completion(switch/checkout): treat --track and -t the same

When `git switch --track ` is to be completed, only remote refs are
eligible because that is what the `--track` option targets.

And when the short-hand `-t` is used instead, the same _should_ happen.
Let's make it so.

Note that the bug exists both in the completions of `switch` and
`completion`, even if it manifests in slightly different ways: While
the completion of `git switch -t ` will not even look at remote refs,
the completion of `git checkout -t ` will look at both remote _and_
local refs. Both should look only at remote refs.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -1607,7 +1607,7 @@ _git_checkout ()
 
 		if [ -n "$(__git_find_on_cmdline "-b -B -d --detach --orphan")" ]; then
 			__git_complete_refs --mode="refs"
-		elif [ -n "$(__git_find_on_cmdline "--track")" ]; then
+		elif [ -n "$(__git_find_on_cmdline "-t --track")" ]; then
 			__git_complete_refs --mode="remote-heads"
 		else
 			__git_complete_refs $dwim_opt --mode="refs"
@@ -2484,7 +2484,7 @@ _git_switch ()
 
 		if [ -n "$(__git_find_on_cmdline "-c -C -d --detach")" ]; then
 			__git_complete_refs --mode="refs"
-		elif [ -n "$(__git_find_on_cmdline "--track")" ]; then
+		elif [ -n "$(__git_find_on_cmdline "-t --track")" ]; then
 			__git_complete_refs --mode="remote-heads"
 		else
 			__git_complete_refs $dwim_opt --mode="heads"

t/t9902-completion.sh

@@ -1622,14 +1622,22 @@ test_expect_success 'git checkout - with -d, complete only references' '
 '
 
 test_expect_success 'git switch - with --track, complete only remote branches' '
-	test_completion "git switch --track " <<-\EOF
+	test_completion "git switch --track " <<-\EOF &&
+	other/branch-in-other Z
+	other/main-in-other Z
+	EOF
+	test_completion "git switch -t " <<-\EOF
 	other/branch-in-other Z
 	other/main-in-other Z
 	EOF
 '
 
 test_expect_success 'git checkout - with --track, complete only remote branches' '
-	test_completion "git checkout --track " <<-\EOF
+	test_completion "git checkout --track " <<-\EOF &&
+	other/branch-in-other Z
+	other/main-in-other Z
+	EOF
+	test_completion "git checkout -t " <<-\EOF
 	other/branch-in-other Z
 	other/main-in-other Z
 	EOF