[PATCH v2] rerere: fix crash during clear

When rerere_clear is called, for instance when aborting a rebase, and the current conflict does not have a pre or postimage recorded git crashes with a SEGFAULT in has_rerere_resolution when accessing the status member of struct rerere_dir. This happens because scan_rerere_dir only allocates the status field in struct rerere_dir when a post or preimage was found. In some cases a segfault may happen even if a post or preimage was recorded if it was not for the variant of interest and the number of the variant that is present is lower than the variant of interest.

Solve this by making sure the status field is large enough to accommodate for the variant of interest so it can be accessed without checking if it is large enough.

An alternative solution would be to always check before accessing the status field, but I think the chosen solution aligns better with the assumptions made elsewhere in the code.

Signed-off-by: Marcel Röthke <marcel@roethke.info>
---
Range-diff against v1:
1:  93f982d170 ! 1:  68178298fe rerere: fix crash in during clear
    @@ Metadata
     Author: Marcel Röthke <marcel@roethke.info>
     
      ## Commit message ##
    -    rerere: fix crash in during clear
    +    rerere: fix crash during clear
     
         When rerere_clear is called, for instance when aborting a rebase, and
         the current conflict does not have a pre or postimage recorded git
    @@ Commit message
         the number of the variant that is present is lower than the variant of
         interest.
     
    -    This patch solves this by making sure the status field is large enough
    -    to accommodate for the variant of interest so it can be accesses without
    +    Solve this by making sure the status field is large enough to
    +    accommodate for the variant of interest so it can be accessed without
         checking if it is large enough.
     
         An alternative solution would be to always check before accessing the
    @@ rerere.c: static void read_rr(struct repository *r, struct string_list *rr)
      		buf.buf[hexsz] = '\0';
      		id = new_rerere_id_hex(buf.buf);
      		id->variant = variant;
    -+		/* make sure id->collection->status has enough space
    -+		 * for the variant we are interested in */
    ++		/*
    ++		 * make sure id->collection->status has enough space
    ++		 * for the variant we are interested in
    ++		 */
     +		fit_variant(id->collection, variant);
      		string_list_insert(rr, path)->util = id;
      	}

 rerere.c | 5 +++++
 1 file changed, 5 insertions(+)