rebase: use the new git-rebase--preserve-merges.sh

Create a new type of rebase, "preserve-merges", used when rebase is
called with -p.

Before that, the type for preserve-merges was "interactive", and some
places of this script compared $type to "interactive". Instead, the code
now checks if $interactive_rebase is empty or not, as it is set to
"explicit" when calling an interactive rebase (and, possibly, one of its
submodes), and "implied" when calling one of its
submodes (eg. preserve-merges) *without* interactive rebase.

It also detects the presence of the directory "$merge_dir"/rewritten
left by the preserve-merges script when calling rebase --continue,
--skip, etc., and, if it exists, sets the rebase mode to
preserve-merges. In this case, interactive_rebase is set to "explicit",
as "implied" would break some tests.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>

git-rebase.sh

@@ -207,7 +207,14 @@ run_specific_rebase () {
 		autosquash=
 	fi
 	. git-rebase--$type
-	git_rebase__$type${preserve_merges:+__preserve_merges}
+
+	if test -z "$preserve_merges"
+	then
+		git_rebase__$type
+	else
+		git_rebase__preserve_merges
+	fi
+
 	ret=$?
 	if test $ret -eq 0
 	then
@@ -239,7 +246,12 @@ then
 	state_dir="$apply_dir"
 elif test -d "$merge_dir"
 then
-	if test -f "$merge_dir"/interactive
+	if test -d "$merge_dir"/rewritten
+	then
+		type=preserve-merges
+		interactive_rebase=explicit
+		preserve_merges=t
+	elif test -f "$merge_dir"/interactive
 	then
 		type=interactive
 		interactive_rebase=explicit
@@ -402,14 +414,14 @@ if test -n "$action"
 then
 	test -z "$in_progress" && die "$(gettext "No rebase in progress?")"
 	# Only interactive rebase uses detailed reflog messages
-	if test "$type" = interactive && test "$GIT_REFLOG_ACTION" = rebase
+	if test -n "$interactive_rebase" && test "$GIT_REFLOG_ACTION" = rebase
 	then
 		GIT_REFLOG_ACTION="rebase -i ($action)"
 		export GIT_REFLOG_ACTION
 	fi
 fi
 
-if test "$action" = "edit-todo" && test "$type" != "interactive"
+if test "$action" = "edit-todo" && test -z "$interactive_rebase"
 then
 	die "$(gettext "The --edit-todo action can only be used during interactive rebase.")"
 fi
@@ -487,7 +499,13 @@ fi
 
 if test -n "$interactive_rebase"
 then
-	type=interactive
+	if test -z "$preserve_merges"
+	then
+		type=interactive
+	else
+		type=preserve-merges
+	fi
+
 	state_dir="$merge_dir"
 elif test -n "$do_merge"
 then
@@ -647,7 +665,7 @@ require_clean_work_tree "rebase" "$(gettext "Please commit or stash them.")"
 # but this should be done only when upstream and onto are the same
 # and if this is not an interactive rebase.
 mb=$(git merge-base "$onto" "$orig_head")
-if test "$type" != interactive && test "$upstream" = "$onto" &&
+if test -z "$interactive_rebase" && test "$upstream" = "$onto" &&
 	test "$mb" = "$onto" && test -z "$restrict_revision" &&
 	# linear history?
 	! (git rev-list --parents "$onto".."$orig_head" | sane_grep " .* ") > /dev/null
@@ -691,7 +709,7 @@ then
 	GIT_PAGER='' git diff --stat --summary "$mb" "$onto"
 fi
 
-test "$type" = interactive && run_specific_rebase
+test -n "$interactive_rebase" && run_specific_rebase
 
 # Detach HEAD and reset the tree
 say "$(gettext "First, rewinding head to replay your work on top of it...")"