completion: add proper public __git_complete

When __git_complete was introduced, it was meant to be temporarily, while
a proper guideline for public shell functions was established
(tentatively _GIT_complete), but since that never happened, people
in the wild started to use __git_complete, even though it was marked as
not public.

Eight years is more than enough wait, let's mark this function as
public, and make it a bit more user-friendly.

So that instead of doing:

  __git_complete gk __gitk_main

The user can do:

  __git_complete gk gitk

And instead of:

  __git_complete gf _git_fetch

Do:

  __git_complete gf git_fetch

Backwards compatibility is maintained.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -29,6 +29,15 @@
 # tell the completion to use commit completion.  This also works with aliases
 # of form "!sh -c '...'".  For example, "!sh -c ': git commit ; ... '".
 #
+# If you have a command that is not part of git, but you would still
+# like completion, you can use __git_complete:
+#
+#   __git_complete gl git_log
+#
+# Or if it's a main command (i.e. git or gitk):
+#
+#   __git_complete gk gitk
+#
 # Compatible with bash 3.2.57.
 #
 # You can set the following environment variables to influence the behavior of
@@ -3497,10 +3506,7 @@ __git_func_wrap ()
 	$1
 }
 
-# Setup completion for certain functions defined above by setting common
+___git_complete ()
-# variables and workarounds.
-# This is NOT a public function; use at your own risk.
-__git_complete ()
 {
 	local wrapper="__git_wrap${2}"
 	eval "$wrapper () { __git_func_wrap $2 ; }"
@@ -3508,13 +3514,33 @@ __git_complete ()
 		|| complete -o default -o nospace -F $wrapper $1
 }
 
-__git_complete git __git_main
+# Setup the completion for git commands
-__git_complete gitk __gitk_main
+# 1: command or alias
+# 2: function to call (e.g. `git`, `gitk`, `git_fetch`)
+__git_complete ()
+{
+	local func
+
+	if __git_have_func $2; then
+		func=$2
+	elif __git_have_func __$2_main; then
+		func=__$2_main
+	elif __git_have_func _$2; then
+		func=_$2
+	else
+		echo "ERROR: could not find function '$2'" 1>&2
+		return 1
+	fi
+	___git_complete $1 $func
+}
+
+___git_complete git __git_main
+___git_complete gitk __gitk_main
 
 # 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 [ "$OSTYPE" = cygwin ]; then
-	__git_complete git.exe __git_main
+	___git_complete git.exe __git_main
 fi

t/t9902-completion.sh

@@ -2382,10 +2382,22 @@ test_expect_success 'sourcing the completion script clears cached --options' '
 
 test_expect_success '__git_complete' '
 	unset -f __git_wrap__git_main &&
+
 	__git_complete foo __git_main &&
 	__git_have_func __git_wrap__git_main &&
+	unset -f __git_wrap__git_main &&
+
 	__git_complete gf _git_fetch &&
-	__git_have_func __git_wrap_git_fetch
+	__git_have_func __git_wrap_git_fetch &&
+
+	__git_complete foo git &&
+	__git_have_func __git_wrap__git_main &&
+	unset -f __git_wrap__git_main &&
+
+	__git_complete gd git_diff &&
+	__git_have_func __git_wrap_git_diff &&
+
+	test_must_fail __git_complete ga missing
 '
 
 test_done