fix bash completion of filenames containing spaces

Work around https://github.com/pcapriotti/optparse-applicative/issues/146
by not using action "file" and instead passing -o bashdefault -o default
to complete. This way, when optparse fails to complete a filename, bash
will fall back to regular filename completion.

Unfortunately, optparse-applicative does not provide a way to control the
options passed to complete, so I had to modify its generated completion script.

Note that for "git annex" command completion, git's completion script already
used -o bashdefault -o default, so that works too.

CmdLine/GitAnnex/Options.hs

@@ -89,8 +89,6 @@ gitAnnexGlobalOptions = commonGlobalOptions ++
 cmdParams :: CmdParamsDesc -> Parser CmdParams
 cmdParams paramdesc = many $ argument str
 	( metavar paramdesc
-	-- Let bash completion complete files
-	<> action "file"
 	)
 
 parseAutoOption :: Parser Bool

bash-completion.bash

@@ -1,7 +1,19 @@
 # Use git-annex's built-in bash completion
 # This bash completion is generated by the option parser, so it covers all
 # commands, all options, and will never go out of date!
-source <(git-annex --bash-completion-script git-annex)
+_git-annex()
+{
+    local cmdline
+    CMDLINE=(--bash-completion-index $COMP_CWORD)
+
+    for arg in ${COMP_WORDS[@]}; do
+        CMDLINE=(${CMDLINE[@]} --bash-completion-word $arg)
+    done
+
+    COMPREPLY=( $(git-annex "${CMDLINE[@]}") )
+}
+
+complete -o bashdefault -o default -o filenames -F _git-annex git-annex
 
 # Called by git's bash completion script when completing "git annex"
 _git_annex() {