[PATCH v4 0/6] Support for commits signed by multiple algorithms

This series introduces support for verifying commits and tags signed by multiple algorithms.

These commits allow for signing commits and tags that can be round-tripped through both SHA-1 and SHA-256. We verify only the signature using the current hash algorithm, since we currently don't rewrite objects.

Changes from v3:
* Fix a double free.

Changes from v2:
* Fix problems with size_t and unsigned long on 32-bit systems by
  creating a cleanup patch at the beginning of the series.
* Fix a clang warning with initialization by using memset.

Changes from v1:
* Fix brown paper bag bug where some tests failed due to a bad rebase.

brian m. carlson (6):
  ref-filter: switch some uses of unsigned long to size_t
  commit: ignore additional signatures when parsing signed commits
  gpg-interface: improve interface for parsing tags
  commit: allow parsing arbitrary buffers with headers
  ref-filter: hoist signature parsing
  gpg-interface: remove other signature headers before verifying

 builtin/receive-pack.c   |  4 +-
 builtin/tag.c            | 16 ++++++--
 commit.c                 | 85 +++++++++++++++++++++++++++-------------
 commit.h                 | 12 +++++-
 fmt-merge-msg.c          | 29 ++++++++------
 gpg-interface.c          | 15 ++++++-
 gpg-interface.h          |  9 ++++-
 log-tree.c               | 15 +++----
 ref-filter.c             | 33 ++++++++++------
 t/t7004-tag.sh           | 25 ++++++++++++
 t/t7510-signed-commit.sh | 43 +++++++++++++++++++-
 tag.c                    | 15 +++----
 12 files changed, 226 insertions(+), 75 deletions(-)