completion: introduce __gitcomp_nl_append ()

There are situations where multiple classes of completions possible. For
example

  branch.<TAB>

should try to complete

  branch.master.
  branch.autosetupmerge
  branch.autosetuprebase

The first candidate has the suffix ".", and the second/ third candidates
have the suffix " ". To facilitate completions of this kind, create a
variation of __gitcomp_nl () that appends to the existing list of
completion candidates, COMPREPLY.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.zsh

@@ -76,6 +76,14 @@ __gitcomp_nl ()
 	compadd -Q -S "${4- }" -p "${2-}" -- ${=1} && _ret=0
 }
 
+__gitcomp_nl_append ()
+{
+	emulate -L zsh
+
+	local IFS=$'\n'
+	compadd -Q -S "${4- }" -p "${2-}" -- ${=1} && _ret=0
+}
+
 __gitcomp_file ()
 {
 	emulate -L zsh