revision: use repository from rev_info when parsing commits

revision: use repository from rev_info when parsing commits

This is needed when repo_init_revisions() is called with a repository
that is not the_repository to ensure appropriate repository is used
in repo_parse_commit_internal(). If the wrong repository is used,
a fatal error is the commit-graph machinery occurs:

  fatal: invalid commit position. commit-graph is likely corrupt

Since revision.c was the only user of the parse_commit_gently
compatibility define, remove it from commit.h.

Signed-off-by: Michael Forney <mforney@mforney.org>
Acked-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>