- Migration in Repository#is_ancestor?

`Kaminari.paginate_array` takes some options, most relevant of which is
a `total_count` parameter. Using the `commit_count` for `total_count`
lets us correctly treat the return of `Repository#commits` as a subset
of all the commits we may wish to list.

Addition of a new `Repository#commit_count_for_ref` method was
necessarry to allow the user to start from an arbitrary ref.

Ref #1381

This will be necessary when adding gitaly settings. This version
doesn't make any functional changes, but allows us to include this
breaking change in 9.0 and add the needed extra settings in the future
with backwards compatibility

This hack is needed because of an issue when --follow and --skip
are passed to git log at the same time.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/23062Signed-off-by: NRémy Coutable <remy@rymai.me>

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Backport changes from the EE-only squash implementation, which would
otherwise conflict when merge CE into EE.

<https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1024>

In repositories such as https://github.com/git/git.git, annotated tags can
point to blobs, not necessarily to commits. `Repository` attempts to
return the tags in the order of the commit date, but if a commit is not
available the previous implementation would error due to a `nil` target.
This change modifies the code to use the current time if a commit
is not associated with the given tag.

Closes #27228

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_21626953
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_21626952

Signed-off-by: NRémy Coutable <remy@rymai.me>

We merge repository checks inside it so we don't have to
check it on the call site, and we could also load the commit
for the caller. This greatly reduce code duplication.

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7237#note_20572919