subtree: fix "git subtree split --rejoin"
"git merge" in v2.9 prevents merging unrelated histories.
"git subtree split --rejoin" creates unrelated histories when
creating a split repo from a raw sub-directory that did not
originate from an invocation of "git subtree add".
Restore the original behavior by passing --allow-unrelated-histories
when merging subtrees. This ensures that the synthetic history
created by "git subtree split" can be merged.
Add a test to ensure that this feature works as advertised.
Reported-by: Brett Cundal <brett.cundal@iugome.com>
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index 7a39b30..b567eae 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -662,6 +662,7 @@
debug "Merging split branch into HEAD..."
latest_old=$(cache_get latest_old)
git merge -s ours \
+ --allow-unrelated-histories \
-m "$(rejoin_msg "$dir" $latest_old $latest_new)" \
$latest_new >&2 || exit $?
fi
