rebase -i --root: let the sequencer handle even the initial part

In this developer's earlier attempt to accelerate interactive rebases by
converting large parts from Unix shell script into portable, performant
C, the --root handling was specifically excluded (to simplify the task a
little bit; it still took over a year to get that reduced set of patches
into Git proper).

This patch ties up that loose end: now only --preserve-merges uses the
slow Unix shell script implementation to perform the interactive rebase.

As the rebase--helper reports progress to stderr (unlike the scripted
interactive rebase, which reports it to stdout, of all places), we have
to adjust a couple of tests that did not expect that for `git rebase -i
--root`.

This patch fixes -- at long last! -- the really old bug reported in
6a6bc5bdc4d (add tests for rebasing root, 2013-06-06) that rebasing with
--root *always* rewrote the root commit, even if there were no changes.

The bug still persists in --preserve-merges mode, of course, but that
mode will be deprecated as soon as the new --rebase-merges mode
stabilizes, anyway.

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

1 files changed, 3 insertions, 1 deletions

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index cbf44f8648..2f4941d0fc 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -894,6 +894,8 @@ init_revisions_and_shortrevisions () {
 	else
 		revisions=$onto...$orig_head
 		shortrevisions=$shorthead
+		test -z "$squash_onto" ||
+		echo "$squash_onto" >"$state_dir"/squash-onto
 	fi
 }
 
@@ -948,7 +950,7 @@ EOF
 	die "Could not skip unnecessary pick commands"
 
 	checkout_onto
-	if test -z "$rebase_root" && test ! -d "$rewritten"
+	if test ! -d "$rewritten"
 	then
 		require_clean_work_tree "rebase"
 		exec git rebase--helper ${force_rebase:+--no-ff} $allow_empty_message \