Teach bash how to complete git-rebase.

As git-rebase is a popular command bash should know how to complete
reference names and its long options.  We only support completions
which make sense given the current state of the repository, that
way users don't get shown --continue/--skip/--abort on the first
execution.

Also added support for long option --strategy to git-merge, as I
missed that option earlier and just noticed it while implementing
git-rebase.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

contrib/completion/git-completion.bash

@@ -367,16 +367,16 @@ _git_merge ()
 	case "$cur" in
 	--*)
 		COMPREPLY=($(compgen -W "
-			--no-commit --no-summary --squash
+			--no-commit --no-summary --squash --strategy
 			" -- "$cur"))
 		return
 	esac
-	if [ $COMP_CWORD -gt 1 -a X-s = "X${COMP_WORDS[COMP_CWORD-1]}" ]
-	then
+	case "${COMP_WORDS[COMP_CWORD-1]}" in
+	-s|--strategy)
 		COMPREPLY=($(compgen -W "$(__git_merge_strategies)" -- "$cur"))
-	else
-		COMPREPLY=($(compgen -W "$(__git_refs)" -- "$cur"))
-	fi
+		return
+	esac
+	COMPREPLY=($(compgen -W "$(__git_refs)" -- "$cur"))
 }
 
 _git_merge_base ()
@@ -443,6 +443,30 @@ _git_push ()
 	esac
 }
 
+_git_rebase ()
+{
+	local cur="${COMP_WORDS[COMP_CWORD]}"
+	if [ -d .dotest ]; then
+		COMPREPLY=($(compgen -W "
+			--continue --skip --abort
+			" -- "$cur"))
+		return
+	fi
+	case "$cur" in
+	--*)
+		COMPREPLY=($(compgen -W "
+			--onto --merge --strategy
+			" -- "$cur"))
+		return
+	esac
+	case "${COMP_WORDS[COMP_CWORD-1]}" in
+	-s|--strategy)
+		COMPREPLY=($(compgen -W "$(__git_merge_strategies)" -- "$cur"))
+		return
+	esac
+	COMPREPLY=($(compgen -W "$(__git_refs)" -- "$cur"))
+}
+
 _git_reset ()
 {
 	local cur="${COMP_WORDS[COMP_CWORD]}"
@@ -500,6 +524,7 @@ _git ()
 	name-rev)    _git_name_rev ;;
 	pull)        _git_pull ;;
 	push)        _git_push ;;
+	rebase)      _git_rebase ;;
 	reset)       _git_reset ;;
 	show)        _git_show ;;
 	show-branch) _git_log ;;
@@ -532,6 +557,7 @@ complete -o default            -F _git_merge_base git-merge-base
 complete -o default            -F _git_name_rev git-name-rev
 complete -o default -o nospace -F _git_pull git-pull
 complete -o default -o nospace -F _git_push git-push
+complete -o default            -F _git_rebase git-rebase
 complete -o default            -F _git_reset git-reset
 complete -o default            -F _git_show git-show
 complete -o default -o nospace -F _git_log git-show-branch