bash completion: refactor --strategy completion
bash completion: refactor --strategy completion

The code to complete --strategy was duplicated between _git_rebase and
_git_merge, and is about to gain a third caller (_git_pull). This patch
factors it into its own function.

Signed-off-by: Jay Soffian <eccf10a4397cf08f0034a6cb5e4457bdd5e3783e@gmail.com>
Acked-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>
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