This introduces additional method for linting,
to reduce the complexity of `lint_commits`.

Make danger pick reviewers and maintainers at random, for feontend,
backend, database, etc, changes, whenever files belonging to those
teams get changed.

- Also pulls URLs into vars

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

Rename ~Packaging label to ~Package

This danger check utilises `yarn-deduplicate` in order to show duplicate
dependencies in the yarn.lock dependency tree.
Often when introducing new dependencies or updating existing ones, yarn
does not seem to build the most optimal dependency tree.

In order to prevent those unnecessary dependency updates we are nudging
developers and maintainers to resolve these issues in MRs. Automating
this with danger especially helps, as yarn.lock files are not that easy
to review.

Namely the `ci-build` and `meta` labels.
Signed-off-by: Rémy Coutable <remy@rymai.me>

This adds a Danger check to produce a warning for MR titles greater than
72 characters. This is necessary because when squash on merge is used,
the MR title will be used for the commit message (at least by default).
This in turn leads to commit messages that violate our commit message
guidelines.

For more information, refer to
https://gitlab.com/gitlab-org/release/framework/issues/24.

We have a Danger check that warns if you made changes in app/ but not in
spec/. However, this only checked for changed files - not new files. If
you added an app file with no specs, it wouldn't warn; and it would warn
erroneously if you added a missing spec file while changing a file in
app/.

Danger apparently has three different objects which could contain files
you often want to check:

 - git.added_files
 - git.modified_files
 - git.renamed_files

The problem: If a file is renamed, `modified_files` contains the file
path before the rename. In some Danger checks we use `added_files` +
`modified_files`, which might contain the deleted paths of renamed
files, but missing the new paths of renamed files.

So we need to consider `renamed_files` as well.

We disabled a lot of eslint rules on a per-file basis. This checks
touched files for those and reminds you to re-enable the rules and fix
them.

This adds a Dangerfile which executes `prettier` to find out if someone
touched Frontend files and forgot to run it on their current branch.

This changes the hard limit of 50 to a soft limit of 50, with the new
hard limit being 72 characters. This gives people a bit more space,
while still (hopefully) guiding them towards subject lines that are
roughly 50 characters long.

Fixes https://gitlab.com/gitlab-org/release/framework/issues/16

This changes our Danger integration so that it is smarter about
detecting GitLab emoji in commit messages. This is done using a two step
process:

1. We use the old regular expression to determine if a commit message
   _might_ include an emoji.

2. If this regular expression matches, we then check for all existing
   emoji names in the commit message. This might be a wee bit expensive,
   but because we couple it with the previous step it should be rarely
   executed.

This ensures we don't trigger an error when a commit message includes
text such as `:foo:bar:`, which is not a valid Emoji.

Fixes https://gitlab.com/gitlab-org/release/framework/issues/15

This relaxes the commit rules regarding the number of changed lines.
Previously we required a detailed description if 20 or more lines were
changed. Starting with this commit we change the rules so Danger only
notifies you about writing a detailed description if:

1. A commit changes more than 3 files
2. The same commit changes more than 30 lines

This should make it easier to do a find replace to fix a typo, without
having to repeat what the subject line already says, while still
reminding developers to write a detailed description for new features
and other larger changes.

Fixes https://gitlab.com/gitlab-org/release/framework/issues/13

This Dangerfile ensures that commit authors write good commit messages.
We also prevent the use of Emoji, since these add no value and may not
always be displayed properly.

Merge commits are currently ignored. In the future we most likely want
to stop using these, but this is a separate discussion, hence we ignore
them for the time being.

The rules enforced by this Dangerfile are based on the article found at
https://chris.beams.io/posts/git-commit/. For more information, refer to
https://gitlab.com/gitlab-org/gitlab-ce/issues/50003.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/50003

Every time a doc change is made, a comment to
ping the @gl-docsteam is added.

If it's most of the time, then it's not all.

It's possible for a Ruby file to be empty and thus `gets` returns `nil`.

Also indents the Markdown since we're using `<<~` and removes an
unneeded variable.

Checks that new Ruby files will enable
frozen string literal.

Partially addresses #47424.