Also cleans up:

• some deprecations to buffer and assert
• ownership model was improperly generated for annotated_commit

Includes PRs from LibGit2:

• Release 0.99
• Release script
• azure: fix ARM32 builds by replacing gosu(1)
• openssl: fix Valgrind issues in nightly builds
• fuzzers: Fix the documentation
• azure: fix misleading messages printed to stderr being
• tests: iterator: fix iterator expecting too few items
• transports: http: fix custom headers not being applied
• azure: fix Coverity pipeline
• azure: tests: re-run flaky proxy tests
• fetchhead: strip credentials from remote URL
• azure-pipelines: properly expand negotiate passwords
• cred: change enum to git_credential_t and GIT_CREDENTIAL_*
• Update link to libgit2 Julia language binding
• Return int from non-free functions
• HTTP: Support Apache-based servers with Negotiate
• internal types: change enums from type_t to _t
• merge: Return non-const git_repository from accessor method
• Do not return free'd git_repository object on error
• refs: refuse to delete HEAD
• index: replace map macros with inline functions
• Make type mismatch errors consistent

Includes unmerged PRs:

• winhttp: support optional client cert libgit2/libgit2#5384
• Support core.longpaths on Windows libgit2/libgit2#5347
• Parallelize checkout_create_the_new for perf libgit2/libgit2#4205