v6, 3 partscompletion: refactor and zsh wrapper

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index be800e0..7bdd6a8 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -238,7 +238,6 @@ __gitcomp ()
 
 	case "$cur_" in
 	--*=)
-		COMPREPLY=()
 		;;
 	*)
 		local IFS=$'\n'
@@ -486,7 +485,6 @@ __git_complete_remote_or_refspec ()
 			case "$cmd" in
 			push) no_complete_refspec=1 ;;
 			fetch)
-				COMPREPLY=()
 				return
 				;;
 			*) ;;
@@ -502,7 +500,6 @@ __git_complete_remote_or_refspec ()
 		return
 	fi
 	if [ $no_complete_refspec = 1 ]; then
-		COMPREPLY=()
 		return
 	fi
 	[ "$remote" = "." ] && remote=
@@ -776,7 +773,6 @@ _git_am ()
 			"
 		return
 	esac
-	COMPREPLY=()
 }
 
 _git_apply ()
@@ -796,7 +792,6 @@ _git_apply ()
 			"
 		return
 	esac
-	COMPREPLY=()
 }
 
 _git_add ()
@@ -811,7 +806,6 @@ _git_add ()
 			"
 		return
 	esac
-	COMPREPLY=()
 }
 
 _git_archive ()
@@ -856,7 +850,6 @@ _git_bisect ()
 		__gitcomp_nl "$(__git_refs)"
 		;;
 	*)
-		COMPREPLY=()
 		;;
 	esac
 }
@@ -969,7 +962,6 @@ _git_clean ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_clone ()
@@ -993,7 +985,6 @@ _git_clone ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_commit ()
@@ -1027,7 +1018,6 @@ _git_commit ()
 			"
 		return
 	esac
-	COMPREPLY=()
 }
 
 _git_describe ()
@@ -1158,7 +1148,6 @@ _git_fsck ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_gc ()
@@ -1169,7 +1158,6 @@ _git_gc ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_gitk ()
@@ -1246,7 +1234,6 @@ _git_init ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_ls_files ()
@@ -1265,7 +1252,6 @@ _git_ls_files ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_ls_remote ()
@@ -1381,7 +1367,6 @@ _git_mergetool ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_merge_base ()
@@ -1397,7 +1382,6 @@ _git_mv ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_name_rev ()
@@ -1567,7 +1551,6 @@ _git_send_email ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_stage ()
@@ -1680,7 +1663,6 @@ _git_config ()
 		return
 		;;
 	*.*)
-		COMPREPLY=()
 		return
 		;;
 	esac
@@ -2060,7 +2042,6 @@ _git_remote ()
 		__gitcomp "$c"
 		;;
 	*)
-		COMPREPLY=()
 		;;
 	esac
 }
@@ -2104,7 +2085,6 @@ _git_rm ()
 		return
 		;;
 	esac
-	COMPREPLY=()
 }
 
 _git_shortlog ()
@@ -2173,8 +2153,6 @@ _git_stash ()
 		*)
 			if [ -z "$(__git_find_on_cmdline "$save_opts")" ]; then
 				__gitcomp "$subcommands"
-			else
-				COMPREPLY=()
 			fi
 			;;
 		esac
@@ -2187,14 +2165,12 @@ _git_stash ()
 			__gitcomp "--index --quiet"
 			;;
 		show,--*|drop,--*|branch,--*)
-			COMPREPLY=()
 			;;
 		show,*|apply,*|drop,*|pop,*|branch,*)
 			__gitcomp_nl "$(git --git-dir="$(__gitdir)" stash list \
 					| sed -n -e 's/:.*//p')"
 			;;
 		*)
-			COMPREPLY=()
 			;;
 		esac
 	fi
@@ -2311,7 +2287,6 @@ _git_svn ()
 			__gitcomp "--revision= --parent"
 			;;
 		*)
-			COMPREPLY=()
 			;;
 		esac
 	fi
@@ -2336,13 +2311,10 @@ _git_tag ()
 
 	case "$prev" in
 	-m|-F)
-		COMPREPLY=()
 		;;
 	-*|tag)
 		if [ $f = 1 ]; then
 			__gitcomp_nl "$(__git_tags)"
-		else
-			COMPREPLY=()
 		fi
 		;;
 	*)

diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
index 7bdd6a8..975ae13 100644
--- a/contrib/completion/git-completion.bash
+++ b/contrib/completion/git-completion.bash
@@ -225,6 +225,11 @@ _get_comp_words_by_ref ()
 fi
 fi
 
+__gitcompadd ()
+{
+	COMPREPLY=($(compgen -W "$1" -P "$2" -S "$4" -- "$3"))
+}
+
 # Generates completion reply with compgen, appending a space to possible
 # completion words, if necessary.
 # It accepts 1 to 4 arguments:
@@ -241,9 +246,7 @@ __gitcomp ()
 		;;
 	*)
 		local IFS=$'\n'
-		COMPREPLY=($(compgen -P "${2-}" \
-			-W "$(__gitcomp_1 "${1-}" "${4-}")" \
-			-- "$cur_"))
+		__gitcompadd "$(__gitcomp_1 "${1-}" "${4-}")" "${2-}" "$cur_" ""
 		;;
 	esac
 }
@@ -260,7 +263,7 @@ __gitcomp ()
 __gitcomp_nl ()
 {
 	local IFS=$'\n'
-	COMPREPLY=($(compgen -P "${2-}" -S "${4- }" -W "$1" -- "${3-$cur}"))
+	__gitcompadd "$1" "${2-}" "${3-$cur}" "${4- }"
 }
 
 __git_heads ()
@@ -1603,7 +1606,7 @@ _git_config ()
 		local remote="${prev#remote.}"
 		remote="${remote%.fetch}"
 		if [ -z "$cur" ]; then
-			COMPREPLY=("refs/heads/")
+			__gitcompadd "refs/heads/"
 			return
 		fi
 		__gitcomp_nl "$(__git_refs_remotes "$remote")"

diff --git a/contrib/completion/git-completion.zsh b/contrib/completion/git-completion.zsh
new file mode 100644
index 0000000..ae9c532
--- /dev/null
+++ b/contrib/completion/git-completion.zsh
@@ -0,0 +1,48 @@
+#compdef git gitk
+
+# zsh completion wrapper for git
+#
+# You need git's bash completion script installed somewhere, by default on the
+# same directory as this script.
+#
+# If your script is on ~/.git-completion.sh instead, you can configure it on
+# your ~/.zshrc:
+#
+#  zstyle ':completion:*:*:git:*' script ~/.git-completion.sh
+#
+# The recommended way to install this script is to copy to
+# '~/.zsh/completion/_git', and then add the following to your ~/.zshrc file:
+#
+#  fpath=(~/.zsh/completion $fpath)
+
+complete ()
+{
+	# do nothing
+	return 0
+}
+
+zstyle -s ":completion:*:*:git:*" script script
+test -z "$script" && script="$(dirname ${funcsourcetrace[1]%:*})"/git-completion.bash
+ZSH_VERSION='' . "$script"
+
+__gitcompadd ()
+{
+	compadd -Q -S "$4" -P "${(M)cur#*[=:]}" -p "$2" -- ${=1} && _ret=0
+}
+
+_git ()
+{
+	local _ret=1
+	() {
+		emulate -L ksh
+		local cur cword prev
+		cur=${words[CURRENT-1]}
+		prev=${words[CURRENT-2]}
+		let cword=CURRENT-1
+		__${service}_main
+	}
+	let _ret && _default -S '' && _ret=0
+	return _ret
+}
+
+_git