[PATCH] Warnings before rebasing -i published history

[Lucien Kong <Lucien.Kong@ensimag.imag.fr>]

"git rebase -i" can be very dangerous if used on an already published
history. This code detects that one is rewriting a commit that is an
ancestor of a remote-tracking branch, and warns the user through the
editor.

Signed-off-by: Lucien Kong <Lucien.Kong@ensimag.imag.fr>
Signed-off-by: Valentin Duperray <Valentin.Duperray@ensimag.imag.fr>
Signed-off-by: Franck Jonas <Franck.Jonas@ensimag.imag.fr>
Signed-off-by: Thomas Nguy <Thomas.Nguy@ensimag.imag.fr>
Signed-off-by: Huynh Khoi Nguyen Nguyen <Huynh-Khoi-Nguyen.Nguyen@ensimag.imag.fr>
Signed-off-by: Matthieu Moy <Matthieu.Moy@grenoble-inp.fr>
---
For now, the code only warns the user; he can't revert back to his
original state. We agree with everyone that he should be given a
way to abort the rebase.

 git-rebase--interactive.sh    |   17 +++++++++++++++++
 t/t3404-rebase-interactive.sh |   26 ++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 0 deletions(-)

diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 0c19b7c..67b5faf 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -684,6 +684,20 @@ rearrange_squash () {
 	rm -f "$1.sq" "$1.rearranged"
 }
 
+# Add a warning notification at the end of each pick or fixup/squash
+# line of the todo list, providing the picking commit is already
+# published.
+warn_published () {
+	cat "$1" | while read -r command sha1 message
+	do
+		test -n "$sha1" || break
+		if test -n "$(git branch -r --contains "$sha1")"
+		then
+			printf "%s\n" "$(sed -e "/"$sha1"/ s|$| [Published]|" "$1")" >"$1"
+		fi
+	done
+}
+
 case "$action" in
 continue)
 	# do we have anything to commit?
@@ -857,6 +871,7 @@ fi
 
 test -s "$todo" || echo noop >> "$todo"
 test -n "$autosquash" && rearrange_squash "$todo"
+warn_published "$todo"
 cat >> "$todo" << EOF
 
 # Rebase $shortrevisions onto $shortonto
@@ -869,6 +884,8 @@ cat >> "$todo" << EOF
 #  f, fixup = like "squash", but discard this commit's log message
 #  x, exec = run command (the rest of the line) using shell
 #
+# Warning: [Published] means that the commit has already been published
+#
 # These lines can be re-ordered; they are executed from top to bottom.
 #
 # If you remove a line here THAT COMMIT WILL BE LOST.
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 025c1c6..f7c31c1 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -755,4 +755,30 @@ test_expect_success 'rebase-i history with funny messages' '
 	test_cmp expect actual
 '
 
+test_expect_success 'warn before rewriting published history' '
+	test_when_finished "rm -rf git.git git" &&
+	git init git.git &&
+	git clone git &&
+	(
+		cd git &&
+		test_commit one_commit main.txt one_commit &&
+		test_commit two_commit main.txt two_commit &&
+		test_commit three_commit main.txt three_commit &&
+		git push --all &&
+		test_commit four_commit main.txt four_commit &&
+		FAKE_LINES="1 2 3" &&
+		export FAKE_LINES &&
+		tmp=$(git rebase -i HEAD~3 | sed -n 2,4p) &&
+		echo "$tmp" >actual &&
+		tmp=$(git cherry --abbrev=7 HEAD~3 | sed -e 's/+[[:space:]]//g') &&
+		two_sha1=$(echo "$tmp" | sed -n 1p) &&
+		three_sha1=$(echo "$tmp" | sed -n 2p) &&
+		four_sha1=$(echo "$tmp" | sed -n 3p) &&
+		echo "pick $two_sha1 two_commit [Published]" >expected &&
+		echo "pick $three_sha1 three_commit [Published]" >>expected &&
+		echo "pick $four_sha1 four_commit" >>expected &&
+		test_cmp expected actual
+	)
+'
+
 test_done
-- 
1.7.8