please.sh rebase: record conflict resolutions also for merge commits

When we use the Git garden shears, we often redo merges. Merge conflicts
are quite common for that operation, so we should use rerere for those,
too.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

please.sh

@@ -576,8 +576,12 @@ record_rerere_train () {
 	 cp "$orig_index" "$GIT_INDEX_FILE" &&
 	 git add -u &&
 	 tree4="$(git write-tree)" &&
-	 stopped_sha="$(git rev-parse --git-path rebase-merge/stopped-sha)" &&
-	 stopped_sha="$(cat "$stopped_sha")" &&
+	 if ! stopped_sha="$(git rev-parse --git-path \
+			rebase-merge/stopped-sha)" ||
+		! stopped_sha="$(cat "$stopped_sha")"
+	 then
+		stopped_sha="$(git rev-parse -q --verify MERGE_HEAD)"
+	 fi &&
 	 base_msg="$(printf "cherry-pick %s onto %s\n\n%s\n%s\n\n\t%s" \
 		"$(git show -s --pretty=tformat:%h $stopped_sha)" \
 		"$(git show -s --pretty=tformat:%h HEAD)" \