0
   fi
 }

help_test.go

@@ -1195,6 +1195,28 @@ func TestDefaultCompleteWithFlags(t *testing.T) {
 			argv:     []string{"cmd", "--generate-bash-completion"},
 			expected: "futz\n",
 		},
+		{
+			name: "autocomplete-with-spaces",
+			c: &Context{App: &App{
+				Name: "cmd",
+				Flags: []Flag{
+					&BoolFlag{Name: "happiness"},
+					&Int64Flag{Name: "everybody-jump-on"},
+				},
+			}},
+			cmd: &Command{
+				Name: "putz",
+				Subcommands: []*Command{
+					{Name: "help"},
+				},
+				Flags: []Flag{
+					&BoolFlag{Name: "excitement"},
+					&StringFlag{Name: "hat-shape"},
+				},
+			},
+			argv:     []string{"cmd", "--url", "http://localhost:8000", "h", "--generate-bash-completion"},
+			expected: "help\n",
+		},
 	} {
 		t.Run(tc.name, func(ct *testing.T) {
 			writer := &bytes.Buffer{}