checkout: call a single commit "it" intead of "them"
checkout: call a single commit "it" intead of "them"

When detached and checking out a branch again, git checkout warns
about commit(s) that might get lost.  It says "If you want to keep
them ..." even for only one commit.

Use Q_() to allow differentiating singular vs plural.

Signed-off-by: Thomas Schneider <6db98389b30108e0095ac10136b50ad76e34ea91@gmail.com>
Reviewed-by: Jonathan Nieder <b57189c5f2fd5b3daf3350a77fde90def1080fa5@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git