Add test for closed MR without fork

Add view test visibility of Reopen and Close buttons

Fix controller tests and validation method

Fix missing space

Remove unused variables from test

closed_without_fork? method refactoring

Add information about missing fork

When closed MR without fork can't edit target branch

Tests for closed MR edit view

Fix indentation and rebase, refactoring

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>

So we have raw_diffs too

Instead calling diff_collection.count use diff_collection.size which is cache on the diff_collection

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>

When importing a pull request from GitHub, the old and new branches may
no longer actually exist by those names, but we need to recreate the
merge request diff with the right source and target shas.

We use these `target_branch_sha` and `source_branch_sha` attributes to
force these to the intended values. But the reader methods were always
looking up to the target/source branch head instead of check if these
values was previously set.

When rendering a list of diff files, skip those where the diff is over
10 KB and provide an endpoint to render individually instead.

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