commits from the other repository. We'll cleanup
the tmp ref after we're done with our business.

when we care only about the number of commits

We do not have to instantiate all objects in this case.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6658#note_17190236

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Customers running old versions of GitLab may have MergeRequestDiffs with
the text ["--broken diff"] due to text generated by gitlab_git 1.0.3.
To avoid the Error 500, verify that each element is a type that gitlab_git
will accept before attempting to create a DiffCollection.

Closes #20776

Closes #22438

This way we could also show pipelines from commits which
were discarded due to a force push.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* remove ref fetch (we do it during creation anyway)
* remove safe_head_commit_sha for diff compare (do not depend on the source branch)
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* Add MergeRequestDiff#latest?
* Remove unnecessary variable assignment
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Speedup DiffNote#active? on discussions, preloading noteables and avoid touching git repository to return diff_refs when possible

- Preloading noteable we share the same noteable instance when more than one 
discussion refers to the same noteable.
- Any other call to that object that is cached in that object will be for any 
discussion.
- In those cases where merge_request_diff has all the sha stored to build a diff_refs get that 
diff_refs using directly those sha instead accessing to the git repository to first get the 
commits and later the sha.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* show commits count in the merge request version dropdown
* initialize base/start commit sha for old merge request diffs from repo
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

* Add merge_request_diff validation to merge_request model
* Improve initialize of merge_request_diff object
* Rename some merge_request_diff methods for clarity
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Since MergeRequestDiff is not about branches and current state of merge
request diff anymore I removed most of branch related method and added
validation for head/start/base commit sha. From this point
MergeRequestDiff is about saving diff between branches only once at moment of
creation. Once created MergeRequestDiff should not be changes. Because
of that we should not rely on changes in source/target branches when
read from MergeRequestDiff
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

WIP - trying to replicate UTF-8 error

fix spec

fixing encoding issue and another spec, to do with MR diffs

fix issue and spec failure

Add changelog and bumped up I/E version

fix spec based on feedback - omitted target project