ll-merge: killing the external merge driver aborts the merge
When an external merge driver dies with a signal, we should not
expect that the result left on the filesystem is in any useful
state. However, because the current code uses the return value from
run_command() and declares any positive value as a sign that the
driver successfully left conflicts in the result, and because the
return value from run_command() for a subprocess that died upon a
signal is positive, we end up treating whatever garbage left on the
filesystem as the result the merge driver wanted to leave us.
run_command() returns larger than 128 (WTERMSIG(status) + 128, to be
exact) when it notices that the subprocess died with a signal, so
detect such a case and return LL_MERGE_ERROR from ll_ext_merge().
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
diff --git a/Documentation/gitattributes.txt b/Documentation/gitattributes.txt
index 02a3ec8..6deb89a 100644
--- a/Documentation/gitattributes.txt
+++ b/Documentation/gitattributes.txt
@@ -1132,7 +1132,10 @@
The merge driver is expected to leave the result of the merge in
the file named with `%A` by overwriting it, and exit with zero
status if it managed to merge them cleanly, or non-zero if there
-were conflicts.
+were conflicts. When the driver crashes (e.g. killed by SEGV),
+it is expected to exit with non-zero status that are higher than
+128, and in such a case, the merge results in a failure (which is
+different from producing a conflict).
The `merge.*.recursive` variable specifies what other merge
driver to use when the merge driver is called for an internal
diff --git a/ll-merge.c b/ll-merge.c
index 07ec16e..ba45aa2 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -243,7 +243,14 @@ static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
unlink_or_warn(temp[i]);
strbuf_release(&cmd);
strbuf_release(&path_sq);
- ret = (status > 0) ? LL_MERGE_CONFLICT : status;
+
+ if (!status)
+ ret = LL_MERGE_OK;
+ else if (status <= 128)
+ ret = LL_MERGE_CONFLICT;
+ else
+ /* died due to a signal: WTERMSIG(status) + 128 */
+ ret = LL_MERGE_ERROR;
return ret;
}
diff --git a/t/t6406-merge-attr.sh b/t/t6406-merge-attr.sh
index 5e4e4dd..b50aedb 100755
--- a/t/t6406-merge-attr.sh
+++ b/t/t6406-merge-attr.sh
@@ -56,6 +56,12 @@
) >"$ours+"
cat "$ours+" >"$ours"
rm -f "$ours+"
+
+ if test -f ./please-abort
+ then
+ echo >>./please-abort killing myself
+ kill -9 $$
+ fi
exit "$exit"
EOF
chmod +x ./custom-merge
@@ -162,6 +168,23 @@
rm -f $o $a $b
'
+test_expect_success 'custom merge driver that is killed with a signal' '
+ test_when_finished "rm -f output please-abort" &&
+
+ git reset --hard anchor &&
+ git config --replace-all \
+ merge.custom.driver "./custom-merge %O %A %B 0 %P" &&
+ git config --replace-all \
+ merge.custom.name "custom merge driver for testing" &&
+
+ >./please-abort &&
+ echo "* merge=custom" >.gitattributes &&
+ test_must_fail git merge main &&
+ git ls-files -u >output &&
+ git diff --name-only HEAD >>output &&
+ test_must_be_empty output
+'
+
test_expect_success 'up-to-date merge without common ancestor' '
git init repo1 &&
git init repo2 &&
