Merge branch 'bc/completion-for-bash-3.0' into maint

Some people still use rather old versions of bash, which cannot grok
some constructs like 'printf -v varname' the prompt and completion
code started to use recently.

* bc/completion-for-bash-3.0:
  contrib/git-prompt.sh: handle missing 'printf -v' more gracefully
  t9902-completion.sh: old Bash still does not support array+=('') notation
  git-completion.bash: use correct Bash/Zsh array length syntax

contrib/completion/git-completion.bash

@@ -2580,7 +2580,7 @@ if [[ -n ${ZSH_VERSION-} ]]; then
 				--*=*|*.) ;;
 				*) c="$c " ;;
 				esac
-				array[$#array+1]="$c"
+				array[${#array[@]}+1]="$c"
 			done
 			compset -P '*[=:]'
 			compadd -Q -S '' -p "${2-}" -a -- array && _ret=0

contrib/completion/git-prompt.sh

@@ -84,6 +84,10 @@
 # the colored output of "git status -sb" and are available only when
 # using __git_ps1 for PROMPT_COMMAND or precmd.
 
+# check whether printf supports -v
+__git_printf_supports_v=
+printf -v __git_printf_supports_v -- '%s' yes >/dev/null 2>&1
+
 # stores the divergence from upstream in $p
 # used by GIT_PS1_SHOWUPSTREAM
 __git_ps1_show_upstream ()
@@ -433,7 +437,7 @@ __git_ps1 ()
 	local gitstring="$c${b##refs/heads/}${f:+$z$f}$r$p"
 
 	if [ $pcmode = yes ]; then
-		if [[ -n ${ZSH_VERSION-} ]]; then
+		if [ "${__git_printf_supports_v-}" != yes ]; then
 			gitstring=$(printf -- "$printf_format" "$gitstring")
 		else
 			printf -v gitstring -- "$printf_format" "$gitstring"

t/t9902-completion.sh

@@ -69,7 +69,7 @@ run_completion ()
 	local -a COMPREPLY _words
 	local _cword
 	_words=( $1 )
-	test "${1: -1}" = ' ' && _words+=('')
+	test "${1: -1}" = ' ' && _words[${#_words[@]}+1]=''
 	(( _cword = ${#_words[@]} - 1 ))
 	__git_wrap__git_main && print_comp
 }