bash-completion: Try bash completions before simple filetype

When a git completion is not found, a bash shell should try bash-type
completions first before going to standard filetype completions. This
patch adds "-o bashdefault" to the completion line. If that option is
not available, it uses the old method.

This behavior was inspired by Mercurial's bash completion script.

Signed-off-by: Ted Pavlic <[email protected]>
Acked-by: Shawn O. Pearce <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: tpavlic

contrib/completion/git-completion.bash

@@ -1766,13 +1766,16 @@ _gitk ()
 	__git_complete_revlist
 }
 
-complete -o default -o nospace -F _git git
-complete -o default -o nospace -F _gitk gitk
+complete -o bashdefault -o default -o nospace -F _git git 2>/dev/null \
+	|| complete -o default -o nospace -F _git git
+complete -o bashdefault -o default -o nospace -F _gitk gitk 2>/dev/null \
+	|| complete -o default -o nospace -F _gitk gitk
 
 # The following are necessary only for Cygwin, and only are needed
 # when the user has tab-completed the executable name and consequently
 # included the '.exe' suffix.
 #
 if [ Cygwin = "$(uname -o 2>/dev/null)" ]; then
-complete -o default -o nospace -F _git git.exe
+complete -o bashdefault -o default -o nospace -F _git git.exe 2>/dev/null \
+	|| complete -o default -o nospace -F _git git.exe
 fi