diff --git a/Library/Contributions/brew_bash_completion.sh b/Library/Contributions/brew_bash_completion.sh
index 52e0089104..de0228bd0e 100644
--- a/Library/Contributions/brew_bash_completion.sh
+++ b/Library/Contributions/brew_bash_completion.sh
@@ -1,236 +1,335 @@
 # Bash completion script for brew(1)
 #
-# To use, edit your .bashrc and add:
-#   source `brew --prefix`/Library/Contributions/brew_bash_completion.sh
+# To use, add the following to your .bashrc:
+#
+#    . $(brew --repository)/Library/Contributions/brew_bash_completion.sh
+#
+# Alternatively, if you have installed the bash-completion package,
+# you can create a symlink to this file in one of the following directories:
+#
+#    $(brew --prefix)/etc/bash_completion.d
+#    $(brew --prefix)/share/bash-completion/completions
+#
+# and bash-completion will source it automatically.
 #
 # The __brew_ps1() function can be used to annotate your PS1 with
 # Homebrew debugging information; it behaves similarly to the __git_ps1()
 # function provided by the git's bash completion script.
 #
 # For example, the prompt string
+#
 #     PS1='\u@\h \W $(__brew_ps1 "(%s)") $'
 #
 # would result in a prompt like
+#
 #    user@hostname cwd $
 #
 # but if you are currently engaged in an interactive or debug install,
 # (i.e., you invoked `brew install` with either '-i' or '-d'), then the
 # prompt would look like
-#     user@hostname cwd (formula_name|DEBUG) $
+#
+#     user@hostname cwd (<formula_name>|DEBUG) $
 #
 # You can customize the output string, e.g. $(__brew_ps1 "[%s]") would
-# output "[formula_name|DEBUG]". The default (if you do not provide a
-# format argument) is to print "(formula_name|DEBUG)" prefixed with a
+# output "[<formula_name>|DEBUG]". The default (if you do not provide a
+# format argument) is to print "(<formula_name>|DEBUG)" prefixed with a
 # single space.
 
-_brew_to_completion()
+__brewcomp_words_include ()
 {
-    local cur="${COMP_WORDS[COMP_CWORD]}"
+	local i=1
+	while [[ $i -lt $COMP_CWORD ]]; do
+		if [[ "${COMP_WORDS[i]}" = "$1" ]]; then
+			return 0
+		fi
+		i=$((++i))
+	done
+	return 1
+}
 
-    # Subcommand list
-    [[ ${COMP_CWORD} -eq 1 ]] && {
-        local actions="--cache --cellar --config --env --prefix --repository audit cat cleanup
-            configure create deps diy doctor edit fetch help home info install link list log options
-            outdated prune remove search test uninstall unlink update upgrade uses versions"
-        local ext=$(\ls $(brew --repository)/Library/Contributions/examples 2> /dev/null |
-                    sed -e "s/\.rb//g" -e "s/brew-//g")
-        COMPREPLY=( $(compgen -W "${actions} ${ext}" -- ${cur}) )
-        return
-    }
+# Find the previous non-switch word
+__brewcomp_prev ()
+{
+	local idx=$((COMP_CWORD - 1))
+	local prv="${COMP_WORDS[idx]}"
+	while [[ $prv == -* ]]; do
+		idx=$((--idx))
+		prv="${COMP_WORDS[idx]}"
+	done
+	echo "$prv"
+}
 
-    # some flags take arguments
-    # kind of pointless to use a case statement here, but it's cleaner
-    # than a bunch of string comparisons and leaves room for future
-    # expansion
-    case "${COMP_WORDS[1]}" in
-    # flags that take a formula
-    --cache|--cellar|--prefix)
-        local ff=$(\ls $(brew --repository)/Library/Formula 2> /dev/null | sed "s/\.rb//g")
-        local af=$(\ls $(brew --repository)/Library/Aliases 2> /dev/null | sed "s/\.rb//g")
-        COMPREPLY=( $(compgen -W "${ff} ${af}" -- ${cur}) )
-        return
-        ;;
-    esac
+__brewcomp ()
+{
+	# break $1 on space, tab, and newline characters,
+	# and turn it into a newline separated list of words
+	local list s sep=$'\n' IFS=$' '$'\t'$'\n'
+	local cur="${COMP_WORDS[COMP_CWORD]}"
 
-    # Find the previous non-switch word
-    local prev_index=$((COMP_CWORD - 1))
-    local prev="${COMP_WORDS[prev_index]}"
-    while [[ $prev == -* ]]; do
-        prev_index=$((--prev_index))
-        prev="${COMP_WORDS[prev_index]}"
-    done
+	for s in $1; do
+		__brewcomp_words_include "$s" && continue
+		list="$list$s$sep"
+	done
 
-    # handle subcommand options
-    if [[  "$cur" == --* ]]; then
-        case "${COMP_WORDS[1]}" in
-        cleanup)
-            local opts=$([[ "${COMP_WORDS[*]}" =~ "--force" ]] || echo "--force")
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        create)
-            local opts=$(
-                local opts=(--autotools --cmake --no-fetch)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        deps)
-            local opts=$(
-                local opts=(--1 --all --tree)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        diy|configure)
-            local opts=$(
-                local opts=(--set-version --set-name)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        fetch)
-            local opts=$(
-                local opts=(--deps --force --HEAD)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        info|abv)
-            local opts=$(
-                local opts=(--all --github)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        install)
-            local opts=$(
-                local opts=(--force --verbose --debug --use-clang --use-gcc
-                    --use-llvm --ignore-dependencies --build-from-source --HEAD
-                    --interactive --fresh --devel $(brew options --compact "$prev"))
+	IFS=$sep
+	COMPREPLY=($(compgen -W "$list" -- "$cur"))
+}
 
-                # options that make sense with '--interactive'
-                if [[ "${COMP_WORDS[*]}" =~ "--interactive" ]]; then
-                    opts=(--force --git --use-clang --use-gcc --use-llvm --HEAD --devel)
-                fi
+# Don't use __brewcomp() in any of the __brew_complete_foo functions, as
+# it is too slow and is not worth it just for duplicate elimination.
+__brew_complete_formulae ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	local ff=$(\ls $(brew --repository)/Library/Formula 2>/dev/null | sed 's/\.rb//g')
+        local af=$(\ls $(brew --repository)/Library/Aliases 2>/dev/null | sed 's/\.rb//g')
+        COMPREPLY=($(compgen -W "$ff $af" -- "$cur"))
+}
 
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        list|ls)
-            local opts=$(
-                local opts=(--unbrewed --verbose --versions)
+__brew_complete_installed ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	local inst=$(\ls $(brew --cellar))
+	COMPREPLY=($(compgen -W "$inst" -- "$cur"))
+}
 
-                # the three options for list are mutually exclusive
-                for o in ${opts[*]}; do
-                    if [[ "${COMP_WORDS[*]}" =~ "$o" ]]; then
-                        opts=()
-                    else
-                        echo "$o"
-                    fi
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        options)
-            local opts=$(
-                local opts=(--all --compact --installed)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        outdated)
-            local opts=$([[ "${COMP_WORDS[*]}" =~ "--quiet" ]] || echo "--quiet")
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        search|-S)
-            local opts=$(
-                local opts=(--fink --macports)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        uninstall|remove|rm)
-            local opts=$([[ "${COMP_WORDS[*]}" =~ "--force" ]] || echo "--force")
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        update)
-            local opts=$(
-                local opts=(--rebase --verbose)
-                for o in ${opts[*]}; do
-                    [[ "${COMP_WORDS[*]}" =~ "$o" ]] || echo "$o"
-                done
-            )
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        uses)
-            local opts=$([[ "${COMP_WORDS[*]}" =~ "--installed" ]] || echo "--installed")
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        versions)
-            local opts=$([[ "${COMP_WORDS[*]}" =~ "--compact" ]] || echo "--compact")
-            COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
-            return
-            ;;
-        esac
-    fi
+__brew_complete_outdated ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	local od=$(brew outdated --quiet)
+	COMPREPLY=($(compgen -W "$od" -- "$cur"))
+}
 
-    # find the index of the *first* non-switch word
-    # we can use this to allow completion for multiple formula arguments
-    local cmd_index=1
-    while [[ ${COMP_WORDS[cmd_index]} == -* ]]; do
-        cmd_index=$((++cmd_index))
-    done
+_brew_cleanup ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--force"
+		return
+		;;
+	esac
+	__brew_complete_installed
+}
 
-    case "${COMP_WORDS[cmd_index]}" in
-    # Commands that take a formula
-    audit|cat|deps|edit|fetch|home|homepage|info|install|log|missing|options|uses|versions)
-        local ff=$(\ls $(brew --repository)/Library/Formula 2> /dev/null | sed "s/\.rb//g")
-        local af=$(\ls $(brew --repository)/Library/Aliases 2> /dev/null | sed "s/\.rb//g")
-        COMPREPLY=( $(compgen -W "${ff} ${af}" -- ${cur}) )
-        return
-        ;;
-    # Commands that take an existing brew
-    abv|cleanup|link|list|ln|ls|remove|rm|test|uninstall|unlink)
-        COMPREPLY=( $(compgen -W "$(\ls $(brew --cellar))" -- ${cur}) )
-        return
-        ;;
-    # Commands that take an outdated brew
-    upgrade)
-        COMPREPLY=( $(compgen -W "$(brew outdated --quiet)" -- ${cur}) )
-        return
-        ;;
-    esac
+_brew_create ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--autotools --cmake --no-fetch"
+		return
+		;;
+	esac
+}
+
+_brew_deps ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--1 --all --tree"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_diy ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--set-name --set-version"
+		return
+		;;
+	esac
+}
+
+_brew_fetch ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--deps --force --HEAD"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_info ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--all --github"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_install ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	local prv=$(__brewcomp_prev)
+
+	case "$cur" in
+	--*)
+		if __brewcomp_words_include "--interactive"; then
+			__brewcomp "
+				--devel
+				--force
+				--git
+				--HEAD
+				--use-clang
+				--use-gcc
+				--use-llvm
+				"
+		else
+			__brewcomp "
+				--build-from-source
+				--debug
+				--devel
+				--force
+				--fresh
+				--HEAD
+				--ignore-dependencies
+				--interactive
+				--use-clang
+				--use-gcc
+				--use-llvm
+				--verbose
+				$(brew options --compact "$prv")
+				"
+		fi
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_list ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		# options to brew-list are mutually exclusive
+		if __brewcomp_words_include "--unbrewed"; then
+			return
+		elif __brewcomp_words_include "--verbose"; then
+			return
+		elif __brewcomp_words_include "--versions"; then
+			return
+		else
+			__brewcomp "--unbrewed --verbose --versions"
+			return
+		fi
+		;;
+	esac
+	__brew_complete_installed
+}
+
+_brew_log ()
+{
+	# if git-completion is loaded, then we complete git-log options
+	declare -F _git_log >/dev/null || return
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "
+			$__git_log_common_options
+			$__git_log_shortlog_options
+			$__git_log_gitk_options
+			$__git_diff_common_options
+			--walk-reflogs --graph --decorate
+			--abbrev-commit --oneline --reverse
+			"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_options ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--all --compact --installed"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_outdated ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--quiet"
+		return
+		;;
+	esac
+}
+
+_brew_search ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--fink --macports"
+		return
+		;;
+	esac
+}
+
+_brew_uninstall ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--force"
+		return
+		;;
+	esac
+	__brew_complete_installed
+}
+
+_brew_update ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--rebase --verbose"
+		return
+		;;
+	esac
+}
+
+_brew_uses ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--installed"
+		return
+		;;
+	esac
+	__brew_complete_formulae
+}
+
+_brew_versions ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	case "$cur" in
+	--*)
+		__brewcomp "--compact"
+		return
+		;;
+	esac
+	__brew_complete_formulae
 }
 
 __brew_ps1 ()
@@ -239,4 +338,94 @@ __brew_ps1 ()
     printf "${1:- (%s)}" "$HOMEBREW_DEBUG_INSTALL|DEBUG"
 }
 
-complete -o bashdefault -o default -F _brew_to_completion brew
+_brew ()
+{
+	local i=1 cmd
+
+	# find the subcommand
+	while [[ $i -lt $COMP_CWORD ]]; do
+		local s="${COMP_WORDS[i]}"
+		case "$s" in
+		--*) 	cmd="$s"
+			break
+			;;
+		-*)	;;
+		*) 	cmd="$s"
+			break
+			;;
+		esac
+		i=$((++i))
+	done
+
+	if [[ $i -eq $COMP_CWORD ]]; then
+		local ext=$(\ls $(brew --repository)/Library/Contributions/examples \
+			    2>/dev/null | sed -e "s/\.rb//g" -e "s/brew-//g")
+		__brewcomp "
+			--cache --cellar --config
+			--env --prefix --repository
+			audit
+			cat
+			cleanup
+			create
+			deps
+			diy configure
+			doctor
+			edit
+			fetch
+			help
+			home
+			info abv
+			install
+			link ln
+			list ls
+			log
+			options
+			outdated
+			prune
+			search
+			test
+			uninstall remove rm
+			unlink
+			update
+			upgrade
+			uses
+			versions
+			$ext
+			"
+		return
+	fi
+
+	# subcommands have their own completion functions
+	case "$cmd" in
+	--cache|--cellar|--prefix)
+				__brew_complete_formulae ;;
+	audit|cat|edit|home)	__brew_complete_formulae ;;
+	link|ln|test|unlink)	__brew_complete_installed ;;
+	upgrade)		__brew_complete_outdated ;;
+	cleanup)		_brew_cleanup ;;
+	create)			_brew_create ;;
+	deps)			_brew_deps ;;
+	diy|configure)		_brew_diy ;;
+	fetch)			_brew_fetch ;;
+	info|abv)		_brew_info ;;
+	install)		_brew_install ;;
+	list|ls)		_brew_list ;;
+	log)			_brew_log ;;
+	options)		_brew_options ;;
+	outdated)		_brew_outdated ;;
+	search|-S)		_brew_search ;;
+	uninstall|remove|rm) 	_brew_uninstall ;;
+	update)			_brew_update ;;
+	uses)			_brew_uses ;;
+	versions)		_brew_versions ;;
+	*)			;;
+	esac
+}
+
+# keep around for compatibility
+_brew_to_completion ()
+{
+	_brew
+}
+
+complete -o bashdefault -o default -F _brew brew