In case merge request is broken, we shouldn't check if the sha
is mergable, as it will be null, and there's no point, as we know
that it's not mergable.

Fixes #3339

This MR hides the 'Remove source branch' button when a new commit is added to the source branch

Instead of running ClosingIssueExtractor for every commit in a merge
request we can gather all the commit messages (and the merge request
description), concatenate all this together and then run
ClosingIssueExtractor only once.

The result of this is that MergeRequest#closes_issues is now between
3.5x and 4x faster than the old setup. Using a merge request with 10
commits (each referencing a number of issues to close) this reduced the
call duration from around 200 milliseconds to around 50 milliseconds.

As a result of these changes the Jira related tests for
MergeRequest#closes_issues have been removed. These tests stubbed
Commit#closes_issues meaning that the only code that was really tested
was the call to Array#uniq to filter out duplicate issues. As this code
is no longer used (nor present) the corresponding tests were removed.

Related: gitlab-org/gitlab-ce#12419

* Use commit objects instead of IDs when generating diffs
* Use proper references when generating MR's source and target
* Update broken specs

These scopes don't care about the order. Removing the explicit "ORDER
BY" can speed up the queries by a little bit.

This replaces plucking of IDs with a sub-query, saving the overhead of
loading the data in Ruby and then mapping the rows to an Array of IDs.
This also scales much better when dealing with a large amount of IDs
that would be involved.

Get "Merge when build succeeds" to work when commits were pushed to MR target branch while builds were running

Modified changelog

When calling MergeRequest#ci_commit the code would previously raise an
error if the source project no longer existed (e.g. because the user
removed their fork).

See #3599 for more information.

When using IssuableFinder/IssuesFinder to find issues for multiple
projects it's more efficient to use a JOIN + a "WHERE project_id IN"
condition opposed to running a sub-query.

This change means that when finding issues without labels we're now
using the following SQL:

    SELECT issues.*
    FROM issues
    JOIN projects ON projects.id = issues.project_id

    LEFT JOIN label_links ON label_links.target_type = 'Issue'
                          AND label_links.target_id  = issues.id

    WHERE (
        projects.id IN (...)
        OR projects.visibility_level IN (20, 10)
    )
    AND issues.state IN ('opened','reopened')
    AND label_links.id IS NULL
    ORDER BY issues.id DESC;

instead of:

    SELECT issues.*
    FROM issues
    LEFT JOIN label_links ON label_links.target_type = 'Issue'
                          AND label_links.target_id  = issues.id

    WHERE issues.project_id IN (
        SELECT id
        FROM projects
        WHERE id IN (...)
        OR visibility_level IN (20,10)
    )
    AND issues.state IN ('opened','reopened')
    AND label_links.id IS NULL
    ORDER BY issues.id DESC;

The big benefit here is that in the last case PostgreSQL can't properly
use all available indexes. In particular it ends up performing a
sequence scan on the "label_links" table (processing around 290 000
rows). The new query is roughly 2x as fast as the old query.

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

fix this issue(https://gitlab.com/gitlab-org/gitlab-ce/issues/1393).

Add ignore whitespace optoin to Commits Compare view

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