Merge branch 'rs/pull-signed-tag' into maint

When "git merge-recursive" works on history with many criss-cross merges in "verbose" mode, the names the command assigns to the virtual merge bases could have overwritten each other by unintended reuse of the same piece of memory. * rs/pull-signed-tag: commit: use FLEX_ARRAY in struct merge_remote_desc merge-recursive: fix verbose output for multiple base trees commit: factor out set_merge_remote_desc() commit: use xstrdup() in get_merge_parent()