completion: support switch

Completion support for --guess could be made better. If no --detach is
given, we should only provide a list of refs/heads/* and dwim ones,
not the entire ref space. But I still can't penetrate that
__git_refs() function yet.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -37,7 +37,8 @@
 #   GIT_COMPLETION_CHECKOUT_NO_GUESS
 #
 #     When set to "1", do not include "DWIM" suggestions in git-checkout
-#     completion (e.g., completing "foo" when "origin/foo" exists).
+#     and git-switch completion (e.g., completing "foo" when "origin/foo"
+#     exists).
 
 case "$COMP_WORDBREAKS" in
 *:*) : great ;;
@@ -2158,6 +2159,40 @@ _git_status ()
 	__git_complete_index_file "$complete_opt"
 }
 
+_git_switch ()
+{
+	case "$cur" in
+	--conflict=*)
+		__gitcomp "diff3 merge" "" "${cur##--conflict=}"
+		;;
+	--*)
+		__gitcomp_builtin switch
+		;;
+	*)
+		# check if --track, --no-track, or --no-guess was specified
+		# if so, disable DWIM mode
+		local track_opt="--track" only_local_ref=n
+		if [ "$GIT_COMPLETION_CHECKOUT_NO_GUESS" = "1" ] ||
+		   [ -n "$(__git_find_on_cmdline "--track --no-track --no-guess")" ]; then
+			track_opt=''
+		fi
+		# explicit --guess enables DWIM mode regardless of
+		# $GIT_COMPLETION_CHECKOUT_NO_GUESS
+		if [ -n "$(__git_find_on_cmdline "--guess")" ]; then
+			track_opt='--track'
+		fi
+		if [ -z "$(__git_find_on_cmdline "-d --detach")" ]; then
+			only_local_ref=y
+		fi
+		if [ $only_local_ref = y -a -z "$track_opt" ]; then
+			__gitcomp_direct "$(__git_heads "" "$cur" " ")"
+		else
+			__git_complete_refs $track_opt
+		fi
+		;;
+	esac
+}
+
 __git_config_get_set_variables ()
 {
 	local prevword word config_file= c=$cword