rebase--interactive: fix parent rewriting for dropped commits

`rebase -i -p` got its rev-list of commits to keep by --left-right and
--cherry-pick. Adding --cherry-pick would drop commits that duplicated changes
already in the rebase target.

The dropped commits were then forgotten about when it came to rewriting the
parents of their descendents, so the descendents would get cherry-picked with
their old, unwritten parents and essentially make the rebase a no-op.

This commit adds a $DOTEST/dropped directory to remember dropped commits and
rewrite their children's parent as the dropped commit's possibly-rewritten
first-parent.

Signed-off-by: Stephen Haberman <stephen@exigencecorp.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 35 insertions, 2 deletions

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 124cb5846..30e45237a 100755
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -37,6 +37,7 @@ DONE="$DOTEST"/done
 MSG="$DOTEST"/message
 SQUASH_MSG="$DOTEST"/message-squash
 REWRITTEN="$DOTEST"/rewritten
+DROPPED="$DOTEST"/dropped
 PRESERVE_MERGES=
 STRATEGY=
 ONTO=
@@ -179,8 +180,12 @@ pick_one_preserving_merges () {
 
 	# rewrite parents; if none were rewritten, we can fast-forward.
 	new_parents=
-	for p in $(git rev-list --parents -1 $sha1 | cut -d' ' -f2-)
+	pend=" $(git rev-list --parents -1 $sha1 | cut -d' ' -f2-)"
+	while [ "$pend" != "" ]
 	do
+		p=$(expr "$pend" : ' \([^ ]*\)')
+		pend="${pend# $p}"
+
 		if test -f "$REWRITTEN"/$p
 		then
 			new_p=$(cat "$REWRITTEN"/$p)
@@ -193,7 +198,13 @@ pick_one_preserving_merges () {
 				;;
 			esac
 		else
-			new_parents="$new_parents $p"
+			if test -f "$DROPPED"/$p
+			then
+				fast_forward=f
+				pend=" $(cat "$DROPPED"/$p)$pend"
+			else
+				new_parents="$new_parents $p"
+			fi
 		fi
 	done
 	case $fast_forward in
@@ -599,6 +610,28 @@ first and then run 'git rebase --continue' again."
 #
 EOF
 
+		# Watch for commits that been dropped by --cherry-pick
+		if test t = "$PRESERVE_MERGES"
+		then
+			mkdir "$DROPPED"
+			# drop the --cherry-pick parameter this time
+			git rev-list $MERGES_OPTION --abbrev-commit \
+				--abbrev=7 $UPSTREAM...$HEAD --left-right | \
+				sed -n "s/^>//p" | while read rev
+			do
+				grep --quiet "$rev" "$TODO"
+				if [ $? -ne 0 ]
+				then
+					# Use -f2 because if rev-list is telling this commit is not
+					# worthwhile, we don't want to track its multiple heads,
+					# just the history of its first-parent for others that will
+					# be rebasing on top of us
+					full=$(git rev-parse $rev)
+					git rev-list --parents -1 $rev | cut -d' ' -f2 > "$DROPPED"/$full
+				fi
+			done
+		fi
+
 		has_action "$TODO" ||
 			die_abort "Nothing to do"